Source: UNIVERSITY OF CALIFORNIA submitted to
BIOLOGY, BEHAVIOR, AND ECOLOGY OF VECTORS OF PLANT PATHOGENS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0154931
Grant No.
(N/A)
Project No.
CA-R-ENT-5397-H
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2006
Project End Date
Sep 30, 2011
Grant Year
(N/A)
Project Director
Perring, T. M.
Recipient Organization
UNIVERSITY OF CALIFORNIA
(N/A)
RIVERSIDE,CA 92521
Performing Department
Entomology, Riverside
Non Technical Summary
This project focuses on insect-vectored plant pathogens, with initial efforts aimed at studies on Pierce's disease (PD) of grapevines. This disease is caused by the bacterium Xylella fastidiosa and is vectored by sharpshooters. An introduction of the glassy-winged sharpshooter (GWSS), Homalodisca coagulata Say, in 1990 into California has resulted in severe epidemics of PD. Currently, we don't know very much about how GWSS moves X. fastidiosa into and within vineyards, and because of this lack of information it is difficult to design long-term management strategies for PD. This project will provide this basic information and allow us to establish economic thresholds for GWSS. In addition, we will develop a comprehensive sampling program based on the distribution of X. fastidiosa within grapevines, within vineyards, and within large geographic areas. With this sampling program, growers will be able to efficiently find infected vines within their vineyards so that actions can be taken to remove these vines.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2111050113010%
2111122113010%
2111460113010%
2120999117010%
2121130117015%
2121131117015%
2121420117010%
2121429117010%
2121499117010%
Goals / Objectives
The PI has interest in several insect-vectored disease projects at the present time, including aphid-vectored potyviruses in cucubits, whitefly-borne criniviruses in strawberry, and PD in grapes. Here we present objectives and procedures for PD, since it is one of the most pressing disease problems in California agriculture at the present time. It also serves as a model system and many of the techniques that are proposed for studying PD can be applied to other pathogen systems. 1. Determine the relationship between different densities of H. coagulata and X. fastidiosa primary spread and use this information to calculate an economic injury level. 2.Determine the relationship between H. coagulata and X. fastidiosa secondary spread and use this information to evaluate grapevine roguing as a management tactic. 3.Develop a comprehensive PD sampling program including vine-, areawide-, and vineyard-level PD sampling plans. 4.Elucidate relationships between PD distribution and H. coagulata abundance.
Project Methods
Introductions of new insects into agricultural areas can result in the spread of otherwise innocuous pathogens causing devastating results in certain commodities. Similarly, introductions of an exotic pathogen can lead to disease epidemics when they become transmitted by otherwise innocuous insects. Numerous examples of both exist, but perhaps the most significant in the last 15 years was the introduction of the glassy-winged sharpshooter (GWSS), Homalodisca coagulata Say, which vectored Xylella fastidiosa causing Pierce's disease (PD) in grapes in California. PD was identified in the Temecula Valley of Riverside County in 1997, and by 2002, the disease caused an estimated $13 million prompting the removal of approximately 40% of the vineyard acres. Currently, management strategies for PD attempt to limit both primary and secondary spread. Because the relationship between vector density and pathogen incidence is unknown, treatment thresholds for GWSS have been conservatively based on vector presence in citrus. If the relationship between GWSS density and X. fastidiosa incidence were known, the economic injury level could be calculated. In addition research to determine the PD incidence at which grapevine roguing will prevent pathogen spread is needed. A key component in the development of these management strategies is determining the location of infected vines within a vineyard, and the location of infected vineyards within a large geographic area. Without this knowledge, it is impossible to understand how X. fastidiosa is spread by GWSS and other vectors, or how features of the environment surrounding a vineyard (like other GWSS and PD hosts) impact movement of X. fastidiosa through the vineyard. Also, due to the limitations of the current symptom-based PD surveys, the majority of vineyards in California have never been surveyed for PD. Thus, for most of the state, we don't have any information on the extent of the PD epidemic. This project will develop PD sampling strategies that are not biased by putative symptomology, that are economical so they can be applied to large geographic areas, and that have sufficient detail so they can be used to locate diseased vines within vineyards. Our most recent studies have focused on elucidating the epidemiology of PD and developing a sampling program for PD detection. Epidemiological studies will determine the relative importance of primary and secondary spread which has direct application to management. The results of this work will be used to calculate the economic injury level for H. coagulata as a vector of X. fastidiosa, and to evaluate grapevine roguing as a management tactic to prevent X. fastidiosa spread. For the sampling program, we have identified 'PD-signature' areas in infected vineyards and the current project will investigate the use of remote sensing to locate these areas and prioritize vineyards for intensive sampling. This work will result in a comprehensive sampling program that utilized information gained at the vine, vineyard, and areawide levels.

Progress 10/01/06 to 09/30/11

Outputs
OUTPUTS: In our vector work, we found remote sensing and disease symptomatology can estimate areas for further sampling of Pierces Disease using ELISA. Sampling should include petioles from the most mature leaves on a cane and multiple canes on a plant should be sampled. We identified several modes of transmission of Xylella fastidiosa (Xf) to grapevines including: mechanical through pruning, plant-to-plant using grafts, and by feeding of different species and life stages of plant-sucking insects; however, the highest transmission rate (21.4%) was observed by adult sharpshooters (SS). Although SS preferred young tissues, they spent considerable time feeding on mature canes which may lead to chronic Xf infection. In particular, glassy-winged sharpshooters (GWSS) preferred mature canes during the winter months. Both glassy-winged sharpshooters (GWSS) and smoketree sharpshooters (STSS) were able to transmit XF from alfalfa, annual bluegrass, cheeseweed, sunflower, London rocket, tree tobacco, Blando brome, and white sweetclover into grapes. Species-specific transmission by GWSS from basil into grapes and by STSS from Hykon Rose clover, annual ryegrass and California red oats into grapes also occurred. Numerous plants (cultivated crops, ground covers and weeds) found within and adjacent to vineyards are capable of serving as both reservoirs of Xf infection and food sources for SS, including: alfalfa, basil, lima bean, tomato, goosefoot, Spanish broom, tree tobacco, annual ryegrass, black mustard, Blando brome, New Zealand white clover, Hykon rose clover, cowpea, fava bean, field pea, meadow barley, and California red oats based on greenhouse inoculation studies. In our date studies on carob moth (CM), both center cut thinning and vegetation removal led to reduced CM densities. Clean date gardens reduced spring infestation thereby reducing numbers of CM females ovipositing into pre-harvest dates. Removal of vegetation/debris led to increased mortality of larvae developing in abscised dates. A single sanitation treatment led to decreased infestation; however, moths were found to re-enter from non-treated areas indicating a need for large-scale implementation. Mating disruption using a sex pheromone mimic reduced trap catches and was seen as a viable alternative to multiple applications of malathion with similar application costs and efficacy. Methoxyfenozide (Intrepid) was excellent in controlling CM. A binomial sampling method to use in determination of action thresholds was devised with 150 dates/garden, 10 dates/15 trees collected when dates have turned from green to brown. Spirodiclofen (Envidor) was found to be more effective than Hexythiozox (Savey) against date mites. We described the mating behavior of Bemisia argentifolii and found it to be similar to other whitefly species. Transmission efficacies between isofemale lines of Myzus persicae were found to be significantly different and affected by prior food plant history and duration of host plant use. Stylet penetration also may affect transmission by aphids, particularly during intracellular punctures of plant tissues. PARTICIPANTS: Over this 5 year project a number of cooperators, research scientists, post-graduate researchers, students, and staff researchers have been involved. Jennifer Hashim-Buckey and Murray Pryor with UC Cooperative Extension in Kern County were cooperators who assisted in sampling vineyards for PD. Dr. Matthew Blua was a Research Scientist in the program who participated in the transmission of PD by GWSS. Drs. Rayda Krell and Yong-Lak Park were post-graduate researchers in the laboratory who worked on PD sampling and transmission studies of PD by mechanical means and by insect vectors. Dr. Krell is currently on leave from academia to care for her young family, and Dr. Park is an Assistant Professor at West Virginia University. Dr. Jung-Joon Park was a post-graduate researcher who participated in the PD sampling program and he worked on the carob moth project. Dr. Park has taken a research position in S. Korea. Dr. Justin Nay received his Ph.D. working on carob moth in the program, and Dr. Elizabeth Boyd, also a Ph.D. graduate student in the UC Riverside Entomology Department participated in sampling carob moth in dates. Dr. Nay is a partner in a successful Pest Consulting Business in central California and Dr. Boyd is a Professor at Chico State University. Ms. Emily Symmes earned her M.S. degree in the program working on the transmission of ZYMV by aphid vectors. She recently completed her Ph.D. in the UC Davis Entomology Department. Mr. Jose Ramirez was an M.S. student in Dr. Tom Miller's (UCR professor) laboratory and Dr. Perring help design the project, analyze the data, and interpret the results from one of his MS studies on transformed bacteria for endosymbiotic control of X. fastidiosa. Mr. Ramirez is in a graduate program at Johns Hopkins University. Mr. Chuck Farrar and Ms. Tracy Pinckard were Staff Research Associates in the program working on various aspects of the research. Dr. Darcy Reed, Administrative Specialist, has been instrumental in managing the laboratory in recent years, and Dr. Nilima Castle, Research Scientist, has assisted with pesticide bioassays for carob moth and date mite. In addition, we worked in collaboration with Dr. Matthew Daugherty, Assistant Extension Specialist in the Entomology Department at UCR. The California Date Commission has been active supporters of the carob moth project. In particular, the Commission Chairman, Mr. Albert Keck of Hadley Date Garden, has allowed us to conduct studies on his date gardens. TARGET AUDIENCES: The target audience for the Pierce's disease research is the California grape industry, including wine, table and raisin grape growers. The research was funded, in part, by the California Department of Food and Agriculture Pierce's Disease Board. The carob moth research will benefit the California date growers, and was funded, in part, by the California Date Commission. In addition to the research activities of the PI, he also mentored 6 undergraduate researchers in the lab over the course of this project. Annually, he has taught a large (300-400 student) freshman level class to non-science majors as part of their breath curriculum. He also has served as the faculty mentor for the Entomology Undergraduate club, and been the Entomology Department Faculty Advisory. From January through August, 2010, he took a 50% administrative appointment as the Associate Dean of Recruiting and Student Success for the College of Agriculture and Natural Sciences. On September 1, 2011, he was selected for a 75% administrative appointment as the Associate Vice Provost of Undergraduate Education. In this role, he serves as the Faculty Director of University Honors, the UC Washington DC program, the UC Sacramento program, the Education Abroad Program, and Summer Sessions. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
This project has supported 2 research scientists, 2 post-doctoral scholars, 2 graduate students, and 4 undergraduate students and resulted in 28 publications. 39 presentations were given at professional and growers meetings. Our findings in grapes indicate that remote sensing for foci of infection using symptoms alone is unreliable (<50% accuracy). However, remote sensing coupled with sampling and assessment with ELISA can provide a reliable tool. For sampling, the most mature leaves on multiple canes should be selected. Sharpshooters prefer young tissues but will feed on mature vines likely leading to transmission of PD. Numerous species of plants capable of serving as reservoirs of infection are found in and around vineyards and growers should be aware of the risks of certain plantings and weeds, particularly alfalfa and monitor infections near those areas. Being aware of these potential PD hosts can lead to weed sanitation programs. Studies suggest that we can reduce carob moth survival and development by creating a hot and dry environment within the date garden, potentially by clearing weeds and debris from the garden floor and by facilitating drop of abscised fruit to the warmer, drier garden floor. Malathion dust applications can be eliminated by judicious sampling and use of mating disruption or by using the less disrupting and highly efficacious methoxyfenozide (Intrepid). In addition, our studies with Spirodiclofen (Envidor) showed this to be a more effective material to control date mite than Savey, which has been industry standard for over a decade.

Publications

  • Park, Y.L., Perring, T.M., Krell, R.K., Hashim-Buckey, J.M., and Hill, B. 2011. Spatial distribution of Pierces disease related to incidence, vineyard characteristics and surrounding land use. Journal of Enology and Viticulture. 62: 229-238.
  • Daugherty, M.P., Rashed, A., Almeida, R., and Perring, T.M. 2011. Vector preference for hosts differing in infection status: sharpshooter movement and Xyllela fastidiosa transmission. Ecological Entomology. 36: 654-662.


Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Working on arthropod-borne plant pathogens, we have continued our study of sharpshooter-vectored Xylella fastidiosa, the causal agent of Pierce's disease (PD) in grapes. In collaboration with a new extension entomologist at UCR, we have found that sharpshooters showed preference for healthy grapevine tissue when compared to X. fastidiosa-infected tissue. Individual sharpshooters that spent more time on healthy tissue were less likely to pick up the PD-pathogen, which has implications in the movement of the pathogen in vineyards. In other studies, glassy-winged sharpshooters (GWSS) were able to transmit X. fastidiosa from alfalfa, basil, annual bluegrass, cheeseweed, common sunflower, London rocket, tree tobacco, Blando brome, and white sweetclover into grapes. Similarly the related smoketree sharpshooter (STSS) was able to transmit X. fastidiosa from alfalfa, Blando brome, and Hykon Rose clover, annual bluegrass, cheeseweed, common sunflower, London rocket, tree tobacco, annual ryegrass, California red oats, and white sweetclover. This is a fairly impressive list of crop, ground cover, and weed species that are found in and around vineyards. Growers should be aware of the potential PD reservoir these plants could harbor. We have continued our research on the carob moth, a severe pest of dates. We have evaluated insecticides and identified Methoxyfenozide (Intrepid) as an excellent material for controlling carob moth. We successfully petitioned IR-4 to conduct residue trials on this material and that study was completed in 2010. We hope to have an expanded label to use this material for the 2011 season. To properly utilize this material, we need to develop a sampling protocol for determining the pest density and the economic threshold. We have completed the first aspect of this research, determining that we should count immature carob moths in 150 abscised brown dates, 10 dates from each of 15 palm trees. Sampling should commence after abscised dates in the bunch turn from green to brown, which happens in July. While developing a sampling strategy to time effective insecticides, we also have continued our work toward using mating disruption for carob moth in dates. We have secured a reliable source for a mimic of the carob moth female sex pheromone. Applied in a Specialized Pheromone and Lure Application Technology (SPLAT) we have been successful in shutting down male traps compared to malathion-treated or non-treated blocks. We also have documented statistically lower numbers of infested dates in SPLAT-treated blocks compared to non-treated and similar infestation rates in SPLAT-treated blocks and Malathion treated blocks. This is encouraging, since the SPLAT treatment costs about the same as Malathion applications. A third area of research has been on the date mite, an early season pest of dates. For this work, we have identified a miticide that is statistically more effective than the grower-standard material Hexythiozox (Savey). We have successfully petition IR-4 to conduct residue trials on this new material, Spirodiclofen (Envidor). All of these results were disseminated to date growers at 2 meetings in 2010. PARTICIPANTS: These projects involved a number of cooperators, research scientists, post-graduate researchers, students, and staff researchers. The California Date Commission has been active supporters of the carob moth project. In particular, the Commission Chairman, Mr. Albert Keck of Hadley Date Garden, has allowed us to conduct studies on his date gardens. In my laboratory, Dr. Jung Joon Park, post-doctoral researcher, worked on the carob moth sampling project and the insecticide and miticide studies. Dr. Darcy Reed, Administrative Specialist, was instrumental in leading the field crews this year, and Dr. Nilima Castle, Research Scientist, assisted with pesticide bioassays for carob moth and date mite. In addition, we worked in collaboration with Dr. Matthew Daugherty, Assistant Extension Specialist in the Entomology Department at UCR. TARGET AUDIENCES: The target audience for the Pierce's disease research is the California grape industry, including wine, table and raisin grape growers. The research was funded, in part, by the California Department of Food and Agriculture Pierce's Disease Board. The carob moth research will benefit the California date growers, and was funded, in part, by the California Date Commission. In addition to the research activities of the PI, he also mentored 4 undergraduate researchers in the lab. He taught a large (300 student) freshman level class to non-science majors as part of their breath curriculum. He also served as the faculty mentor for the Entomology Undergraduate club. From January through August he took a 50% administrative appointment as the Associate Dean of Recruiting and Student Success for the College of Agriculture and Natural Sciences. On September 1, he was selected for a 75% administrative appointment as the Associate Vice Provost of Undergraduate Education. In this role, he serves as the Faculty Director of University Honors, the UC Washington DC program, the UC Sacramento program, the Education Abroad Program, and Summer Sessions. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The mitigation of insect-vectored plant pathogens begins with an understanding of the system components. Our work on the reservoir plants within and around vineyards provides the grower with valuable information for managing his vineyard. We have known for some time that alfalfa is a host for X. fastidiosa, and growers are well served to distance their vineyards from alfalfa. However, other plants have been used as ground cover (like Blando brome, white sweetclover, Hykon Rose, annual ryegrass, and California red oats) and growers need to understand that these plants harbor X. fastidiosa, and that sharpshooters can transmit the pathogen from these hosts to grapevines. In addition, cheeseweed, common sunflower, London rocket, and tree tobacco are common weed plants around vineyards and these plants also harbor PD-pathogen that can be transmitted to grapes. Growers should reduce these weeds around their vineyards. The research that has been conducted on carob moth in dates is aimed at reducing the use of Malathion dust, which is applied mostly on a calendar basis. This material is environmentally costly, killing many non-target organisms. At the same time it is unpopular with the public who live in the urban-agriculture interface frequently encompassing date gardens. Our research will provide more effective insecticides than Malathion dust in addition to generating sampling strategies that will guide the judicious use of the new materials. Furthermore, studies on mating disruption are showing this to be a cost-effective alternative to insecticides. With the SPLAT application to the date palm, rather than the date fruit, this offers an environmentally-benign approach. It has taken nearly 2 decades of research to get to the place where the grower community is beginning to accept SPLAT as a viable alternative to Malathion dust.

Publications

  • Putoff, D.P, F.M. Holzer, T.M. Perring, and L. Walling. 2010. Tomato pathogenesis-related protein genes are expressed in response to Trialeurodes vaporariorum and Bemisia tabaci Biotype B feeding. J. Chem. Ecol. 36: 1271-1285.
  • Walker, G.P., T.M. Perring, and T.P. Freeman. 2010. Life History, Functional Anatomy, Feeding and Mating Behavior. Pp. 109-160 in P.A. Stansly and S.E. Naranjo (eds.) Bemisia: Bionomics and management of a global pest. Springer Science, New York.


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: The PI worked with a graduate student on the management of carob moth on dates. We learned that center cut treatments did not alter fruit abscission, but it did reduced carob moth densities by 54 - 97%. Center cut thinning altered the bunch architecture, allowing abscised fruit to fall to the ground, where the moth larvae are susceptible to mortality from predation. Other research consisted of developing a sampling plan for carob moth on dates. Working with a post-doctoral researcher, our analyses suggested that the best sampling plan should consist of abscised brown dates and carob moth immatures using a sample size of 100 dates. After a re-sampling protocol we revised the plan from 100 to 150 dates (15 dates from 10 trees) to improve the precision of the binomial sampling plan. We conducted other studies on mating disruption of carob moth using a pheromone mimic. This research involved undergraduate student helpers and was done in collaboration with a private firm, ISCA Technologies. We have had excellent results with this strategy and ISCA is now in the process of registering the material. We also conducted the second year of an insecticide trial for carob moths as alternatives to Malathion. Other work in dates, with a post-doctoral research scientist, focused on controlling date mite using low volume acaricides as alternative to Savey. Our date research was presented to the California Date Commission at 3 meetings. We determined that glassy-winged sharpshooter (GWSS) choose to feed on young leaf, petiole, and stem tissue. However, they will feed on old stem tissue as well, which logically should result in chronic infection. GWSS adults frequently change position between various tissues through the day, which may contribute to the apparent effectiveness in spreading Xylella fastidiosa. In fall studies both GWSS and smoketree sharpshooter (STSS) fed equally on infected and non-infected grapevine tissue. Further work demonstrated that X. fastidiosa was successfully transmitted by GWSS from alfalfa-to-alfalfa, alfalfa-to-grapevine, basil-to-basil, basil-to-grapevine, tomato-to-tomato, Blando brome-to-Blando brome, Blando brome-to-grapevine and cowpea-to-cowpea. We have determined that STSS can transmit X. fastidiosa between alfalfa plants, from alfalfa to grapevines, between Blando brome plants, from Blando brome to grapevines, and between fava bean plants. In the laboratory, the PI has mentored 1 research scientist, 1 post-doctoral researcher, 2 Ph.D. students, and 4 undergraduate students. He also served as the academic counselor for Entomology graduate and undergraduate students and he was the faculty mentor for the Entomology Undergraduate club. In October, he took a 50% administrative appointment as the Associate Dean of Recruiting and Student Success for the college. Two progress reports on 2 projects were submitted to the California Department of Food and Agriculture (CDFA) in Feb, August, and October. The PI was on Sabbatical Leave from January through mid-June, therefore his normal teaching load was reduced. In the fall quarter, he taught Agricultural Entomology to 11 students. PARTICIPANTS: These projects involved a number of cooperators, research scientists, post-graduate researchers, students, and staff research associates. Dr. Nilima Prabhaker is a research scientist who works with the PI on lab bioassays to evaluate chemicals for date mite and carob moth control. Dr. Jung-Joon Park works primarily on the carob moth project, carrying out the day to day operations of the project. The date work also involved Dr. Justin Nay who received his Ph.D. working with the PI on the carob moth. He is a partner in a successful Pest Consulting Business in central California. Ms. Tracy Pinckard was a Staff Research Associates in the program with primary responsibilities for the host range study of sharpshooter-vectored X. fastidiosa. In addition, there was 1 full-time technical assistant, 2 Ph.D. students, 4 undergraduate students who worked on various aspects of the research. The date research is done in collaboration with various date growers with support from the California Date Commission. TARGET AUDIENCES: The target audience for the Pierce's disease research is the California grape industry, including wine, table and raisin grape growers. The research was funded by the California Department of Food and Agriculture Pierce's Disease Board. The carob moth research will benefit the California date growers as well as the general public in the urban areas surrounding the date agroecosystem. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
All of the research on carob moth in dates is designed to reduce the prophylactic use of Malathion dust, which is used up to 4 times toward the end of the date production season. This practice is environmentally damaging and causes problems in the urban/agriculture interface of this geographic area. The practice of bunch thinning is an easily implemented strategy that significantly reduces the number of abscised fruit that stay in the bunches. These are the very fruit that serve as the major bridging host for carob moth between the overwintering population and the harvestable fruit. Reducing these fruit has a large detrimental impact on the carob moth. Turning to our mating disruption research, this strategy is environmentally benign, which is highly desirable by date growers who struggle with the urban surroundings of their gardens. We have shown that carob moth infestations in mating disruption plots are comparable with those treated with Malathion. Further work will determine the best rate, timing, and placement of the pheromone to maximize the effectiveness and obtain the most economic efficiency of this strategy. At the same time, our cooperator, ISCA Technologies, is taking the pheromone mimic through the registration process. We hope to have this competed by September 2010, in time to use in the current season. To provide even more tools, we have conducted research on alternative chemicals to Malathion. Critical to the use of chemicals or mating disruption strategies is the development of a carob moth sampling plan. This will inform growers on if and when they need to initiate control practices, which will ultimately lead to judicious use of the materials as they come on line. For our Xylella fastidiosa-sharpshooter studies, we have learned that GWSS shows a strong preference for grapevine canes from infected vines in the winter months. This aspect of GWSS biology contributes to its status as a vector of X. fastidiosa in grapevines. If we can determine the cause of this preference, we may be able to design methods to reduce it. This work and all research on sharpshooter behavior is valuable to our understanding of how GWSS and STSS transmit X. fastidiosa to grapevines.

Publications

  • Nay, J.E. and T.M. Perring. 2009. Effect of center cut strand thinning on fruit abscission and carob moth, Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae), infestation in California date gardens. J. Econ. Entomol. 102: 948-953.
  • Perring, T.M., J.J. Park, T. Pinckard, R. Gorves, M. Sisterson, C. Farrar. 2009. Seasonal transmission of Xylella fastidiosa by the glassy-winged sharpshooter from grapevines: Sharpshooter preference for infected grapevine tissue. Pp. 181-186 in Esser, T. (ed.) Proceedings, 2009 Pierce's Disease Research Symposium. CDFA, Sacramento, Ca.
  • Perring, T.M. and T.R. Pinckard. Xylella fastidiosa transmission by glassy-winged sharpshooters and smoketree sharpshooters from alternate hosts to grapevine. Pp. 187-191 in Esser, T. (ed.) Proceedings, 2009 Pierce's Disease Research Symposium. CDFA, Sacramento, Ca.
  • Park, J.J. and T.M. Perring. 2010. Development of a binomial sampling plan for carob moth (Lepidoptera: Pyralidae), a pest of California dates. J. Econ. Entomol. Accepted for publication 1 March, 2010


Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: We compared the susceptibility of 2 table grape cultivars to Xylella fastidiosa (Xf) and Pierces disease (PD). The PI worked with a graduate student in a colleague's lab to study the fate of a transformed bacterium in the foregut of the glassy-winged sharpshooter (GWSS). We studied the feeding biology of GWSS on mature grapevines using choice and no-choice studies in the winter, summer and fall. We evaluated common plants that are found close to vineyards as sources of Xf from which GWSS and smoketree sharpshooters can acquire and transmit Xf into grapevines. We completed our survey of table grape vineyards in Kern and Tulare Counties using satellite imagery to search for consecutive missing vines in the vineyards which created "holes" that are visible on the imagery. With this technique we surveyed 66,013 acres in Kern Co. and 37,222 acres in Tulare Co. We also participated in a project with colleagues from West Virginia University using unmanned aerial vehicles for real-time remote sensing for PD sampling. In other vector research, we related stylet penetration feeding behavior of aphids to successful transmission of a plant virus. In dates, we conducted an insecticide trial for carob moths and we evaluated the use of a carob moth pheromone mimic as an alternative to malathion. We also developed a laboratory bioassay and evaluated miticides for use against the date mite. In the laboratory, the PI mentored 2 research scientists, 1 post-doctoral researcher, 2 Ph.D. students, and 4 undergraduate students. He also served as the academic counselor for Entomology graduate and undergraduate students and he was the faculty mentor for the Entomology Undergraduate club. His lab collaborated with another faculty member on a project on GWSS transmission to plants targeted to improve biological control in vineyards. Information has been disseminated in a variety of ways other than publications. Three progress reports on 2 projects were submitted to the California Department of Food and Agriculture (CDFA) in Feb, August, and October and a comprehensive summary of research conducted from 2000-2008 in collaboration with the California Date Commission (CDC) was provided in support of their marketing order renewal. Research results also have been delivered to scientific audiences at the Entomological Society of America annual meeting (2 posters presented) and at the CDFA annual PD-GWSS symposium (2 posters presented). Additional research summaries were presented to growers at CDC meetings on 30 April, 29 May and 30 October and to pest control professionals at the California Association of Pest Control Advisors symposium on 28 May. The PI also participated in field days for new UC President Dynes and Vice-President Dooley (18 January) and another tour for new UCR Chancellor White and UCR Dean Baldwin (12 December) by providing a 1 hr. presentation on date pests in the Coachella Valley. In the formal classroom, the PI taught a seminar in Integrated Pest Management (8 students) and the Natural History of Insects (240 students). He also served at an editor for the J. Econ. Entomol., and on a grant review panel for the California Grape Consortium. PARTICIPANTS: These projects involved a number of cooperators, research scientists, post-graduate researchers, students, and staff research associates. Ms. Jennifer Hashim-Buckey from the UC Cooperative Extension in Kern County and her staff assisted us in sampling vineyards for PD. Dr. Matthew Blua was a Research Scientist in the program who participated in the transmission of PD by GWSS. Drs. Rayda Krell and Yong-Lak Park were post-graduate researchers who worked on grape cultivar susceptibility to PD and PD sampling. Dr. Park is an Assistant Professor at West Virginia University and he continues to collaborate with Dr. Perring on PD sampling. Dr. Jung-Joon Park participated in the PD sampling program and he has worked on the carob moth project. Dr. Park continues to study in the program. Dr. Justin Nay received his Ph.D. working on carob moth. He is a partner in a successful Pest Consulting Business in central California. Ms. Emily Symmes earned her M.S. degree in the program working on the transmission of ZYMV by aphid vectors. Currently she is in a Ph.D. program in the UC Davis Entomology Department. Mr. Jose Ramirez was an M.S. student in Dr. Tom Miller's (UCR professor) laboratory and Dr. Perring help design the project, analyze the data, and interpret the results from one of his MS studies on transformed bacteria for endosymbiotic control of X. fastidiosa. Mr. Ramirez is in a graduate program at Johns Hopkins University. Mr. Chuck Farrar and Ms. Tracy Pinckard were Staff Research Associates in the program working on various aspects of the research. Ms. Pinckard continues to work in the program. TARGET AUDIENCES: The target audience for the Pierces disease research is the California grape industry, including wine, table and raisin grape growers. The carob moth research will benefit the California date growers. The research on aphid borne viruses is largely aimed at the scientific community of plant-arthropod vector researchers. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
We found that Redglobe plants were more susceptible to Xylella fastidiosa (Xf) infection and subsequent development of Pierce's disease (PD) leading to plant death than Thompson Seedless plants. This is the first study to compare PD susceptibility in table grapes varieties. Growers should be cautious because cultivars that can be infected by X. fastidiosa (Xf) but are slow to die may play a role in PD epidemiology by serving as inoculum sources for insect vectors. In research on a transformed symbiotic bacterium, Alcaligenes xylosoxidans var. denitrificans (S1Axd), we determined that S1Axd was able to survive in the foregut of the glassy-winged sharpshooter (GWSS) for at least 12 days. However, S1Axd was a poor colonizer of the sharpshooter foregut, suggesting that it is not a good candidate to pursue for symbiotic control of Xf. Studies found that GWSS males and females chose to feed on young leaf, petiole, and stem tissue compared to the same tissues on older parts of the cane. However, there was substantial time spent feeding on old stem tissue, a phenomenon that would result in more rapid chronic infection than feeding on young tissue. In transmission tests, we were unable to recover Xf from bell pepper, cotton, sunflower, horseweed, annual fescue (Zorro), birdsfoot trefoil, or sudangrass plants. Xylella fastidiosa was successfully isolated from needle-inoculated alfalfa, basil, lima bean, tomato, goosefoot, Spanish broom, tree tobacco, annual ryegrass, black mustard, Blando brome, New Zealand white clover, Hykon rose clover, cowpea, fava bean, field pea, meadow barley, and California red oats. We found STSS transmitted Xf between fava bean plants, between alfalfa plants, and from alfalfa to grapevines and we confirmed successful transmission of Xf by GWSS for cowpea-to-cowpea and tomato-to-tomato. We are still processing data from our PD sampling study using satellite imagery, but preliminary results look positive. We believe this can be used to survey large vineyards and prioritize those that should be sampled. Research on aphid-borne virus found that differences in virus transmission efficiencies were related to the feeding behavior during stylet penetrations of the host plant, particularly behaviors that occur during intracellular punctures. Regarding the work on carob moth, the highest fecundity came from females that spent their larval stage in date fruit that occur early in the season. This is precisely the cohort of individuals that ultimately infest harvestable fruit later in the season. We developed a degree day model from developmental rate data that is useful for timing insecticide applications. This can reduce the pesticide load and improve moth management. Our research on carob moth pheromone mimic indicates that this is a viable alternative to malathion dusting. With a single application, trap shutdown was obtained from early September through harvest in late October. During this time, the standard treatment would be 3-4 applications of malathion dust. Infest data indicated that the mimic-treated plots were similar to the malathion plots.

Publications

  • Krell, R.K., Perring, T.M., Hashim-Buckey, J.M., and Pinckard, T.R. 2008. Susceptibility of Vitis vinifera L. cv. Redglobe and Thompson Seedless to Pierces disease. Am. J. Enol. Vitic. 59: 61-66.
  • Nay, J.E. and Perring, T.M. 2008. Blue Palo Verde, Parkinsonia florida (Benth. ex Grey) S. Wats. (Fabaceae), a new host of the introduced carob moth, Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae), in southern California. Pan-Pacific Entomologist 82: 143-145.
  • Perring, T.M., Farrar, C.A., and Blua, M.J. 2008. Seasonal transmission of Xylella fastidiosa by the glassy-winged sharpshooter from grapevines infected for various lengths of time. Pp. 43-48 in Esser, T. (ed.) Proceedings, 2008 Pierces disease research symposium. California Department of Food and Agriculture, Sacramento, CA.
  • Perring, T.M., Pinckard, T.R., and Farrar, C.A.. 2008. Xylella fastidiosa transmission by glassy-winged sharpshooters and smoketree sharpshooters from alternate hosts to grapevine. Pp. 231-234 in Esser, T. (ed.) Proceedings, 2008 Pierces disease research symposium. California Department of Food and Agriculture, Sacramento, CA.
  • Nay, J.E. and Perring, T.M. 2008. Influence of Host Plant Stages on Carob Moth (Lepidoptera: Pyralidae) Development and Fitness. Environmental Entomol. 37: 568-574.
  • Symmes, E.J., Walker, G.P., and Perring, T.M. 2008. Stylet penetration behaviors of Myzus persicae related to transmission of zucchini yellow mosaic virus. Entomol. Exp. Appl. 129: 258-267.
  • Ramirez, J. L., Perring, T.M., and Miller, T.A. 2008. Fate of genetically modified bacterium in the foregut of glassy-winged sharpshooter. J. Econ. Entomol. 101: 1519-1525.


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: The lab has continued studies on the epidemiology of sharpshooter vectored XYLELLA FASTIDIOSA (Xf), the causal agent of Pierce's disease (PD). We studied 4 potential mechanisms of transmission to grapevines. No Xf transmission by natural root grafts was detected. One of 21 transmission attempts with pruning shears resulted in Xf transmission. Three of 24 smoketree sharpshooter (STSS) nymphs and 3 of 14 adults transmitted Xf. One of 12 transmission attempts by the apache cicada resulted in Xf transmission. We also initiated studies to define specific orientation and feeding behaviors by the glassy-winged sharpshooter (GWSS). We found that both males and females preferred immature tissues to mature tissues on Cabernet Sauvignon and Chardonnay grapevines, yet sharpshooters moved frequently throughout the day. Immature stems and leaves were consistently the most used tissue, while immature petioles and mature stems and petioles were the least used. We have initiated work to evaluate plants found in and around vineyards as hosts for PD. Buckwheat is a host for Xf and sharpshooters acquired from buckwheat and transmitted to grapevines. Tomato, cowpea, and fava bean all sustained infections of X. fastidiosa. Sharpshooters transmitted Xf from infected tomato to tomato and grapevine, from infected cowpea into cowpea and grapevine, and from infected fava bean into fava bean and grapevine. Other work on sampling PD in the field used aerial imagery to locate large "PD signature areas." We have searched 30,353 vineyard acres in Kern and Tulare Counties, identifying 76 vineyards for sampling. We have samples 17 of these vineyards, finding PD in 8 of them. In studies on the carob moth, ECTOMYELOIS CERATONIAE, a pest of dates, we found that there was a significant reduction in the number of moth-infested fruit after a single sanitation treatment. Analyzing the pattern of re-infestation by moths with spatial analysis with distance indices (SADIE), we found significant spatial associations between abscised fruit and moth-infested fruit. The sanitation treatments caused significant gaps in both abscised fruit and moth-infested fruit. Over time, gap sizes became smaller, indicating a non-random pattern of re-infestation that was caused by the movement of moths from non-treated areas into treated areas. Work on aphid-borne viruses found substantial differences in transmission efficiency of 2 isofemale lines of MYZUS PERSICAE collected from and reared on 2 host plants. Experiments showed that aphids continuously reared on okra and those that were reared on okra and allowed a 24-hour pre-acquisition feeding period on mustard had significantly lower transmission than aphids continuously maintained on mustard. Aphids reared on mustard and allowed a 24-hour pre-acquisition feeding period on okra had intermediate transmission efficiency. In long-term host association studies, we found that aphids reared on mustard had significantly higher transmission efficiency than those reared on okra, and aphids reared first on okra and then switched to mustard had a transmission efficiency that was intermediate and not significantly different from the other two treatments. PARTICIPANTS: These projects involved a number of cooperators, post-graduate researchers, students, and staff research associates. Jennifer Hashim-Buckey and Murray Pryor work with UC Cooperative Extension in Kern County and they were cooperators who assisted in sampling vineyards for PD. Dr. Matthew Blua is a Research Scientist in the program who has participated in the transmission of PD by GWSS. Drs. Rayda Krell and Yong-Lak Park were post-graduate researchers in the laboratory who worked on PD sampling and transmission studies of PD by mechanical means and by insect vectors. Dr. Krell is currently on leave from academia to care for her young family, and Dr. Park is an Assistant Professor at West Virginia University. Dr. Jung-Joon Park has participated in the PD sampling program and he has worked on the carob moth project. Dr. Park continues to study in the program. Dr. Justin Nay received his Ph.D. working on carob moth in the program, and Dr. Elizabeth Boyd, also a Ph.D. graduate student in the UC Riverside Entomology Department participated in sampling carob moth in dates. Dr. Nay is a partner in a successful Pest Consulting Business in central California and Dr. Boyd is a post-doctoral researcher working for the Dr. Kent Daane of UC Davis. Ms. Emily Symmes earned her M.S. degree in the program working on the transmission of ZYMV by aphid vectors. Currently she is in a Ph.D. program in the UC Davis Entomology Department. Mr. Chuck Farrar and Ms. Tracy Pinckard are Staff Research Associates in the program working on various aspects of the research. TARGET AUDIENCES: The target audience for the Pierce's disease research is the California grape industry, including wine, table and raisin grapes. The carob moth research will benefit the California date growers. The research on aphid borne viruses is largely aimed at the scientific community of plant-arthropod vector researchers.

Impacts
Our findings of mechanical transmission and insect transmission of X. fastidiosa by STSS nymphs, and an apache cicada adult represent new means of transmission of the pathogen to grapevines. These results highlight the need to consider all means of transmission in the development of PD management programs. GWSS adults prefer to feed on young tissue over older tissue in both summer and winter field studies, and this may impact seasonal spread of bacteria in vineyards. We are evaluating the importance of various crops, cover crops and weeds that are found near vineyards as sources of Xf. Identifying these plants enables growers to target them as a mechanism to reduce spread. Tomato, cowpea, and fava bean can serve as sources, and since cowpea and fava bean are used as cover crops in vineyards, we suggest caution in using these plants. Our sampling studies for PD provide the first step toward sampling large areas for PD, providing the foundation for a statewide PD sampling program. In dates, our work suggests that in-season bunch sanitation could be effective at reducing carob moth densities if applied on a large regional scale. Work on aphid-borne plant viruses suggests that in order to accurately assess the transmission capability of ZYMV, multiple aphid clones should be examined. Furthermore, studies indicate that the host plant on which the aphid is reared as well as the host plant on which it feeds just prior to virus acquisition contribute to transmission efficiency.

Publications

  • Perring, T.M., T.R. Pinckard, and C.A. Farrar. 2007. Xylella fastidiosa transmission by glassy-winged sharpshooters and smoketree sharpshooters from alternate hosts to grapevine. Pp. 268-270 in Esser, T. (ed.) Proceedings, 2007 Pierce's disease research symposium. California Department of Food and Agriculture, Sacramento, CA.
  • Perring, T.M., C.A. Farrar, J.J. Park, T.R. Pinckard, J. Hashim-Buckey, and M.P. Pryor. 2007. Finding Pierce's disease infected vines in large vineyards: A proposed Pierce's disease sampling program. Pp. 225-227 in Esser, T. (ed.) Proceedings, 2007 Pierce's disease research symposium. California Department of Food and Agriculture, Sacramento, CA.
  • Krell, R.K., E.A. Boyd, J.E. Nay, Y.L. Park and T.M. Perring. 2007. Mechanical and insect transmission of Xylella fastidiosa to Vitis vinifera. Am. J. Enology and Viticulture. 58: 211-216.
  • Nay, J.E., Y.L. Park, and T.M. Perring. 2007. Effect of bunch sanitation on spatial distributions of abscised fruit and phycitine moths (Lepidoptera: Pyralidae) in California date gardens. J. Econ. Entomol. 100: 1773-1780.
  • Symmes, E.J. and T.M. Perring. 2007. Intraspecific variation in zucchini yellow mosaic virus transmission by Myzus persicae (Sulzer) and the impact of aphid host plant. J. Econ. Entomol. 100: 1764-1772.
  • Perring, T.M., C.A. Farrar, and M.J. Blua. 2007. Seasonal transmission of Xylella fastidiosa by the glassy-winged sharpshooter from grapevines infected for various lengths of time. Pp. 54-57 in Esser, T. (ed.) Proceedings, 2007 Pierce's disease research symposium. California Department of Food and Agriculture, Sacramento, CA.


Progress 01/01/06 to 12/31/06

Outputs
We have continued studies on the epidemiology of sharpshooter vectored Pierce's disease (PD). We determined that the glassy-winged sharpshooter (GWSS) HOMALODISCA COAGULATA and smoketree sharpshooter (STSS) HOMALODISCA VITRIPENNIS each showed 2 peaks per year and the peaks coincided. Spatial analysis with distance indices (SADIE) showed patches of GWSS located near citrus, and no patch was found in urban landscapes. Major patches of STSS and major gaps of GWSS were located in desert saltbush scrub and urban areas. Studies imply that areawide management targeting specific areas would be possible by identifying the patches and gaps in space and time. In a separate study GWSS adults were consistently active throughout the winter. Early in the study nearly half of the GWSS were caught in citrus crops, 23% were trapped in stone fruit, and 11% in grape. GWSS numbers decreased as distance from citrus increased. After an areawide treatment program was initiated, mean trap count was considerably lower and GWSS-crop associations changed. Active flight of GWSS in the winter, potentially high numbers of sharpshooters carrying XYLELLA FASTIDIOSA (Xf), impact of citrus proximity to sharpshooter densities in other commodities, and the ability to transmit Xf to dormant grapes and almonds, suggests that winter is an important time of the year in the epidemiological cycle of PD. At the grapevine scale, we determined that of the potential PD symptoms, including leaf necrosis and chlorosis, internodal distance, petiole length and weight, cane branching, and matchsticks, only the matchstick symptom was a consistent indicator of infection. We determined that leaves selected from the most basal nodes of positive canes had the highest probability of Xf detection with ELISA. Working toward a sampling program to find PD on the vine, vineyard, and areawide scale, we learned that aggregations of PD are spatially correlated within 26m. In studies on the carob moth, ECTOMYELOIS CERATONIAE, a pest of dates, we found that larval development was substantially reduced in fruit with less than 7.3% moisture content. Maximum predicted development occurred at 20% fruit moisture content. We also developed a cultural management tool which was very effective for removing abscised fruit from bunches. Field testing this tool, we found up to 94% reduction in the number of abscised fruit and a corresponding 99% reduction in the number of carob moth infested fruit compared to the non-treated plots. We have elucidated the mating behavior of the whitefly BEMISIA ARGENTIFOLII and found behaviors similar and distinct to other whitefly species. We hypothesize that the similarities represent evolutionarily conserved behaviors that result in courtships between reproductively incompatible whiteflies and that the differences contribute to prezygotic reproductive isolation among biotypes. From our studies, we propose that the discrimination of signals sent and received from courting whiteflies becomes more intense with each successive phase in the courtship cascade.

Impacts
Studies on sharpshooters indicate that an areawide management program targeting the spatial and temporal distributions should be applied in citrus during the winter months. This will increase management efficiency, maximize economic profit, and insure environmental safety with reduced chemical inputs. We also demonstrated that GWSS should be managed through the winter months to reduce the potential for winter-season transmission of Xf. Additional results showed that PD diagnosis based on foliar symptoms is unreliable, and taking samples from the basal portion of a cane increased the probability of Xf detection. These results are being incorporated into a comprehensive sampling program for monitoring PD in vineyards. Studies suggest that we can reduce carob moth survival and development by creating a hot and dry environment within the date garden, potentially by clearing weeds and debris from the garden floor. This will result in lower moisture content in dates that fall to the ground which extends generation times of larvae inside these dates and increases mortality. Our work also provides an effective method for removing abscised fruit from date bunches, reducing the reliance upon bi-weekly applications of Malathion 5% dust. Whitefly mating behavior studies suggest that signal discrimination may serve to prohibit successful mating, essentially providing a pre-zygotic mechanism leading to reproductive incompatibility among whitefly types.

Publications

  • Krell, R.K., T.M. Perring, C.A. Farrar, Y.L. Park and C. Gispert. 2006. Intraplant Sampling of Grapevines for Pierce's Disease Diagnosis. Plant Disease. 90: 351-357.
  • Park, Y.L., T.M. Perring, C.A. Farrar and C. Gispert. 2006. Spatial and Temporal Distributions of Two Sympatric HOMALODISCA SPP. (Hemiptera: Cicadellidae): Implications for Areawide Pest Management. Agric. Ecosyst. Environ. 113: 168-174.
  • Nay, J. E., and T. M. Perring. 2006. Effect of fruit moisture content on mortality, development, and fitness of the carob moth (Lepidoptera : Pyralidae). Environ. Entomol. 35: 237-244.
  • Perring, T.M. and E.J. Symmes. 2006. Courtship Behavior of BEMISIA ARGENTIFOLII (Hemiptera: Aleyrodidae) and Whitefly Mate Recognition. Ann. Entomol. Soc. Am. 99: 598-606.
  • Park, Y.L., T.M. Perring, R.K. Krell, C.A. Farrar, and C. Gispert. 2006. Spatial Distribution of Pierce's Disease in the Coachella Valley: Implications for Sampling. Am. J. Enol. and Viticulture. 57: 220-225.
  • Nay, J. E., E. A. Boyd, and T. M. Perring. 2006. Reduction of Carob Moth in Deglet Noor Dates Using a Bunch Cleaning Tool. Crop Protection. 25: 758-765.
  • Park, Y.L., T.M. Perring, R. Yacoub, D.W. Bartels, and D. Elms. 2006. Spatial and temporal dynamics of overwintering HOMALODISCA COAGULATA (Hemiptera: Cicadellidae). J. Econ. Entomol. 99: 1936-1942.


Progress 01/01/05 to 12/31/05

Outputs
We continue studying the epidemiology of Pierce's disease (PD), a disease of grapevines resulting from infection of XYLELLA FASTIDIOSA (Xf). This bacterium is vectored by sharpshooters and recent outbreaks have coincided with the glassy-winged sharpshooter (GWSS), HOMALODISCA COAGULATA. Our work has focused on the spatial distribution of Xf within grapevines and within vineyards. At the grapevine scale we found that most visual symptoms of disease were unreliable indicators of Xf infection; only the 'matchstick' symptom was a consistent indicator. We also found that leaves from the most basal nodes of infected canes had the highest probability of Xf detection by ELISA. At the vineyard scale, the spatial structures of PD distributions were characterized with geostatistics and spatial analysis with distance indices (SADIE). In the Coachella Valley, our surveys over 4 years found 97 diseased grapevines from seven vineyards. Fine-grid sampling showed 82% of the diseased vines were adjacent to two to six consecutive dead, missing, or replanted grapevines in a row, suggesting a 'PD-signature.' With remote sensing (natural color and IR images from 2000, 2002, and 2004) we identified 122 signature areas. Ground truthing revealed 57 of the signatures existed and we confirmed the presence of PD-infected vines in 14% of them. This process can be used to prioritize vineyards in large geographic areas for PD sampling. In Kern Country, census data from 215 vineyard blocks showed a total of 52 blocks with PD. 82% of the infected blocks were within 1/4 mile of citrus, an important criterion to consider when sampling for PD in this area. Analyses showed that the distribution of diseased grapevines was dependent on the overall PD incidence in the vineyard. When the incidence was < 0.1%, there was no spatial structure to the infection. Vineyards that had 0.1 - 1% incidence showed a 'trend' distribution pattern, with areas of low to high infection. When the PD incidence was between 1% and 5%, the pattern of disease was random, and it was aggregated when disease incidence was > 5%. In these aggregations, PD-infected vines were spatially correlated within ca. 23-28 m, suggesting an appropriate size for grid sampling plans to find diseased grapevines. We have concluded analyses of a 4-year monitoring study of GWSS and the smoketree sharpshooter (STSS), H. LITURATA. Temporal trap catches of these insects showed two peaks per year, and the peaks of the two species coincided. All patches of GWSS were located near citrus and major patches of STSS and major gaps of GWSS were located in desert saltbush scrub and urban areas. In general, there is a poor relationship between infected fields and numbers of GWSS. Research on the carob moth, ECTOMYELOIS CERATONIAE, a severe pest of dates, showed high moth mortality in dates (up to 99%) that are shaken from the bunch to the ground. We have developed a tool that is effective for removing waste dates from bunches. Studies also showed that moth development and fitness was directly related to the amount of moisture in dates.

Impacts
Our work describes the spatial distribution of PD at the vine, vineyard, and areawide levels, providing the foundation for a comprehensive sampling program. This program impacts three areas of PD management and research. First, it enables growers to locate PD-infected vines that can be rouged. Second, growers will be able to identify problem areas in their vineyards and design local strategies within their vineyard for these areas. Third, the sampling program provides a method for standardizing PD sampling statewide for researchers and policy makers. In other research, we determined that densities of GWSS and STSS in the Coachella Valley were most abundant from January through March and again from May-September. GWSS abundance was highest near citrus while STSS densities were highest near desert saltbush scrub and urban areas. These temporal and spatial relationships should be utilized for the areawide management of the two vector species. Finally, we developed a date bunch cleaning tool that effectively removed abscised dates from bunches. This resulted in up to 99% reduction of carob moth, providing an effective in-season management alternative to insecticidal dust.

Publications

  • Ramirez, J.L., T.A. Miller, T.M. Perring, C. Lauzon, and D. Lampe. 2005. Fate of Xyllela fastidiosa in the foregut of glassy-winged sharpshooters fed on two host plants. Pp. 276-278 in Tariq, M.A., P. Blincoe, M. Mochel, S. Oswalt and T. Esser (eds.) Proceedings of the CDFA Pierce's Disease Research Symposium, Dec. 5-7, 2005, San Diego, CA. Copeland Printing, Sacramento, CA.
  • Nay, J.E. and T. M. Perring. 2005. Impact of ant predation and heat on carob moth (Lepidoptera: Pyralidae) mortality in California date gardens. J. Econ. Entomol. 725-731.
  • Perring, T.M., Y.L. Park, C.A. Farrar, R.K. Krell, B. Hill, M. Kelley, M.P. Pryor, and J. Hashim. 2005. Epidemiological analyses of glassy-winged sharpshooter and Pierce's disease data. Pp. 50-53 in Tariq, M.A., P. Blincoe, M. Mochel, S. Oswalt and T. Esser (eds.) Proceedings of the CDFA Pierce's Disease Research Symposium, Dec. 5-7, 2005, San Diego, CA. Copeland Printing, Sacramento, CA.
  • Perring, T.M., H.S. Costa, and D.A. Cooksey. 2005. Effects of feeding substrate on retention and transmission of Xyllela fastidiosa strains by the glassy-winged sharpshooter. Pp. 124-127 in Tariq, M.A., P. Blincoe, M. Mochel, S. Oswalt and T. Esser (eds.) Proceedings of the CDFA Pierce's Disease Research Symposium, Dec. 5-7, 2005, San Diego, CA. Copeland Printing, Sacramento, CA.
  • Perring, T.M., J. Hashim, C. Gispert, Y.L. Park, C.A. Farrar, R.K. Krell, M.P. Pryor, B. Hill and M. Kelly. 2005. Development of a field sampling plan for glassy-winged sharpshooter vectored Pierce's disease. Pp. 269-272 in Tariq, M.A., P. Blincoe, M. Mochel, S. Oswalt and T. Esser (eds.) Proceedings of the CDFA Pierce's Disease Research Symposium, Dec. 5-7, 2005, San Diego, CA. Copeland Printing, Sacramento, CA.
  • Ramirez, J.L., T.A. Miller, T.M. Perring, C. Lauzon, and D. Lampe. 2005. Fate of a genetically modified bacterium in the foregut of the glassy-winged sharpshooter. Pp. 273-275 in Tariq, M.A., P. Blincoe, M. Mochel, S. Oswalt and T. Esser (eds.) Proceedings of the CDFA Pierce's Disease Research Symposium, Dec. 5-7, 2005, San Diego, CA. Copeland Printing, Sacramento, CA.


Progress 01/01/04 to 12/31/04

Outputs
The major focus in the lab has been the epidemiology of Pierce's disease (PD), a devastating disease of grape caused by an infection of the bacterium, XYLELLA FASTIDIOSA. This bacterium is vectored by a number of sharpshooters, the most significant of which is the glassy-winged sharpshooter (GWSS), HOMALODISCA COAGULATA. Our epidemiological studies seek to understand how GWSS, PD, grapes and the environment interact, with the goal of creating sub-optimal conditions within one or more of these components that leads to a reduction in disease spread. Areawide surveys for PD in the Coachella Valley identified 3 additional fields with PD, bringing the total number of infected fields in this area to 7. In these 7 fields, we have positive identification of 97 vines with PD. GWSS monitoring over the past 4 years showed a dramatic decline between 2002 and 2003 densities, a reflection of wide scale application of pesticides applied to citrus throughout the region. There was generally a poor relationship between infected fields and numbers of GWSS, suggesting that the fields may have been infected with other sharpshooter species, or that the fields were infected prior to our GWSS sampling. We also have completed work on the initial phases of an epidemiological model for predicting PD outbreaks based on densities of GWSS. This model is based on a set of four balanced delay differential equations, two for the GWSS (infected or susceptible) and two equations for grapes (infected or susceptible). Two additional studies have focused on sampling PD within vines and within vineyards. Our vine-sampling research has shown that PD symptom expression on grape leaves is a poor predictor of infection. Within infected canes we have determined that basal leaves are more likely to be positive than distal leaves and combined with our symptom data, we are developing a strategy that will improve our ability to correctly identify infected vines. This work is the first step for developing a field-sampling program. Studies at the field scale indicate that the distribution pattern of PD can be categorized based on overall disease incidence in the field. Vineyards with < 0.1% PD infection showed no detectable spatial structure in PD dispersion. When vineyards had between 0.1% and 1% infection, a random pattern or trend pattern (higher infection toward citrus) existed. When the infection was between 1% and 5%, the spatial pattern of PD was random and when the infection was > 5%, the distribution was clumped. We concluded work on the coconut mite, ACERIA GUERRERONIS, a pest of queen palm seedlings, and we have published the research on the basic biology of this pest. We also have continued our work on the carob moth, ECTOMYELOIS CERATONIAE, a severe pest of dates. We determined that shaking excised dates from the date bunches onto the ground reduces the infestation in date gardens. Mortality in the dropped fruit was attributed to predation by two native ant species, the desert fire ant, SOLENOPSIS AUREA and the California harvester ant, POGONOMYREX CALIFORNICUS, in concert with extreme summer ground temperatures.

Impacts
In the Coachella Valley, we found that numbers of GWSS increased from 2001 to 2002. With the documented increase in numbers of fields with PD, these studies suggest that the areawide spray program implemented by local and state government was necessary and effective. Furthermore, monitoring of GWSS and PD should be continued to insure that the epidemic does not progress in this area. Our epidemiological model, while limited by data gaps in our knowledge of GWSS-vectored PD, is useful for evaluating different components of disease spread. With this analytical tool, it will be possible to model various management strategies and determine their impact before investing in costly field implementation trials. The PD vine sampling research provides a clear methodology for choosing leaves for ELISA testing, the first step toward a field sampling program. On a larger scale, our field sampling work has shown that by knowing the percentage of PD incidence and the location of vineyards relative to citrus, we can predict the distribution pattern of PD in the vineyard. Such inferences about the spatial characterization of PD distributions in vineyards will be used to develop a spatially-oriented sampling program, effectively reducing cost and increasing efficiency of PD sampling. In our carob moth research, we demonstrated high mortality for moth larvae in dates shaken to the date garden floor. This cultural control is the first step toward developing an environmentally sound management strategy that will reduce grower reliance on the use of insecticidal dusts.

Publications

  • T.M. Perring, C. Gispert, C.A. Farrar, R.K. Krell and Y.L. Park. 2004. Area-wide epidemiology of Pierce's disease in the Coachella Valley. Pp. 43-46 in Tariq, M. A., S. Oswalt, P. Blincoe, A. Ba, T. Lorick, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 7-10, 2004, Coronado, CA. Copeland Printing, Sacramento, CA. 391 pp.
  • T.M. Perring, R.K. Krell, C.A. Farrar, Y.L. Park, and C. Gispert. 2004. Improving detection of Pierce's disease infected grapevines. Pp 266-268 in Tariq, M. A., S. Oswalt, P. Blincoe, A. Ba, T. Lorick, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 7-10, 2004, Coronado, CA. Copeland Printing, Sacramento, CA. 391 pp.
  • T.M. Perring, J. C. Allen, C. A. Farrar, R.K. Krell, and Y.L. Park. 2004. Treatment thresholds for the glassy-winged sharpshooter based on the local epidemiology of Pierce's disease spread (a stage-structured epidemic model). Pp. 269-271 in Tariq, M. A., S. Oswalt, P. Blincoe, A. Ba, T. Lorick, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 7-10, 2004, Coronado, CA. Copeland Printing, Sacramento, CA. 391 pp.
  • T.M. Perring, J. Hashim, C. Gispert, Y.L. Park. C.A. Farrar, R.K. Krell, M.P. Pryor, B. Hill, and M. Kelly. 2004. Development of a field sampling plan for glassy-winged sharpshooter-vectored Pierce's disease. Pg. 272-274 in Tariq, M. A., S. Oswalt, P. Blincoe, A. Ba, T. Lorick, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 7-10, 2004, Coronado, CA. Copeland Printing, Sacramento, CA. 391 pp.
  • T. Ansaloni, and T.M. Perring. 2004. Biology of Aceria guerreronis (Acari: Eriophyidae) on queen palm Syagrus romanzoffiana (Arecaceae). Internat. J. Acarol. 30: 63-70.
  • T.M. Perring, Y.L. Park. C.A. Farrar, Krell, R.K., M.P. Pryor, B. Hill, J. Hashim and M. Kelly. 2004. Epidemiological analyses of glassy-winged sharpshooter and Pierce's disease data. Pp. 41-41 in Tariq, M. A., S. Oswalt, P. Blincoe, A. Ba, T. Lorick, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 7-10, 2004, Coronado, CA. Copeland Printing, Sacramento, CA. 391 pp.


Progress 01/01/03 to 12/31/03

Outputs
We have continued research on the greenhouse whitefly, TRIALEURODES VAPORARIORUM, which was a serious problem for vegetable and strawberry growers in Ventura County. We initiated a study to describe factors that result in such large densities of this insect. Of 73 crop and weed plants evaluated, we found 38 plants on which GHWF completed development; 18 of these are new host records. We determined that the majority of GHWF are produced in crop hosts and furthermore that overlapping crop cycles provided a year-round supply of available host material utilized by GHWF. We also discovered that fields close to existing whitefly source fields became infested with immigrating whiteflies at a higher rate than fields not near an infested field. This 'nearest-neighbor' phenomenon can be used by producers on a local scale to prevent seasonal whitefly buildup in their fields. Our epidemiological studies have focussed on the spread of Pierce's disease (PD) bacterium, XYLELLA FASTIDIOSA, by the glassy-winged sharpshooter (GWSS), HOMALODISCA COAGULATA in table grapes. Surveys of the entire Coachella Valley in 2003 bring the total number of locations in the Valley with PD to 3. Yellow sticky traps were used to show the seasonal trend of GWSS adults. Winter traps in 2003 showed higher densities than winter traps in 2002, suggesting an increasing GWSS population density throughout the valley. However, spring and summer 2003 traps were nearly zero at all locations, indicating successful control of GWSS by the CDFA-sponsored vector control program. Through this study, traps adjacent to citrus groves caught more GWSS than traps not near citrus, however fewer than 35 percent of the traps near citrus caught GWSS on any given week. GWSS count data were managed in a GIS format and this enabled us to place relative importance to citrus groves based on various densities of GWSS caught near the groves. This information could be used to target sites for vector reduction treatments. The lab continues to work on the Banks grass mite, OLIGONYCHUS PRATENSIS a pest of date palms PHOENIX DACTILIFERA. We are finishing analyses of data that will establish a sampling plan for this pest. Our work with the coconut mite, ACERIA GUERRERONIS, a pest of queen palm seedlings, SYAGRUS ROMANZOFFIANA also has proceeded to the final analysis stage. In this work we update our last CRIS and report that optimal development occurs at 33.6C. The thermal maximum is 40C and the lower threshold for development is 9.4C. These values were used to determine that 172.7degree days are required for the mite to mature from egg to adult. The mite was found to be arrhenotokous with maximum oviposition of 51 eggs over a 43-day life span. Last, we have continued our studies of the carob moth, ECTOMYELOIS CERATONIAE, a severe pest of dates. We are working on pheromone disruption and this year we evaluated ripe date fruit volatiles as attractants to females. We found 13 compounds in the volatiles from fruit that caused a response. We are following up on these compounds.

Impacts
Greenhouse whitefly has been present in high numbers in the peri-urban agricultural regions of California's southern and central coasts. Problems occur because it is a plant pest, and it is a nuisance to urban dwellers. We have demonstrated that local conditions play a major role, and that vegetable producers can have a direct impact. First, growers should apply systemic insecticides only to fields that are adjacent to potentially infested older fields. The greenhouse whitefly will fly only short distances from infested fields to neighboring crops. This allows growers that are distant from infested fields to avoid unnecessary applications. Second, growers should destroy crop residue immediately after harvest to prevent continued whitefly buildup. Third, growers should maximize the distance between serially planted vegetables. Our epidemiological studies on PD present evidence that the GWSS is more abundant near citrus groves. We also have documented higher disease incidence near groves. This suggests that vector reduction strategies should be done primarily in citrus. However, not all citrus groves are at risk, and we have developed a GIS-based strategy for locating fields that need to be treated. Research on mites continues to elucidate the biology of these occasional pests. From this work, we hope to provide growers alternatives to repeated acaricide application. Regarding our carob moth research, with a female attractant we will be able to attract and kill females, thereby reducing the regular 2-week application of insecticidal dusts.

Publications

  • T.M. Perring, C.A. Farrar, Krell, R.K., and Y.L. Park. 2003. Treatment thresholds for the glassy-winged sharpshooter based on the local epidemiology of Pierce's disease spread. Pp. 104-106 in Tariq, M. A., S. Oswalt, P. Blincoe, R. Spencer, L. Houser, A. Ba, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 8-11, 2003, Coronado, CA. Copeland Printing, Sacramento, CA. 323 Pp.
  • Perring, T.M., C. Gispert, C.A. Farrar, and R.K. Krell. 2003. Epidemiology of Pierce's disease in the Coachella Valley. Pp. 107-110 in Tariq, M. A., S. Oswalt, P. Blincoe, R. Spencer, L. Houser, A. Ba, and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 8-11, 2003, Coronado, CA. Copeland Printing, Sacramento, CA. 323 Pp.
  • Perring, T.M. 2003. Greenhouse whitefly in landscapes. UCCE- Ventura County 'Landscape Entomology Symposium' Abstract book. 3 pp.


Progress 01/01/02 to 12/31/02

Outputs
We have concluded most of our work management of silverleaf whitefly, BEMISIA ARGENTIFOLII. Research has shifted away from whitefly biology to epidemiology of insect-vectored plant pathogens and agriculturally important mites. We see a re-occurrence of greenhouse whitefly, TRIALEURODES VAPORARIORUM, vectored viruses in tomato in southern California. This whitefly has a broad host range and effectively moves from crop to crop throughout the serially-planted agricultural areas. We have determined that greenhouse whitefly is reluctant to leave its host plant and is not prone to take flight as readily as silverleaf whitefly. This lends support for management through crop destruct and rotational programs that create host free barriers in time and space. Other epidemiological studies have focussed on the spread of Pierce's disease (PD) bacterium, XYLELLA FASTIDIOSA, by the glassy-winged sharpshooter (GWSS), HOMALODISCA COAGULATA in table grapes in the Coachella Valley. A significant find this year was the presence of PD in 13 vines from 2 adjacent vineyards in the southeastern part of the Valley. This marks the early stage of the PD epidemic in this area, and puts us in an excellent position to study the development of a GWSS-vectored PD epidemic. We concluded nearly 2 years of area-wide monitoring of GWSS, with several results. First, GWSS numbers appear to be increasing in the area when compared to the same time period as the previous year. Second, GWSS densities are heavy in citrus and almost non-existent in grapes and near urban areas. There is also a declining gradient of GWSS numbers in grapes as trap distance from citrus increases. Third, we have managed our data in a digital GIS, enabling us to identify citrus groves within specified distances of traps that have certain GWSS densities. This is a powerful tool that shows where GWSS management is most needed, as well as groves that are less at risk. In our work on the Banks grass mite, OLIGONYCHUS PRATENSIS we are developing sampling tools and establishing DD models for timing acaricide applications in dates, PHOENIX DACTILIFERA. We continued studies on the coconut mite, ACERIA GUERRERONIS, a pest of queen palm seedlings. We have determined that the mite develops from egg to adult in 6.8 days and that the optimal temperature for development is 29.8C. The thermal optimum is 36.7C. In related research at an infested nursery, large densities of coconut mite were found dispersing through the air via wind. Acaricide trials have failed to identify materials capable of penetrating deep into the meristematic tissue of the plant to provide control. We have continued work on the carob moth, ECTOMYELOIS CERATONIAE, a pest of dates. Our research indicates that moths have retarded development when the moisture level in the fruit drops below 35%. We have found a previously undescribed parasitoid from field collected samples and we will investigate its ecology. We have conducted our first insecticide trial and determined that Dipel and Cryolite provided sufficient control to warrant further investigation. We also are continuing our research into pheromone disruption of carob moth.

Impacts
Our area-wide monitoring programs have elucidated crops and weeds that significantly contribute to area-wide whitefly problems, and when these host plants have the greatest impact. The goal of this work is to provide growers with information that helps them time management strategies in the many crops grown in the regions. Since the arrival of the glassy-winged sharpshooter into California, Pierce's disease has had a major impact on several grape-growing regions in the state. While this disease has been present in California for over 100 years, the arrival of this new sharpshooter has altered the epidemiology. The goal of our epidemiological studies is to identify characteristics unique to regions with high and low PD, and manipulate these features to manage the spread of PD. While the current model is area-wide application of systemic insecticide for GWSS control, it is unlikely that this activity can be sustained because of the cost involved. Our research provides information that will be part of a longer-term management strategy. Our work on mites has continued for many years, however recently there has been an increased interest from growers of numerous commodities facing problems with Acarines. In many systems, the basic biology of the mite is lacking, so the producer is faced with repeated applications of acaracides. The research conducted in our program is aimed at reducing the reliance on these applications toward a more holistic management strategy. Similarly, our work on carob moth will have the same impact.

Publications

  • PERRING, T.M. and FARRAR, C.A. 2002. Whitefly-borne virus epidemiology: lessons learned from the greenhouse whitefly and tomato infectious chlorosis virus. Pp. 104 in in Henneberry, T.J., R.M. Faust, W.A. Jones, and T.M. Perring (eds.) Silverleaf whitefly: National research, action, and technology transfer plan, fourth annual review of the second 5-year plan and final report for 1992-2002. USDA June 2002. 446 pp.
  • PERRING, T.M. and GISPERT, C.A. 2002. Epidemiology of Pierce's Disease in the Coachella Valley. Pp. 70-71 in Tariq, M.A., S. Oswalt, P. Blincoe and T. Esser (eds.) Proceedings of CDFA Pierce's disease research symposium, Dec. 15-18, 2002, San Diego, CA. Digital Logistinx Printing, Sacramento, CA. 177 Pp.
  • PERRING, T. M. 2002. Eriophyoid mites: Special considerations in applied ecological research. Pp. 71-77 in Fernando, L.C.P., G.J. de Moraes, and I.R. Wickramananda (eds.) Proc. Int. Workshop on Coconut mite (Aceria guerreronis). Coconut Research Institute, Lunuwila, Sri Lanka.
  • PERRING, T.M. 2002. Management of Oligonychus pratensis on date palms. Pp. 1-4 in Morales-Malacara, J.B. and G. Rivas (eds.) XI International Congress of Acarology Program and Abstract Book. Universidad Nacional Autonoma de Mexico. 229 pp.
  • GISPERT, C. and PERRING, T.M. 2002. Food preferences of a tydeid mite on date palms in California. Pp 187 in Morales-Malacara, J.B. and G. Rivas (eds.) XI International Congress of Acarology Program and Abstract Book. Universidad Nacional Autonoma de Mexico. 229 pp.
  • ANSALONI, T. and PERRING, T.M. 2002. Biology of Aceria guerreronis Keifer on queen palms. Pp. 145 in Morales-Malacara, J.B. and G. Rivas (eds.) XI International Congress of Acarology Program and Abstract Book. Universidad Nacional Autonoma de Mexico. 229 pp.


Progress 01/01/01 to 12/31/01

Outputs
We have continued to study various aspects of the silverleaf whitefly, BEMISIA ARGENTIFOLII, and its natural enemies. We learned that parasitoids have different foraging behavior and ovipositional rates on different host plants. We showed that glandular trichomes reduced parasitoid walking speeds and residency time, thereby reducing parasitism. These trichomes on velvetleaf entrap parasitoids. Data support the concept of enemy free space for whiteflies on this plant. We also continued work to determine the taxonomic status of whiteflies in the BEMISIA TABACI species complex. We reviewed existing data and created seven groups of whiteflies within the species complex. These groupings follow distinct geographic patterns. Group 1 consists of New World biotypes. Group 2 is cosmopolitan and consists of B biotype (= B. ARGENTIFOLII). Group 3 is from Benin and Spain. Group 4 is from India. Group 5 is from Sudan, Egypt, Spain, and Nigeria. Group 6 is from Turkey, Hainan, and Korea. And group 7 is from Australia. Research on the epidemiology of arthropod-vectored plant pathogens also has continued. Research in collaboration with a colleague in Hungary has described the epidemiology of zucchini yellow mosaic virus in squash. We identified a new aphid vector, APHIS POMI, suggesting squash should not be grown in close proximity to apple, the preferred host of the vector. The lab also has begun work on the glassy-winged sharpshooter (GWSS), HOMALODISCA COAGULATA, and XYLELLA FASTIDIOSA, the bacterial agent causing Pierce's disease (PD) in grapes. In our first study, we determined that grapes grown adjacent to citrus had a higher incidence and severity of PD than grapes more distant from citrus. We also learned that the epidemiology of GWSS-vectored PD occurs at a much larger scale than PD vectored by other leafhoppers. A minimum of 1000 meters is required to study this pathogen system. The lab has continued studies on agriculturally important mites. In our work on the Banks grass mite (BGM), OLIGONYCHUS PRATENSIS we have shown that BGM is resistant to sulfur used to control the mite in dates, PHOENIX DACTILIFERA. The predatory mites, GALENDROMUS MCGREGORI and NEOSEIULUS COMITATUS are negatively impacted by these applications, providing an excellent system for BGM outbreaks. We have initiated studies on the coconut mite, ACERIA GUERRERONIS, a new pest of queen palms in California. This is a difficult research system due to the fastidious nature of the mite, and the requirements of high humidity and a tight environment afforded by the queen palm. We have created a method for studying the mite by imbedding sections of palm tissue into agar, creating a mite feeding chamber that can be observed. The objectives of our work are to describe the biology of the mite on palms, determine how it disperses, and develop management strategies. We have found that the mite disperses in large numbers in the air, so management will be challenging. We have begun work to determine the relationship between mite infestation and the symptom of mite damage and we soon will begin acaricide trials to determine if the mite can be controlled in pots.

Impacts
Our work on BEMISIA is designed to provide information that can be exploited for management of this devastating pest. By understanding the interaction between this herbivore, its predators and various host plants, we hope to identify which plants are beneficial and which are detrimental to crops infested by the whitefly. For example, plants that afford enemy free space by protecting the whitefly and excluding predators should be eliminated from the agricultural ecosystem. Studies on the taxonomy of the BEMISIA species complex further our understanding of outbreak situations in world agriculture. Our epidemiological studies have identified an important vector of zucchini yellow mosaic virus, and important host for vectors of Pierces disease. This information can be used by growers to make decisions about where to plant susceptible crops. Obviously, the crops should be grown distant from potential vector sources. In addition, growers may wish to implement vector control in these alternate crops. Our work on Banks grass mite is aimed at reducing the reliance on chemical control and to develop a biologically-based management program. Based partially on our resistance data, the date growers have switched to a new chemical for date mite control. We are finishing studies on sampling to assist the growers in timing their applications. Many growers do not even know they have the problem. Through our work, we will develop a holistic management strategy. The same can be said for carob moth on dates.

Publications

  • GRUENHAGEN, N.M. and PERRING, T.M. 2001. Plant influences on silverleaf whitefly oviposition and development and the potential for enemy-free space. Entom. Exp. et. Appl. 99: 387-391.
  • PERRING, T. M. 2001. The Bemisia tabaci species complex. Crop Protection 20: 725-737.
  • GISPERT, C., FARRAR, C. and PERRING, T. M. 2001. Seasonal abundance of Banks grass mite, Oligonychus pratensis (Banks) and its natural enemies, and their response to sulfur treatment on commercial date palms, Phoenyx dactilifera L. in southern California. Pp 403-408 in Halladay, R.B., D.E. Walter, H.C. Proctor, R.A. Norton, and M.J. Colloff (eds.) Proc. 10th Int. Cong. of Acarol. CSIRO Publishing, Melbourne, Canberra, Australia.
  • PERRING, T. M., FARRAR, C.A. AND BLUA, M.J. 2001. Proximity to citrus influences Pierce's disease in Temecula Valley vineyards. Calif. Agric. 55: 13-18.
  • GRUENHAGEN, N. M. and T. M. PERRING. 2001. Impact of leaf trichomes on parasitoid behavior and parasitism of the silverleaf whitefly (Homoptera: Aleyrodidae). Southwest Entomol. 26:


Progress 01/02/00 to 12/31/00

Outputs
Considerable effort this year has gone into an evaluation of the systematic relationships of whiteflies in the BEMISIA TABACI species complex. Isoelectric focusing electrophoresis work has elucidated 3 distinct whitefly groups. The first group represents whiteflies collected from the Western Hemisphere, closely associated with Biotype A. The second group consists of whiteflies collected in several geographic regions, all clustering with Biotype B or BEMISIA ARGENTIFOLII. The final group has a single population (Biotype E) collected on a ASYSTASIA GANGETICA from Benin, West Africa. These groupings have been corroborated with other studies in which specific genes were used to create groups and phylogenies of whiteflies in the complex. Further work submitted for publication presents evidence for distinguishing 9 biotypes within the complex, either due to mating incompatibility studies or a combination of other data that serves to separate the biotypes. We are initiating research, using SEM, to identify morphological characteristics of adult whiteflies to assist in our ability to distinguish whiteflies. We are finishing the work on the biology of BEMISIA ARGENTIFOLII natural enemies. A manuscript in press provides data that supports ABUTILON THEOPHRASTI as a plant that offers enemy free space to B. ARGENTIFOLII. Research continues on plant genes in tomato and squash that are up-regulated in response to B. ARGENTIFOLII feeding. Novel genes have been identified in both plants and the functions of these genes are under investigation. Our research on OLIGONYCHUS PRATENSIS, a tetranychid mite pest on dates, PHOENIX DACTYLIFERA, has continued. One manuscript in press documents different levels of sulfur resistance in the mites, while predator mites remain susceptible to treatments. We have shown that spider mite webbing in date bunches is a reliable indicator of mite presence and is linked to damage at the end of the growing season. This work is aimed at providing growers with an effective sampling strategy for timing acaricide application. Biological control studies on this mite-date system have identified two promising candidates, GALENDROMUS MCGREGORI and NEOSEIULUS COMITATUS. We are starting laboratory studies to determine the basic biology of these two predators in preparation of field releases next summer. We also have begun studies into the epidemiology of two arthropod-vectored plant pathogens; Pierce's disease of grapes vectored by HOMALODISCA COAGULATA, and tomato spotted wilt, vectored by FRANKLINIELLA OCCIDENTALIS. Both of these systems are being addressed using geographic information systems based geostatistics that provide excellent analyses of spatially-oriented data. With this work, we have found Pierce's disease incidence to be greater in vines closer to citrus borders, than vines distant from the borders. In the spotted wilt system, we found that epidemics were related to local sources, as opposed to area-wide sources.

Impacts
Research on the systematics of the BEMISIA TABACI species complex is critical to developing management strategies for damaging populations. With the synonymization of 22 distinct species under a single entity, all of the available information on biology and management was lumped. Unfortunately, strategies that work for certain biotypes may not work for others, and our research will enable scientists to cluster information pertinent to specific biotypes. It also will assist us in determining geographic places of origin, so that we can target our search for effective natural enemies. As well, by the recognition that we have distinct biotypes, and in some cases, species within the complex, we can be better prepared for introductions of new types into new geographic areas. Our work on spider mites is aimed at reducing the reliance on chemical control and to develop a biologically-based management program. Finally, the epidemiological studies will generate information that can be used to target measures for mitigating the damage caused by arthropod-vectored plant pathogens.

Publications

  • Walling, L.L., Puthoff, D.P., and Perring, T.M. 2000. Whitefly feeding induces local and systemic changes in tomato gene expression. Pp. 122 in Henneberry, T.J., R.M. Faust, W.A. Jones, and T.M. Perring (eds.) Silverleaf whitefly: National research, action, and technology transfer plan, Third annual review of the second 5-year plan. USDA July 2000. 200 pp.
  • Brown, J.K., Perring, T.M., Cooper, A.D., Bedford, I.D., AND Markham, P.G. 2000. Genetic analysis of Bemisia (Homoptera: Aleyrodidae) populations by isoelectric focusing electrophoresis. Biochemical Genetics 38: 13-25.
  • Vav De Ven, W.T.G, Levesque, C.S., Perring, T.M., Walling, L.L. 2000. Local and systemic changes in squash gene expression in response to silverleaf whitefly feeding. Plant Cell 12: 1409-1424.
  • Henneberry, T.J., Faust, R.M. , Jones, W.A., and Perring, T.M. (eds.). 2000. Silverleaf whitefly: National research, action, and technology transfer plan: Third annual review of the second 5-year plan. 200 pp.
  • Van De Ven, W.T.G., Levesque, C.S., Perring, T.M., and Walling, L.L. 2000. Characterization of two squash genes induced by silverleaf whitefly infestaion. Pp. 120 in Henneberry, T.J., R.M. Faust, W.A. Jones, and T.M. Perring (eds.) Silverleaf whitefly: National research, action, and technology transfer plan, Third annual review of the second 5-year plan. USDA July 2000. 200 pp.


Progress 01/01/99 to 12/31/99

Outputs
Studies have continued on the biology of BEMISIA ARGENTIFOLII and its natural enemies. We have shown that variation in host plants contribute to differential foraging behavior of ERETMOCERUS EREMICUS, a whitefly parasitoid. This causes profound differences in the intrinsic rate of increase of this parasitoid. Glandular leaf trichomes of ABUTILON THEOPHRASTI were shown to hinder the searching ability of E. EREMICUS and in some cases the parasitoids are trapped in the plant exudates where they die. Research suggests that this plant may provide whiteflies with enemy free space. Other work has shown that whiteflies and their parasitoids can be stored for short periods of time at cold temperatures. This will facilitate preparing and holding parasitoids in anticipation for sending to other countries. Isoelectric focusing studies have revealed 3 distinct groups of whiteflies originally classified as BEMISIA TABACI. These groups are B. TABACI, Type A of western hemisphere origin, B. ARGENTIFOLII (B. TABACI, Type B) from the eastern hemisphere, and a single population from a specific plant species in Africa. Evidence continues to grow suggesting B. TABACI consists of several or many species. Molecular studies have identified several novel genes in tomato and squash that are unique to feeding by B. ARGENTIFOLII. Work to characterize these genes is continuing. In research on OLIGONYCHUS PRATENSIS, a tetranychid pest on dates, we have demonstrated differential levels of sulfur resistance in mites collected from different areas of the date growing region. While spider mites are resistant, predatory mites are highly susceptible. We also have identified two predatory mites species, GALENDROMUS MCGREGORI and NEOSEIULUS COMITATUS in the date system which show promise for control of the date mites. These two mites are being evaluated for spider mite control in lab and field studies.

Impacts
Research is aimed at revealing information of pest whiteflies and mites, and their natural enemies. This past year, the lab focused on a whitefly species that vectors several plant viruses, and a mite species that is a direct pest of dates. The primary method of managing these pests is to use chemical pesticides. Our hope is manipulate natural enemies to become part of a more comprehensive integrated pest management program.

Publications

  • Puthoff, D.P., Perring, T.M. and Walling, L.L. 1999. Plant-insect interactions: The defense reaction of tomato to whitefly feeding. Pp. 107 in Henneberry, T.J. and R.M. Faust (eds.) 1999 Silverleaf whitefly: National research, action, and technology transfer plan, 1997-2001: Second annual review of the second 5-year plan. USDA 1999-01. 195 pp.
  • Van de Ven, W.T.G., Perring, T.M. and Walling, L.L. 1999. Genes modulated in silverleaf whitefly infected squash. Pp. 108 in Henneberry, T.J. and R.M. Faust (eds.) 1999 Silverleaf whitefly: National research, action, and technology transfer plan, 1997-2001: Second annual review of the second 5-year plan. USDA 1999-01. 195 pp.
  • Headrick, D.H., Bellows, T.S. and Perring, T.M. 1999. Development and reproduction of a population of ERETMOCERUS EREMICUS (Hymenoptera: Aphelinidae) on BEMISIA ARGENTIFOLII (Homoptera: Aleyrodidae). Environ. Entomol. 28: 300-306.
  • Lacey, L.A., Millar, L., Kirk, A.A., and Perring, T.M. 1999. Effect of storage temperature and duration on the survival of eggs and nymphs of BEMISIA ARGENTIFOLII (Homoptera: Aleyrodidae) and pupae of the whitefly parasitoid ENCARSIA FORMOSA (Hymenoptera: Aphelinidae). Ann. Entomol. Soc. Am. 92: 430-434.
  • Gruenhagen, N.M. and Perring, T.M. 1999. Velvetleaf: A plant with adverse impacts on insect natural enemies. Environ. Entomol. 28: 884-889.
  • Perring, T.M., Gruenhagen, N.M, and Farrar, C.A. 1999. Management of plant viral diseases through chemical control of insect vectors. Ann. Rev. Entomol. 44: 457-481.
  • Perring, T.M., Brown, J., Cooper, A.D., Bedford, I. and Markham, P. 1999. Genetic analysis of BEMISIA (Homoptera: Aleyrodidae) populations by isoelectric focusing electrophoresis. Pg. 19 in Henneberry, T.J. and R.M. Faust (eds.) 1999 Silverleaf whitefly: National research, action, and technology transfer plan, 1997-2001: Second annual review of the second 5-year plan. USDA 1999-01. 195 pp.


Progress 01/01/98 to 12/01/98

Outputs
Studies have quantified the behavior of ERETMOCERUS sp. nr. CALIFORNICUS (now known as ERETMOCERUS EREMICUS) an important natural enemy of BEMISIA ARGENTIFOLII on various host plants. Walking and searching speeds were greater on cotton than on melon, which corresponds to differential parasitism observed on these plants in the field. Laboratory comparisons of searching behavior on these two hosts, sweet potato, and ABUTILON THEOPHRASTI indicated that the most important factor influencing parasitism was propensity of female parasites to alight and remain to search the hosts. Preconditioning had a tremendous impact on parasitism. Further studies comparing A. THEOPHRASTI and HETEROTHECA GRANDIFLORA showed a wide differential between the propensity of parasites to search these two plants. The glandular trichomes of A. THEOPHRASTI trapped parasites resulting in relatively little parasitism of whiteflies on this leaf. This has lead to a hypothesis that this plant may provide enemy free space for whiteflies. Research has investigated the impact of B. ARGENTIFOLII feeding on tomato irregular ripening (TIR). Preliminary results indicate that whitefly density and distance from developing fruit are crucial parameters in the determination of TIR. While the "signal" which results in TIR is not understood, studies have indicated that the critical time of induction for TIR is prior to or during flower development. Studies have continued the characterization of peach mosaic virus, a pathogen vectored by the eriophyid mite ERIOPHYES INSIDIOSUS.

Impacts
(N/A)

Publications

  • HEADRICK, D. H., BELLOWS JR, T.S., and PERRING, T.M. 1996. Female Behaviors of ERETMOCERUS sp. nr. CALIFORNICUS (Hymenoptera: Aphelinidae) attacking BEMISIA ARGENTIFOLII (Homoptera: Aleyrodidae) on Cotton, GOSSYPIUM HIRSUTUM, (Malvaceae).
  • HEADRICK, D.H., BELLOWS, JR, T.S., and PERRING, T.M. 1996. Host-plant effects on the behavior of ERETMOCERUS sp. nr. CALIFORNICUS females raised from melon.. Entomophaga 41: 15-26.
  • HEADRICK, D. H., BELLOWS JR, T. S., and PERRING, T. M. 1997. Behavior of ERETMOCERUS sp. nr. CALIFORNICUS females attacking BEMISIA ARGENTIFOLII on two native California weeds. Canadian Entomologist
  • GISPERT, C., PERRING, T.M., and CREAMER, R. 1998. Purification and characterization of peach mosaic virus. Plant Dis. 82: 905-908.
  • GISPERT, C., OLDFIELD, G.N., PERRING, T.M., and CREAMER, R. Biology of the transmission of peach mosaic virus by ERIOPHYES INSIDIOSUS (Acari: Eriophyidae). Plant Dis. 82: 1371-1374.
  • PERRING, T.M. 1997. Technology transfer for the USDA 5-year national research and action plan (1992-1996). Pp. 8-39 in Henneberry, T. J., N.C. Toscano, T.M. Perring, and R.M. Faust (eds.). Silverleaf whitefly. 1997 supplement to the five-.
  • PERRING, T.M. and FARRAR, C.A. 1998. Sampling protocol for silverleaf whitefly on tomato. Pg. 21 in Henneberry, T.J., N.C. Toscano, T.M. Perring, and R.M. Faust (eds.). 1997. Silverleaf whitefly: National research, action and technology.


Progress 01/01/97 to 12/01/97

Outputs
Studies have shown that silverleaf whitefly (SLWF), BEMISIA ARGENTIFOLII, adult density counted in tomato leaf turns is a good predictor of 3rd and 4th instar nymph numbers on the fourth node from the terminal leaf. This provides a grower-friendly tool for assessing the number of whiteflies on tomato, which can be related to the amount of tomato irregular ripening. In related studies, we have completed the release of ENCARSIA LUTEA in the Imperial Valley, thus concluding a three-year rearing and release program of 3 exotic parasites. Other work has continued to characterize genes unique to plants on which SLWF has fed. We have shown that watermelon mosaic virus 2 is the most prevalent virus in cantaloupe growing regions of the San Joaquin Valley. Surveys indicated that zucchini yellow mosaic virus is increasing in the area. This work suggests that management strategies for viruses will be specific to each growing region of the Valley. We have developed a rearing method for ERIOPHYES INSIDIOSUS, a fastidious bud mite that vectors peach mosaic virus. We also have characterized this virus to have long flexuous filamentous rod-shaped particles with an average size of 888nm. RNA extracted was 8.1 kb in size and the capsid protein was 27kDa. These parameters suggest that this virus is in the trichovirus group. Transmission efficiency by the mite can be as high as 17% by single mite transfers. The mite can transmit virus with a minimum acquisition access period of 3 days, a minimum inoculation access period between 3 and 6 hr., and no latent period.

Impacts
(N/A)

Publications

  • PERRING, T.M. 1997. Technology transfer for the USDA 5-year national research and action plan (1992-1996). Pp. 8-39 in Henneberry, T. J., N.C. Toscano, T.M. Perring, and R.M. Faust (eds.). Silverleaf whitefly. 1997 supplement to the five-.
  • PERRING, T.M. and GRUENHAGEN, N.M. 1997. Velvetleaf: a possible candidate for enemy free space in desert agricultural systems. Pp. 74 in Henneberry, T. J., N.C. Toscano, T.M. Perring, and R.M. Faust (eds.). 1997. Silverleaf whitefly. 1997.
  • GRAFTON-CARDWELL, E.E., PERRING, T. M., SMITH, R.., VALENCIA, J. and FARRAR, C.A. 1996. Occurrence of mosaic viruses in melons in the central valley of California. Plant Dis. 80: 1092-1097.
  • GISPERT, C., PERRING, T.M., and OLDFIELD, G.N. 1997. Rearing Eriophyes insidiousus Keifer and Wilson (Acari: Eriophyiodea), a fastidious bud mite. Internat. J. Acarol. 24: 227-231.
  • LEVESQUE, C.S., PERRING, T.M. and WALLING, L. L. 1997. Differential gene expression: a comparison of the silverleaf whitefly and sweetpotato whitefly using differential RNA display. Pp. 93 in Henneberry, T. J., N.C. Toscano, T.M. Perring,.
  • HEADRICK, D., BELLOWS, T., PERRING, T. and ORR, B. 1997. Natural enemy releases against the silverleaf whitefly in the Imperial Valley. Pp. 145 in Henneberry, T. J., N.C. Toscano, T.M. Perring, and R.M. Faust (eds.). 1997. Silverleaf white.


Progress 01/01/96 to 12/30/96

Outputs
This research program was established to develop information which will lead to effective management of arthropod-vectored pathogens. We have elucidated the epidemiology of cucurbit viruses and determined that growers can reduce the spread of aphid-borne zucchini yellow mosaic potyvirus (ZYMV) through early season monitoring and removal of overwintering virus source plants. In the lower desert, where this problem exists, the only such plants are in the Cucurbitaceae. Isolation from native cucurbits in the natural desert ecosystem and cultivated squashes in home gardens also can reduce primary spread of virus into the agricultural ecosystem. Research also has shown that using a mild strain of ZYMV can be applied using standard agricultural sprayers, and provide protection against the yield-limiting strain present in southern California. In a second viral pathosystem, we determined that severe lettuce infectious yellows virus (LIYV) problems in lettuce were related to the numbers of BEMISIA TABACI migrating from summer-grown cotton. Whiteflies moved into fall-planted cantaloupe fields where they further multiplied and acquired virus, after which they infected fall-planted lettuce. Research also identified a whit-efly species shift from B. TABACI to BEMISIA ARGENTIFOLII. We described this new species, and documented that its arrival in the southwest desert was accompanied by a dramatic shift in the incidence of LIYV. We have conducted biological studies on this new pest species and its natural enemies.

Impacts
(N/A)

Publications

  • PERRING, T. M. and CHANDLER, L. D. 1995. Damage caused by arthropods - Mites, aphids, leafminers, thrips and whiteflies. Pp 67-71 in Compendium of Cucurbit Diseases (T.A. Zitter, D.L. Hopkins and C.E. Thomas eds.). American Phytopathologic.
  • HEADRICK, D. H., BELLOWS, JR, T. S. and PERRING, T. M. 1995. Behaviors of femaleERETMOCERUS sp. nr. CALIFORNICUS (Hymenoptera: Aphelinidae) attacking BEMISIA ARGENTIFOLII (Homoptera: Aleyrodidae) on sweet potato. Environ. Entomol. 24: 412.
  • PERRING, T. M., FARRAR, C. A., BLUA, M. J., WANG, H. L. and GONSALVES, D. 1995. Cross protection of cantaloupe with a mild strain of zucchini yellow mosaic virus: Effectiveness and application. Crop Protection 14: 601-606.
  • PERRING, T.M. 1996. Biological differences of two species of BEMISIA that contribute to adaptive advantage. Pp. 3-16 in D. Gerling and D. Mayer (eds.) BEMISIA 1995: Taxonomy, biology, damage, control, and management. Intercept, Andover,.
  • HEADRICK, D. H., BELLOWS, JR, T. S., and PERRING, T. M. 1996. Female behaviors of ERETMOCERUS sp. nr. CALIFORNICUS (Hymenoptera: Aphelinidae) attacking BEMISIAARGENTIFOLII (Homoptera: Aleyrodidae) on cotton, GOSSYPIUM HIRSUTUM,.


Progress 01/01/95 to 12/30/95

Outputs
Research to develop a sampling program for silverleaf whitefly (SLWF), BEMISIA ARGENTIFOLII on tomato has found a good correlation between adult numbers counted on terminal tomato leaflets and numbers of eggs. The next step in these studies is to follow immature development as a function of leaf age, so that action thresholds for tomato irregular ripening (TIR) can be developed. Studies of SLWF parasite behavior have continued on various whitefly-host plants. This work has suggested that one of the weeds, velvetleaf, a plant common in southern California agricultural regions, may be characterized as enemy free space for SLWF. other studies have shown higher percentage parasitism in cotton growing adjacent to camphor weed intercropped in the field. Percentage parasitism declined with distance from the camphor weed. We also have completed a full season of releasing a new parasite species, AMITUS BENNETTI into Imperial County, CA. After releasing over 380,000, we find few adults in the area, suggesting limited establishment. Currently we are rearing and releasing ENCARSIA LUTEA. We have completed our second year of research on the epidemiology of greenhouse whitefly (GHWF) vectored tomato infectious chlorosis virus. Movement of this virus is determined largely by movement of the whitefly, which appears to be limited in the coastal regions of southern California.

Impacts
(N/A)

Publications

  • BERGH, J.C., PERRING, T.M. and LEBLANC, J-P.R. 1995. Identification of silverleaf whitefly BEMISIA ARGENTIFOLII Bellows and Perring (Homoptera: Aleyrodidae), in Nova Scotia greenhouses. Can. Entomol. 127: 141-142.
  • OLDFIELD, G.N., CREAMER, R., GISPERT, C., OSORIO, F. RODRIGUEZ, R. and PERRING, T.M. 1995. Incidence and distribution of peach mosaic and its vector, ERIOPHYES INSIDIOSUS (Acari: Eriophyidae) in Mexico. Plant Dis. 79: 186-189.
  • NUESSLY, G.S. and PERRING, T.M. 1995. Influence of endosulfan on BEMISIA TABACI (Homoptera: Aleyrodidae) populations, parasitism, and lettuce infectious yellows virus in late-summer planted cantaloupe. J. Entomol. Sci. 30: 49-61.


Progress 01/01/94 to 12/30/94

Outputs
We have continued surveys of silverleaf whitefly (SLWF), BEMISIA ARGENTIFOLII, on crops and weeds in California. Densities in the south were higher than they have been in the past 4 years and whiteflies continue to increase in central California. This year, we documented a substantial increase in the amount of tomato irregular ripening (TIR), a disorder related to SLWF feeding, in the field. TIR severity was correlated with whitefly density. In TIR fruit, we have documented reduced levels of E8 and PG1 transcript. We have seen reduced levels of wound-induced LAP mRNA in leaves located close to feeding SLWF. We have studied SLWF parasite behavior on glabrous and hirsute melon isolines, finding a higher percentage of ovipositional success on the glabrous line. we also investigated the use of camphorweed as a weed reservoir for SLWF parasites. We have completed our first year of research on greenhouse whitefly (GHWF), TRIALEURODES VAPORARIORUM, vectored tomato infectious chlorosis virus of tomato. Of 70 plants sampled, 15 served as excellent hosts for GHWF. Parasitism rates varied on these plants. Very little virus incidence was found in the study area. In preliminary studies, tomato yield was negatively impacted by virus infection.

Impacts
(N/A)

Publications

  • BELLOWS, T.S., JR., PERRING, T.M., GILL, R.J. and HEADRICK, D.H. 1994. Description of a species of BEMISIA (Homoptera: Aleyrodidae). Ann. Entomol. Soc. Am. 87: 195-206.
  • WALKER, G.P. and PERRING, T.M. 1994. Feeding and oviposition behavior of whiteflies (Homoptera: Aleyrodidae): Interpretation of AC electronic feeding monitor waveforms. Ann. Entomol. Soc. Am. 87: 363-374.
  • BLUA, M.J., PERRING, T.M. and MADORE, M.A. 1994. Temporal changes in amine nitrogen and carbohydrates in CUCURBITA PEPO infected with zucchini yellow mosaic virus. J. Chemical Ecology 20: 691-707.
  • BLUA, M.J., PERRING, T.M., NUESSLY, G.S., DUFFUS, J.E. and TOSCANO, N.C. 1994. Seasonal cropping pattern effects on abundance of BEMISIA TABACI (Homoptera: Aleyrodidae) and the incidence of lettuce infectious yellows virus. Environ.
  • PERRING, T.M., FARRAR, C.A., BLUA, M.J., WANG, H.L. and GONSALVES, D. 1994. Cross protection of cantaloupe with a mild strain of zucchini yellow mosaic virus: Effectiveness and application technology. Crop Protection. In Press.
  • HEADRICK, D.H., BELLOWS, T.S., JR. and PERRING, T.M. 1994. Behaviors of female ERETMOCERUS sp. nr. CALIFORNICUS (Hymenoptera: Aphelinidae) attacking BEMISIA ARGENTIFOLII (Homoptera: Aleyrodidae) on sweet potato, IPOMOEA BATATAS.


Progress 01/01/93 to 12/30/93

Outputs
We have found morphological differences between nymphs of sweetpotato whitefly, BEMISIA TABACI, and silverleaf whitefly, BEMISIA ARGENTIFOLII. Differences are found in the presence/absence of the fourth anterior submarginal setae and in the width of the tracheal fold. We have continued our field survey to described the temporal and spatial distribution of whiteflies and their parasites on crop and weed plants in the southern desert and central valley regions of California. We have reproduced tomato irregular ripening and found that the severity of this physiological disorder caused by silverleaf whitefly feeding is related to whitefly density. We have identified PCR primers which amplify aphid and whitefly DNA, and we are using these to provide markers for distinguishing between host races of these polyphagous insects. We have begun studies on the epidemiology of a new tomato virus which is vectored by the greenhouse whitefly, TRIALEURODES VAPORARIORUM.

Impacts
(N/A)

Publications

  • GRUENHAGEN, N.M., PERRING, T.M., BEZARK, L.G., DAOUD, D.M., and LEIGH, T.F. 1993. Silverleaf whitefly present in the San Joaquin Valley. Calif. Agric. 47(1): 4-6.
  • REUTER, L.L., TOSCANO, N.C., and PERRING, T.M. 1993. Modification of MYZUS PERSICAE (Sulzer) (Homoptera: Aphididae) feeding behavior by selected compounds. Environ. Entomol. 22: 915-919.
  • PERRING, T.M., FARRAR, C.A., BELLOWS, T.S., COOPER, A.D., and RODRIGUEZ, R.J. 1993. Evidence for a new species of whitefly: UCR findings and implications. Calif. Agric. 47(1): 7-8.
  • PERRING, T.M. and FARRAR, C.A. 1993. Stimulation of growth and yield of virus-infected cantaloupe with pyrethroids. Plant Dis. 77: 1077-1080.
  • ROYALTY, R.N., FARRAR, C.A., and PERRING, T.M. 1993. Taxonomic guide to the alate aphids of inland valley and Colorado desert agriculture of southern California. Southwest Entomol. Suppl. #17, 25 pp.
  • PERRING, T.M., FARRAR, C.A., COOPER, A.D., BELLOWS, T.S. JR., and RODRIGUEZ, R.J. 1993. Determining whitefly species: Response. Science 261: 1333-335.
  • PERRING, T.M., COOPER, A.D., RODRIGUEZ, R.J., FARRAR, C.A., and BELLOWS, T.S. 1993. Identification of a whitefly species by genomic and behavioral studies. Science 259: 74-77.


Progress 01/01/92 to 12/30/92

Outputs
We have shown that the whitefly introduced into southern California in 1990, which originally was identified as a strain of BEMISIA TABACI, is a distinct species. Results are based on the lack of gamete transfer in crossing experiments, no copulation in mating compatibility studies, distinct allozymic differences, and differences in randomly amplified DNA products. We refer to this new species as the silverleaf whitefly. We have developed techniques for electronic monitoring of whitefly feeding behavior, which are being used to elucidate plant stimuli important in host selection. We have described the temporal and spatial distribution of whiteflies and their parasitoids on crop and weed plants in the desert agroecosystem. Other studies on the mechanisms of plant physiological disorders caused by silverleaf whitefly feeding are under way. In aphid-borne virus research, we have investigated the mechanisms involved when attempting to use intercropping as a management strategy.

Impacts
(N/A)

Publications

  • CASTLE, S.J., PERRING, T.M., FARRAR, C.A. and KISHABA, A.N. 1992. Field and laboratory transmission of watermelon mosaic virus 2 and zucchini yellow mosaic virus by various aphid species. Phytopathology 83:235-240.
  • PRABHAKER, N., TOSCANO, N.C., PERRING, T.M., NUESSLY, G., KIDO, K. and YOUNGMAN, R.R. 1992. Resistance monitoring of sweetpotato whitefly (Homoptera: Aleyrodidae) in the Imperial Valley of California. J. Econ. Entomol. 85:1063-1068.
  • PERRING, T.M., COOPER, A. and KAZMER, D.J. 1992. Identification of the poinsettia strain of BEMISIA TABACI (Homoptera: Aleyrodidae) on broccoli by electrophoresis. J. Econ. Entomol. 85:1278-1284.
  • BLUA, M.J. and PERRING, T.M. 1992. Alatae production and population increase of aphid vectors on virus-infected host plants. Oecologia 92:65-70.


Progress 01/01/91 to 12/30/91

Outputs
Studies on aphid-vectored viruses have resulted in a disease management program based on eliminating-zucchini yellow mosaic virus (ZYMV) source plants prior to melon emergence. In 1991 limited numbers of source plants were located; however, when these were not removed, surrounding melon fields became severely infected with ZYMV. Areas where sources were removed remained clean. An extended cool spring allowed prolonged aphid activity and this resulted in severe infection in late-planted fields. Research showed the benefit of using a mild-strain of ZYMV for cross-protection of cantaloupe. We also developed methodologies for inoculating plants in large-scale, direct-seeded agriculture using standard agricultural spray equipment. An introduction of a new strain of BEMISIA TABACI into California resulted in unprecedented damage to fall vegetables. We developed electrophoetic techniques for distinguishing this new strain from the old and are in the process of genetic experiments to determine the degree of relatedness between the two strains. Other studies into the biology and biological control of this new strain are underway.

Impacts
(N/A)

Publications