Source: OREGON STATE UNIVERSITY submitted to
PREDATORS OF THE HEMLOCK WOOLLY ADLEGID IN THE PACIFIC NORTHWEST
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0206985
Grant No.
(N/A)
Project No.
OREZ-FS-820-P
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Jul 1, 2006
Project End Date
Dec 30, 2011
Grant Year
(N/A)
Project Director
Ross, D. W.
Recipient Organization
OREGON STATE UNIVERSITY
(N/A)
CORVALLIS,OR 97331
Performing Department
FOREST ECOSYSTEMS AND SOCIETY
Non Technical Summary
The hemlock woolly adelgid, an introduced insect, is threatening the survival of the highly susceptible eastern and Carolina hemlocks in forests throughout the eastern United States. Biological control with natural enemies is considered to be one of the only options for managing this insect in forests. This study will identify predators associated with the hemlock woolly adelgid in the Pacific Northwest that could potentially be used in biological control programs in the East.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2113110113010%
2150612113020%
2153110113070%
Goals / Objectives
The goal of this project is to understand the role of predators in the population dynamics of the hemlock woolly adelgid (HWA) and balsam woolly adelgid (BWA) in the Pacific Northwest. Specific objectives are: 1. Identify the suite of predators associated with HWA in Oregon and Washington. 2. Determine the relationships between abundance of predator species, density of HWA populations, and environmental variables. 3. Describe the phenological relationships among predator species and HWA. 4. Identify the suite of predators associated with the balsam woolly adelgid (BWA) in Oregon.
Project Methods
One hundred and thirteen hemlock woolly adelgid-infested western hemlock trees in northwestern Oregon and western Washington will be sampled monthly. Trees will be sampled by beating branches over a tub and collecting dislodged predators. All predators will be returned to the laboratory to be identified and counted. Trees with no apparent HWA infestation will be sampled as controls at seven seed orchards; non-infested trees are not available at the remaining 10 sites. The number of control trees sampled will be approximately equal to 25% of the total infested trees sampled at each orchard. Latitude, longitude, elevation, average monthly precipitation, and average monthly temperature will be recorded for each site. Average monthly precipitation and temperature data will be obtained from nearby weather stations. Height and diameter at breast height will be recorded for each tree. The following data will be recorded at each visit: date, time, temperature, weather conditions, state of defoliation, developmental stages of HWA, and a population score of HWA woolly masses in the sample area. All 0.16 m2 samples will be assigned an adelgid infestation score at each visit based on the number of ovisacs visible in the sample area using the following categories: 0 = no ovisacs present, 1 = 1 to 25 ovisacs, 2 = 26-100 ovisacs, 3 = more than 100 ovisacs. Similar scales are highly correlated with actual aphid population counts in agricultural settings. Infestation scores will not be recorded during four months of A. tsugae sistens aestival diapause when ovisac number will not be an accurate estimation of population density. Regression and correlation analysis will be used to evaluate relationships of prey and predator density to both biotic variables (prey/predator density and tree health) and abiotic variables (latitude, elevation, precipitation, and temperature). Depending on the diversity of predator taxa found across the study area, correlations of species richness to geographical gradients may be examined. Abundance of the most common predators and life stages of HWA will be graphed over time to determine synchronicity of predator and prey populations. Predatory insects associated with the balsam woolly adelgid (BWA), Adelges piceae Ratzeburg, infestations of firs, Abies sp., located in the Willamette Valley and Cascade Range in Oregon will be sampled annually from June through September during oviposition and crawler dispersal. Samples will be collected monthly from fifteen trees located across three sites. Sampling methods will include scanning for predators using an illuminated hand lens and funnel traps, both methods described by Harris and Dawson (1979). Pupating insects collected in funnel traps or by scrapping the bole will be reared to the adult stage in individual 1 cm2 cages as described above.

Progress 07/01/06 to 12/30/11

Outputs
OUTPUTS: The objective of this project was to study the predators of the hemlock woolly adelgid in the Pacific Northwest as possible biological control agents for this insect in the eastern US. Studies completed during this project have made significant advances toward that goal. Two gradaute students completed MS degrees working on this project. An extensive survey of the predator communities on western hemlock infested with hemlock woolly adelgid was conducted in western Oregon and Washington. Laboratory feeding trials with two Leucopis spp. predators and several alternative adelgid prey species were completed. Laboratory olfactometer studies with adult L. nigrinus tested the response of this predator to adelgids alone, adelgid host trees (infested and uninfested), and other conifer species. Results from this project were reported in 6 presentations at national meetings, 7 presentations at regional meetings, and 3 seminars at universities. The following presentations were delivered in 2011: Grubin, S.M., K.F. Wallin, and D.W. Ross. 2011. Evaluating Leucopis species (Diptera: Chamaemyiidae) from the Pacific Northwest as potential biological control agents of the hemlock woolly adelgid. North American Forest Insect Work Conference, Portland, OR. Grubin, S.M., K.F. Wallin, and D.W. Ross. 2011. Evaluating Leucopis species (Diptera: Chamaemyiidae) from the Pacific Northwest as potential biological control agents of the hemlock woolly adelgid. 3rd Annual Student Research in Entomology Symposium, Oregon State University, Corvallis, OR. Grubin, S.M., K.F. Wallin, and D.W. Ross. 2011. Evaluating Leucopis species (Diptera: Chamaemyiidae) from the Pacific Northwest as potential biological control agents of the hemlock woolly adelgid. Entomological Society of America Annual Meeting, San Diego, CA. PARTICIPANTS: Drs. Darrell W. Ross, Oregon State University, and Kimberly F. Wallin, Rubenstein School of Environment and Natural Resources, University of Vermont, served as co-PIs. Sarah Grubin and Glenn Kohler, graduate students in Entomology and Forest Science, respectively, at Oregon State University, conducted the field surveys and laboratory feeding trials. TARGET AUDIENCES: Scientists, resource managers, and entomologists involved in the development and application of a biological control program for the hemlock woolly adelgid in the eastern US, and other adelgids throughout the world. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
A diverse community of predators including 55 species in 14 families was found associated with the adelgid. This was consistent with the recent discovery that the insect was native to the Pacific Northwest, not introduced from Asia as was previously believed. Three adelgid specific predators dominated the predator community and were frequently found in large numbers. They were Laricobius nigrinus (Derodontidae), Leucopis argenticollis, and Leucopis piniperda (as L. atrifacies) (Chamaemyiidae). The abundance of these three predators was positively correlated to abundance of the adelgid. A total of eight species of hymenopterous parasitoids were reared from pupae of predators of the adelgid in the laboratory including two Pachyneuron spp. (Pteromalidae) and a Melanips sp. (Figitidae) from Leucopis spp. puparia. Laboratory feeding trials with the two Leucopis spp. demonstrated that these insects have the ability to utilize a number of native host species within the Adelgidae, although they prefer hemlock woolly adegid. These results support continued study of the Leucopis spp. as biological control agents for the adelgid in the eastern US. Laboratory olfactometer studies with adult L. nigrinus indicated no response to the adelgid alone and differential responses to adelgid host species and other conifers. The results suggest that L. nigrinus uses adelgid host tree odors to locate potential prey. The results also indicated that the condition of laboratory reared predators and season of releases need to be considered for predator releases to be most effective.

Publications

  • Kohler, G.R. 2007. Predators associated with hemlock woolly adelgid (Hemiptera: Adelgidae) infested western hemlock in the Pacific Northwest. M.S. Thesis. Oregon State Univ., Corvallis, OR. 121 p.
  • Kohler, G.R., V.L. Stiefel, K.F. Wallin and D.W. Ross. 2008. Parasitoids reared from predators of hemlock woolly adelgid (Hemiptera: Adelgidae) and the hymenopterous parasitoid community on western hemlock in the Pacific Northwest. Environ. Entomol. 37(6):1477-1487.
  • Kohler, G.R., V.L. Stiefel, K.F. Wallin and D.W. Ross. 2008. Predators associated with the hemlock woolly adelgid (Hemiptera: Adelgidae) in the Pacific Northwest. Environ. Entomol. 37(2):494-504.
  • Grubin, S.M. 2011. Evaluating Leucopis species (Diptera: Chamaemyiidae) from the Pacific Northwest as potential biological control agents of the hemlock woolly adelgid (Hemiptera: Adelgidae). M.S. thesis, Oregon State University, Corvallis, OR.
  • Wallin, K.F., T.M. Latty, and D.W. Ross. 2011. Orientation behavior of the predator Laricobius nigrinus (Coleoptera: Derondontidae) to hemlock woolly adelgid and host tree odors in a multi-chambered olfactometer. Environ. Entomol. 40: 864-872.
  • Grubin, S.M., D.W. Ross, and K.F. Wallin. 2011. Prey suitability and phenology of Leucopis spp. (Diptera: Chamaemyiidae) associated with hemlock woolly adelgid (Hemiptera: Adeligidae) in the Pacific Northwest. Environ. Entomol. 40: (in press).


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

Outputs
OUTPUTS: One M.S. student, Sarah Grubin, conducted studies on the phenology of Leucopis spp. predators and the hemlock woolly adelgid, and suitability of alternative adelgid prey for Leucopis spp. predators. The following presentations were delivered to share results with target audiences: Grubin, S.M., K.F. Wallin, and D.W. Ross. 2010. Evaluating two Leucopis species (Diptera: Chamaemyiidae) as potential biological control agents of the hemlock woolly adelgid. 2nd Annual Student Research in Entomology Symposium, Oregon State University, Corvallis, OR. Ross, D.W., S.M. Grubin, G.R. Kohler, and K.F. Wallin. 2010. Evaluation of Leucopis species (Diptera: Chamaemyiidae) from the PNW as potential biological controls for the hemlock woolly adelgid. USDA Forest Service Fifth Symposium on Hemlock Woolly Adelgid in the Eastern United States, Asheville, NC. Wallin, K.F., D. Ott, S. Grubin, G. Kohler, and D.W. Ross. 2010. Ecology and behavior of hemlock woolly adegid (Adelges tsugae) predators from Pacific Northwest USA. Population Dynamics, Biological Control, and Integrated Management of Forest Insects Symposium, sponsored by IUFRO units 7.03.06, 7.03.07, and 7.03.13, Eberswalde, Germany, September 12-16, 2010. PARTICIPANTS: Drs. Darrell W. Ross, Oregon State University, and Kimberly F. Wallin, Rubenstein School of Environment and Natural Resources, Univerisity of Vermont, served as co-PIs. Sarah Grubin, M.S. student in Entomology at Oregon State University, conducted the laboratory feeding trials and field surveys. TARGET AUDIENCES: Scientists, resource managers, and entomologists involved in the development and application of a biological control program for the hemlock woolly adelgid in the eastern U.S., and other adelgids throughout the world. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Studies were conducted to determine the degree of host specificity of Leucopis spp. associated with Adelges tsugae in the Pacific Northwest by evaluating prey suitability and host acceptance in no-choice tests using four alernative adelgid prey species. While collecting immature Leucopis spp. to use in these tests, we identified a third species, Leucopis piniperda Malloch, associated with A. tsugae in Oregon and Washington. Leucopis spp. survival was highest on A. tsugae, but they were able to complete development on all four adelgid species. These results suggest that Leucopis spp. may have a conservative host range within the Adelgidae, but may not be specific to A. tsugae. Additionally, fourteen western hemlock trees infested with A. tsugae in Oregon and Washington were sampled over a period of 14 months to evaluate the seasonal abundance and synchrony of Leucopis spp. with A. tsugae in the field. Leucopis spp. larvae were collected year-round on branches infested with A. tsugae. There was a positive correlation between Leucopis spp. and A. tsugae abundance. Peak abundance of Leucopis spp. coincided with the presence of both progrediens and sistens eggs of A. tsugae in the field.

Publications

  • Wallin, K.F., T.M. Latty and D.W. Ross. 2011. Orientation of the predator Laricobius nigrinus Fender (Coleoptera: Derodontidae) to insect host and plant material in a multi-chambered olfactometer. Environ. Entomol. (In Press).


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

Outputs
OUTPUTS: One M.S. student, Sarah Grubin, conducted studies on the phenology of Leucopis spp. predators and the hemlock woolly adelgid, and suitability of alternative prey for Leucopis spp. predators. PARTICIPANTS: Drs. Darrell W. Ross, Oregon State University, and Kimberly F. Wallin, Rubenstein School of Environment and Natural Resources, Univerisity of Vermont, served as co-PIs. Sarah Grubin, M.S. student in Entomology at Oregon State University, conducted the laboratory feeding trials and field surveys. Richard Reardon and Brad Onken, USDA Forest Service, Forest Health Technology Enterprise Team, were cooperators and provided funding for the research. TARGET AUDIENCES: Scientists, resource managers, and entomologists involved in the development and application of a biological control program for the hemlock woolly adelgid in the eastern U.S. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
In no-choice laboratory feeding trials, twice as many field collected Leucopis spp. larvae survived feeding on hemlock woolly adelgid compared to those feeding on Pineus spp. These preliminary results suggest that hemlock woolly adelgid may be a preferred host over Pineus spp.

Publications

  • No publications reported this period


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

Outputs
OUTPUTS: One Ph.D. student, Glenn Kohler, conducted studies on the phenology of Leucopis spp. predators and the hemlock woolly adelgid, suitabilibity of alternative prey for Leucopis spp. predators, and conditions for rearing Leucopis spp. predators. The following presentations were delivered to share results with target audiences: Kohler, G.R., K.F. Wallin, and D.W. Ross (presenter). 2008. Evaluating chamaemyiid predators of HWA in the Pacific Northwest. USDA Forest Service Fourth Hemlock Woolly Adelgid Symposium, Hartford, CT. Kohler, G.R., K.F. Wallin, and D.W. Ross. 2008. Synchrony and host preferences of Leucopis spp. (Diptera: Chamaemyiidae), predators of the hemlock woolly adelgid in the Pacific Northwest. Western Forest Insect Work Conference, Boulder, CO. Wallin, K.F., G.R. Kohler, and D.W. Ross. 2008. Insights into hemlock woolly adelgid system in the Pacific Northwest provides hope for eastern hemlocks. Seminar, Plant and Soil Science Department, University of Vermont, Burlington, VT. Kohler, G.R., K.F. Wallin, and D.W. Ross (presenter). 2008. Synchrony and host preferences of Leucopis spp. (Diptera: Chamaemyiidae), predators of the hemlock woolly adelgid in the Pacific Northwest. Southern Forest Insect Work Conference, Chattanooga, TN. Wallin, K.F., T.M. Latty, and D.W. Ross. 2008. Behavioral responses of Laricobius nigrinus Fender (Coleoptera: Derodontidae) to chemosensory cues associated with plant material. Southern Forest Insect Work Conference, Chattanooga, TN. Wallin, K.F., Latty, T.M., and D.W. Ross. 2008. Orientation of the predator Laricobius nigrinus Fender (Coleptera: Derodontidae) to insect hosts and plant material in a multi-chambered olfactometer. Southern Forest Insect Work Conference. Chattanooga, TN. Wallin, K.F., T.M. Latty, and D.W. Ross. 2008. Orientation of the predator Lariciobius nigrinus Fender (Coleptera: Derodontidae) to insect hosts and plant material in a multi-chambered olfactometer. Entomological Society of America Annual Meeting, Reno, NV. PARTICIPANTS: Drs. Darrell W. Ross, Oregon State University, and Kimberly F. Wallin, Rubenstein School of Environment and Natural Resources, Univeristy of Vermont, served as co-PIs. Glenn Kohler, Ph.D. student at Oregon State University, conducted the laboratory and field studies. Dr. Melody Keena, USDA Forest Service, Northern Research Station was a cooperator and reared Leucopis on eastern hemlock woolly adelgid under quarantine conditions in Connecticut. Brad Onken, USDA Forest Service, Forest Health Technology Enterprise Team, was a cooperator and provided funding for the research. TARGET AUDIENCES: Scientists and practitioners involved in the development and application of a biological control program for the hemlock woolly adelgid in the eastern U.S. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
In laboratory choice experiments, field collected Leucopis spp. larvae demonstrated a preference for hemlock woolly adelgid over the alternative hosts, balsam woolly adelgid and Cooley spruce gall adelgid. Leucopis argenticollis was reared for one complete generation from adult to adult stages under artifical conditions in the laboratory on hemlock woolly adelgids. The F1 adults did not produce any eggs under the test conditions. Three parasitoid species of Leucopis spp. pupae were identified through rearing, an unidentified species of Melanips and two unidentified species of Pachyneuron. These preliminary results will be useful in evaluating the potential of Leucopis spp. predators as biological control agents for hemlock woolly aegid in the eastern U.S.

Publications

  • Kohler, G.R., V.L. Stiefel, K.F. Wallin and D.W. Ross. 2008. Parasitoids reared from predators of hemlock woolly adelgid (Hemiptera: Adelgidae) and the hymenopterous parasitoid community on western hemlock in the Pacific Northwest. Environ. Entomol. 37(6):1477-1487.
  • Kohler, G.R., V.L. Stiefel, K.F. Wallin and D.W. Ross. 2008. Predators associated with the hemlock woolly adelgid (Hemiptera: Adelgidae) in the Pacific Northwest. Environ. Entomol. 37(2):494-504.


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

Outputs
OUTPUTS: One M.S. student, Glenn Kohler, completed his thesis research and submitted a manuscript for publication in Environmental Entomology, a refereed journal. After completing his M.S. degree in March, Glenn began a Ph.D. program to study the biology and ecology of two Leucopis spp. predators that were identified in his M.S. work as potential biological control agents for hemlock woolly adelgid. The following presentations were delivered to share results with target audiences: Ross, D.W., G.R. Kohler and K.F. Wallin. 2007. Natural enemies of hemlock woolly adelgid in the Pacific Northwest. USDA Forest Service, HWA Biological Control Technical Committee Meeting, Annapolis, MD. Kohler, G.R., V.L. Stiefel, K.F. Wallin and D.W. Ross. 2007. Community structure and phenology of predators associated with the hemlock woolly adelgid (Hemiptera: Adelgidae) in the Pacific Northwest. Pacific Branch of the Entomological Society of America Annual Meeting, Portland, OR. Ross, D.W., G.R. Kohler and K.F. Wallin. 2007. Predator communities associated with hemlock woolly adelgid in the Pacific Northwest. Western Forest Insect Work Conference, Boise, ID. Ross, D.W. 2007. Top-down and bottom-up influences on hemlock woolly adelgid populations in the Pacific Northwest. Department of Entomology, North Carolina State University, Raleigh, NC. Kohler, G.R., V.L. Stiefel, K.F. Wallin and D.W. Ross. 2007. Field surveys for predators of the hemlock woolly adelgid (Hemiptera: Adelgidae) in the Pacific Northwest. California Forest Pest Council Annual Meeting, Woodland, CA. Kohler, G.R., K.F. Wallin and D.W. Ross. 2007. Life history and biology of two Leucopis species (Diptera: Chamaemyiidae), predators of the hemlock woolly adelgid in the Pacific Northwest. Entomological Society of America Annual Meeting, San Diego, CA. PARTICIPANTS: Dr. Darrell W. Ross (PI), Dr. Kimberly F. Wallin, Rubenstein School of Environment and Natural Resources, University of Vermont (co-PI), Dr. Melody Keena, USDA Forest Service, Northern Research Station (Cooperator). This project is funded, in part, through a cooperative agreement with the Northern Research Station. Mr. Brad Onken, USDA Forest Service, Forest Health Technology Enterprise Team (FHTET) (Cooperator). This project is funded, in part, through a coopertive agreement with the FHTET. Mr. Glenn Kohler (Graduate Student). Drs. Ross and Wallin are responsible for overall project supervision and planning. Glenn Kohler conducted field and laboratory work, analyzed data, and prepared research summaries. TARGET AUDIENCES: The target audience for this project includes forest entomology research scientists, forest entomologists with state and federal agencies, and natural resource managers throughout the range of eastern and Carolina hemlocks in eastern North America. Anyone with an interest in the impact of hemlock woolly adelgid on eastern and Carolina hemlocks should be interested in the outcomes of this project.

Impacts
Two species of predators in the family Chamaemyiidae, Leucopis argenticollis and Leucopis atrifacies, were found to be among the three most abundant and frequently encountered predators associated with hemlock woolly adelgid infested western hemlocks in the Pacific Northwest. Both species were reared on a diet of hemlock woolly adelgid in the laboratory. These results suggest that both species may be good candidates for biological control of hemlock woolly adelgid in eastern North America. The development of both Leucopis species in the field has been found to be closely synchronized with the development of the host adelgids. In no choice experiments in the laboratory, both Leucopis species larvae survived longer on hemlock woolly adelgid than on potential alternative hosts, balsam woolly adelgid and Cooley spruce gall adelgid.

Publications

  • Kohler, G.R. 2007. Predators associated with hemlock woolly adelgid (Hemiptera: Adelgidae) infested western hemlock in the Pacific Northwest. M.S. Thesis. Oregon State Univ., Corvallis, OR. 121 p.


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

Outputs
A field survey of predators associated with Adelges tsugae was completed in 2006. The predator community associated with A. tsugae infestations on 116 Tsuga heterophylla at 16 locations in Oregon and Washington were conducted every four to six weeks from March 2005 through November 2006. Predators collected from A. tsugae infested T. heterophylla represent 55 species in 14 families, listed in order of abundance: Derodontidae, Chamaemyiidae, Hemerobiidae, Coccinellidae, Cantharidae, Reduviidae, Miridae, Syrphidae, Chrysopidae, Coniopterygidae, Staphylinidae, Anthocoridae, Nabidae, and Raphidiidae. Laricobius nigrinus (Derodontidae), Leucopis argenticollis, and Leucopis atrifacies (Chamaemyiidae) are the dominant predators; together comprising 59% of predator specimens recovered. The abundance of derodontid larvae, L. nigrinus adults, chamaemyiid larvae, and L. argenticollis adults was predicted to increase with A. tsugae density. The remaining 52 species represent a diverse complex of predators potentially attacking A. tsugae; however, many are known to feed on non-adelgid prey. The phenology of immature and adult predators suggests temporal partitioning of prey across all seasons. Predators were most abundant when the two generations of A. tsugae eggs were present. Fifteen predator species were either reared from larvae to adult on a diet of A. tsugae in the laboratory or were observed feeding on A. tsugae.

Impacts
Two species of predatory flies in the family Chamaemyiidae were identified as common predators of Adelges tsugae in the field survey. These flies along with the the predatory beetle, Laricobius nigrinus, are the only host specific predators of A. tsugae that have been discovered in the Pacific Northwest. The beetle has already been evaluated for biological control in the East and has been approved for release. The flies represent additional potential biological control agents for A. tsugae in the eastern U.S. We plan to study these predators in more detail to determine whether they can be used safely and effectively as biological control agents in the East.

Publications

  • No publications reported this period