Source: WASHINGTON STATE UNIVERSITY submitted to
EFFECTS OF HERBICIDE APPLICATION TIMING AND TECHNIQUE ON BOHEMIAN KNOTWEED (POLYGONUM BOHEMICUM) SHOOT GROWTH AND RHIZOME VIABILITY
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0180936
Grant No.
(N/A)
Project No.
WNP00297
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Feb 1, 2006
Project End Date
Jan 31, 2010
Grant Year
(N/A)
Project Director
Miller, T. W.
Recipient Organization
WASHINGTON STATE UNIVERSITY
(N/A)
PULLMAN,WA 99164
Performing Department
MT. VERNON RESEARCH AND EXTENSION UNIT
Non Technical Summary
Invasive knotweeds currently dominate portions of many western Washington riparian areas. Adequate control of these knotweed species is a necessary for successful re-vegetation of salmon-bearing streams in western Washington with native woody species. Given that control of these knotweed species will require elimination of shoots arising from rhizomes, it is important to determine the effect of herbicides applied to foliage and/or stems on the viability of rhizome sections. Knowing whether application timing or technique is capable of suppressing knotweed rhizomal shoot production, and which combinations are most inhibitory to this function, will have critical importance to the design of successful control programs in the field.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2130330114010%
2132300114090%
Knowledge Area
213 - Weeds Affecting Plants;

Subject Of Investigation
0330 - Wetland and riparian systems; 2300 - Weeds;

Field Of Science
1140 - Weed science;
Goals / Objectives
Determine (1) the importance of Bohemian knotweed phenology and treatment technique on the effectiveness of treatment with glyphosate, imazapyr, and triclopyr, and (2) the effect of different glyphosate application techniques on shoot production from Bohemian knotweed rhizomes.
Project Methods
(1) Field studies. Stands of established Bohemian knotweed in western Washington will be selected for treatment with glyphosate, imazapyr, and triclopyr during the summer of 2006. Herbicides will be applied at the following rates: foliar, 5% glyphosate, 1.5% imazapyr, 2.5% triclopyr, and 2.5% glyphosate + 0.5% imazapyr; stem wipe, 33% solution for the three herbicides alone plus one glyphosate + imazapyr mixture. Early summer treatments will be made when the lower leaves of Bohemain knotweed shoots have fully expanded. Foliar treatments will be applied using a CO2-pressurized backpack sprayer. Stem wipe treatments will be made to rooted Bohemian knotweed stems cut at approximately 1 m above the soil and herbicide applied to the rooted stem within one hour of cutting using a sponge-tip paintbrush. Bohemian knotweed density (number of stems per plot) will be determined prior to each treatment during 2006. The stem height and diameter will also be measured at that time, and fresh and dry weight determined (leaves included). Effectiveness of control will be determined by counting knotweed stems in the spring and summer of 2007; stem height, diameter, and fresh and dry weight of those stems will also be determined. The experiment will be repeated in 2007-08. The experiment will be arranged in a completely random design with five replicates (10 treatment combinations x 4 herbicides = 40 treatments + 2 non-herbicide treatments = 42 total treatments per replicate). Plots will measure 5 by 5 m. (2). Greenhouse study. Bohemian knotweed crowns will be transplanted into large pots during the winter of 2006-07 and be allowed to establish during the spring of 2007. Shoots will be treated with glyphosate using one of three application methods: stem injection (100% product), foliar wipe (33% solution of product in water), or foliar overspray (1 to 5% product in water). Equivalent amounts of 100% product will be used for all application methods (e.g., 1 ml of glyphosate formulated as Aquamaster will be injected, 1 ml glyphosate will be mixed with 2 mls of water and wiped on the leaves, 1 ml glyphosate will be mixed with 95 mls of water and sprayed on the foliage). Herbicide will be allowed to translocate for 1, 8, 15, and 29 days after application. Knotweed plants will be removed from soil and 2.5-cm rhizome sections will be cut at 10-, 20-, and 30-cm distances away from the crown. Those sections will then be transplanted into fresh potting soil and maintained for 6 weeks; crowns and distal tips of rhizomes will also be included in the grow-out. Any shoots and roots present at the end of the 6-week grow-out will be counted, their length measured, presence of herbicide symptoms noted, and dry weight determined. The experimental design will be a randomized complete block with three replicates (1 herbicide (+ 1 non-treated) x 3 application methods x 4 translocation timings x 3 plants per sample = 37 plants per replicate, 111 plants total). Preliminary studies will be conducted during 2006; the experiment will be repeated in 2008.

Progress 02/01/06 to 01/31/10

Outputs
OUTPUTS: A symptomatic knotweed trial was established in 2008. Knotweed plants that had been treated with glyphosate or combination glyphosate + imazapyr by The Nature Conservancy every year for the last five years were further treated October 1, 2008 with broadcast applications of aminopyralid, glyphosate (Rodeo), imazapyr, triclopyr amine, aminopyralid + glyphosate, imazapyr + glyphosate, or triclpyr + glyphosate. These symptomatic knotweed plants were 15 to 20 cm tall and about 5% chlorotic at the time of treatment. The only treatments reducing knotweed shoot number at 8 months after treatment (MAT) were imazapyr alone or imazapyr + glyphosate, which reduced shoot number from 5.25 shoots in non-treated plots to 0.75 or 0 shoots/plot, respectively. By 12 MAT control with aminopyralid + glyphosate was significantly greater than with triclopyr (94 and 56%, respectively), although other treatments did not differ significantly from either extreme. While knotweed shoots treated with triclopyr or aminopyralid at 12 MAT were 34 and 25 cm respectively, similar to shoots from non-treated knotweed (32 cm). Knotweed shoot length resulting from the other treatments was less than on non-treated plants, ranging from 16 to 19 cm. Treatments were re-applied September 17, 2009 and resulting plant growth will be monitored during 2010. PARTICIPANTS: Two presentations were given to approximately 75 people who are actively managing invasive knotweed in Washington state. In addition, data on invasive knotweed management were presented to 150 participants at the annual meeting of the Alaska Committee for Noxious and Invasive Plant Management in Ketchikan, AK in October. TARGET AUDIENCES: State and Federal land managers, private land owners, weed control coordinators, and extension personnel. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Based on the results from these and other studies, recommendations for invasive knotweed control in the Pacific Northwest have been developed and are being applied in the field. Control of the species on treated sites routinely ranges from 85 to 100% from single applications of herbicide, giving many land managers hope that this species can now be effectively managed.

Publications

  • No publications reported this period


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

Outputs
OUTPUTS: Aminopyralid was applied at 0.5 and 1% Milestone, 0.5% Milestone with either 0.5% Garlon (triclopyr amine) or 1% Rodeo (glyphosate), or 0.75% Habitat (imazapyr). Applications were made to cut, bent, or intact giant knotweed (cut/bent July 26, treated August 31, 2007) or to cut or intact Bohemian knotweed (cut July 27, treated August 24, 2007). At one year after treatment, Bohemian knotweed control was 10 to 20% better by treating intact stems, regardless of treatment. Control from treatment of intact stems ranged from 89% with Habitat to 99 or 100% for the other treatments, compared to treatment of re-growth from cut stems (control was 56% for Habitat, 61% for Milestone + Garlon, 79% for Milestone + Rodeo, and 99 or 100% for Milestone at 0.5 and 1% (respectively). Giant knotweed control was generally enhanced by cutting and bending and then treating re-growth (about 10% improvement on average). Milestone effectiveness was particularly improved by cutting/bending, with 60 or 30% improvement at 0.5 and 1%, respectively. The opposite effect was seen with Habitat, with cutting/bending reducing control by 40 or 30%, respectively. PARTICIPANTS: The studies in this project have been conducted with involvement from noxious weed control coordinators, county extension faculty, state and federal agency land managers, homeowners, public utility personnel, Native American tribal leaders, and private environmental organizations. TARGET AUDIENCES: Noxious weed control coordinators, county extension faculty, state and federal agency land managers, homeowners, public utility personnel, Native American tribal leaders, and private environmental organization personnel have been updated as to preferred treatments to successfully manage invasive knotweed species. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
During 2008, four presentations were given to approximately 100 people who are actively managing invasive knotweed in Washington state. Based on the results from these and other studies, recommendations for invasive knotweed control in the Pacific Northwest have been developed and are now being applied in the field. Control of the weed on treated sites routinely ranges from 85 to 100% from single applications of herbicide, giving many land managers hope that this species can now be effectively managed. Following an additional year of study, this project will be complete.

Publications

  • No publications reported this period


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

Outputs
OUTPUTS: Results from my tests with foliar-applied glyphosate, triclopyr, and imazapyr on Bohemian, giant, and Himalayan knotweed transplants in the greenhouse indicate that triclopyr resulted in symptom expression, usually within 48 hours, and defoliation within two weeks. Plants treated with glyphosate and imazapyr did not show symptoms until about a week after treatment, and defoliation had only progressed to about 50% by three weeks. At three weeks after treatment, plants were clipped and knotweed re-growth was monitored for the next eight weeks. Relative susceptibility to these products did not differ much by species, although Bohemian transplants were most tolerant to herbicides applied at 0.5 to 1% product in water. It appears that imazapyr is the most active product on knotweed, as knotweed transplants did not re-grow when treated with imazapyr at 0.5% or greater, either applied alone or tank-mixed with glyphosate or triclopyr. Bohemian knotweed control 11 weeks after treatment with 1% glyphosate mix was 90% (compared to re-growth of untreated plants), while triclopyr at 1% gave 96% control. While knotweed in the field will likely require higher dosages of herbicide to achieve similar levels of control, it appears that all three of these herbicides alone or in combination will aid in the control of these species. TARGET AUDIENCES: Noxious weed coordinators, land management personnel, agency personnel, parks employees, landowners, non-profit organizations (such as The Nature Conservancy).

Impacts
It is still too early for impacts, although many local jurisdictions are using foliar applications of herbicides at these rates with good success.

Publications

  • No publications reported this period


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

Outputs
Testing of aminopyralid (Milestone, Dow AgroSciences) on Bohemian knotweed was completed in June, 2006. While there is activity of this herbicide on knotweed, dose rates that provide excellent control of certain other weed species were not effective on knotweed. Control from the 7 fl. oz product/acre rate provided only 33% control at 10 months after treatment (MAT). This contrasts unfavorably with 3% glyphosate (Aquamaster, Monsanto) or 0.75% imazapyr (Habitat, BASF) which gave 80% and 85% control at 10 MAT, respectively. In a second study conducted on Bohemian knotweed that had been mowed approximately one month prior to herbicide application, however, control with aminopyralid was improved, with the 7 fl.oz/acre rate resulting in 65% control at 10 MAT. This control was still inferior to glyphosate or imazapyr, however (96 and 99% control, respectively). Based on these data, a field trial was begun in which bending of knotweed stems is being tested for improved herbicide activity on Bohemian knotweed. Preliminary results indicate that bending enhanced initial knotweed control only about 7 percentage points (from 62 to 69% control at 1 MAT for non-bent and bent stems, respectively). Aminopyralid at 0.5, 1, and 1.5% gave about 75% control at 1 MAT, but when these rates were applied with 1.5% glyphosate, initial control improved to approximately 95%. At 1 MAT, 3% glyphosate gave about 48% control while 0.75% imazapyr control was about 28%. This trial will be continued into 2007 to determine knotweed control at 10 to 12 MAT.

Impacts
Ultimately, these studies will aid land owners and managers to better control noxious knotweed species. Previous studies on knotweed have helped to focus control efforts on certain foliar rates of glyphosate, imazapyr, and triclopyr, and helped to quantify potential for damage to other vegetation resulting from mid-summer injection of glyphosate into knotweed stems.

Publications

  • No publications reported this period


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

Outputs
Five riparian studies were conducted during 2005: (1) a greenhouse trial testing effects of glyphosate applied to Bohemian, Sakhalin, and Himalayan knotweeds on native salmonberry and thimbleberry, (2 and 3) field trials for controlling Bohemian and Sakhalin knotweed at two sites in western Washington, and (4 and 5) field trials testing effects of reed canarygrass control on establishment and growth of native broadleaf and conifer trees. In the greenhouse knotweed study, damage to knotweed from the overspray averaged 81% (98 to 100% control of Himalayan or giant, and 68% control of Bohemian), with berry plants sustaining 68% injury. Leaf wipes resulted in 89% knotweed control (83% Bohemian control and 98% of Himalayan and giant) and about 13% berry plant injury. Injection gave 88% knotweed control (88% of Bohemian and 100% of giant). While I was not able to inject Himalayan knotweed (stems too small), just the drop of glyphosate on the outside of the stem was enough to cause 63% injury of those plants. Thimble- and salmonberry injury from knotweed injection was 26%. Results from field tests with injection techniques on giant and Bohemian knotweed (2003-05) showed that 2.5 or 5 ml of glyphosate, triclopyr, and imazapyr gave 91 to 100% control of stems and crowns by eight weeks after treatment. I also tested wiping the lower three feet of knotweed stems with 33% herbicide solutions using a sponge paintbrush. Wiping uncut canes resulted in 63 to 80% stem control by eight weeks after treatment, while wiping canes whose tops had been cut off at a height of three feet resulted in 97 to 100% stem control. Knotweed control at one year after treatment was similar for all treatments, however. While knotweed "knockdown" was quicker if herbicides were applied at early flowering compared to post-flowering, there was no difference in control the following season. In the reed canarygrass trial, control in October of Year #1 was excellent with sequential applications of glyphosate or clethodim/imazapyr (94 and 90%, respectively), good with sethoxydim/sulfometuron (87%), and fair (70%) after three mowings. By April of Year #2, reed canarygrass control was holding with clethodim/imazapyr and sethoxydim/sulfometuron (93 and 91%, respectively), but control with glyphosate was beginning to slip (86%), and control had failed from mowing (48%). Tree height was reduced in October of Year #1 by clethodim/imazapyr and by mowing. New tree growth averaged 28 inches in plots treated with glyphosate, while growth was 8 inches shorter in plots treated with clethodim/imazapyr, and 5 and 7 inches shorter in plots treated with sethoxydim/sulfometuron or mowed, respectively. Clethodim/imazapyr reduced tree height an average of 11 and 5% in cottonwood and willow plots, respectively, compared to glyphosate-treated plots. Sethoxydim/sulfometuron also reduced average tree height in cottonwood plots by 12% compared to glyphosate-treated plots, but tree height in willow plots increased 8% when sethoxydim/sulfometuron was used. Tree height in cedar plots ranged from 23 to 26 inches among all treatments, without any clear trends in the data.

Impacts
Ultimately, these studies will aid land owners and managers to better control noxious riparian weeds such as Bohemian, Himalyan, and Sakhalin knotweed and reed canarygrass. Since these are perennial species, however, data at this point are too preliminary to draw many conclusions from these trials.

Publications

  • No publications reported this period


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

Outputs
Three knotweed studies were begun during 2004: a greenhouse trial testing glyphosate, triclopyr, imazapic, and imazapyr alone and in various combinations on Bohemian (Polygonum xbohemicum), Sakhalin (P. sachalinense), and Himalayan (P. polystachyum) knotweeds, and field trials for controlling Bohemian and Sakhalin knotweed at two sites in western Washington. Data from the greenhouse trial showed that foliar treatments including at least 0.5% formulated Garlon (triclopyr amine at 3 lb ae/gal) in water defoliated Himalayan knotweed 70 to 91% within two weeks, but Bohemian knotweed only 43 to 78%. Treatments with imazapyr, imazapic, and glyphosate never exceeded 75% defoliation for any species within three weeks. Control of Sakhalin and Bohemian knotweed seedlings was 90% or higher with all treatments except 0.5% glyphosate (Aquamaster at 5 lb ae/gal) in water 77 days after treatment. Bohemian knotweed transplants were the most difficult to kill, with control from 90 to 100% for most treatments, but only 80% control resulting from 0.5% formulated Aquamaster in water and 88% from the 1% rate. In field trials, second-year control of Bohemian and Sakhalin knotweed spring did not differ much by treatment, although crowns treated the year before were not effectively killed by wiping of the lower 3 feet of intact stems with glyphosate, triclopyr, or imazapyr (33% formulated product in water). Control of Bohemian knotweed at 8 weeks after treatment was 90 to 100% for triclopyr, or imazapyr wiped on stems cut to 3 feet tall (33% formulated product in water) or if 2.5 or 5 ml of formulated product was injected into internodal cavities. Glyphosate treatments were 98 and 94% control for 5 ml injections or cut/wipe treatment, while injection with 2.5 ml gave 84% control. Wiping uncut stems with 33% formulated product only resulted in 56 to 78% control, however. Sakhalin knotweed control exceeded 90% except for wipe treatments (63 to 80% control). In another study, reed canarygrass (Phalaris arundinacea) control in riparian areas and re-establishment of several native woody species was begun with initial glyphosate applications in summer, 2003. Native woody species (black cottonwood, Populus trichocarpa, Hooker willow, Salix hookeriana, and western red cedar, Thuja plicata) were transplanted in April, 2004. Reed canarygrass control in August after mowing, glyphosate, sethoxydim followed by sulfometuron, or clethodim followed by imazapyr during summer was 71, 94, 87, and 90%, respectively, while broadleaf weed control was 70, 84, 68, and 73%, respectively. Maintenance did not significantly affect tree survival or growth the first year. Initial survival of cottonwood and willow was 97%, while cedar survival was better when planted in cottonwood or cedar than when planted in willow (56, 50, and 31% survival, respectively).

Impacts
Ultimately, these studies will aid land owners and managers to better control noxious riparian weeds such as Bohemian, Himalyan, and Sakhalin knotweed and reed canarygrass. Since these are perennial species, however, data at this point are too preliminary to draw many conclusions from these trials.

Publications

  • No publications reported this period


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

Outputs
Three knotweed studies were begun during 2003: a greenhouse trial testing glyphosate, triclopyr, imazapic, and imazapyr alone and in various combinations, and field trials for controlling Japanese knotweed (Polygonum cuspidatum) and Sakhalin knotweed (P. sachalinense) at two sites in western Washington. Initial data from the greenhouse trial showed that foliar treatments including at least 0.5% formulated Garlon (triclopyr amine at 3 lb ae/gal) in water defoliated knotweed 68 to 94% within 7 days while imazapyr, imazapic, and glyphosate caused 25 to 85% defoliation within two weeks. Control of Sakhalin knotweed seedlings was 95% or higher with all treatments 78 days after treatment and 95 to 100% for Sakhalin knotweed transplants. Japanese knotweed transplants were the most difficult to kill, with control from 91 to 100% for most treatments, but only 77% control resulting from 0.5% formulated Roundup Pro (glyphosate at 4 lb ae/gal) in water. Initial control of Japanese and Sakhalin knotweed in the field trials was 91 to 100% for glyphosate, triclopyr, or imazapyr wiped on stems cut to 3 feet tall (33% formulated product in water) or if 2.5 or 5 ml of formulated product was injected into internodal cavities. Wiping uncut stems only resulted in 23 to 75% control, however. Field treatments will be evaluated for knotweed re-growth in spring, 2004, and all trials will be repeated in 2004. Testing on control of reed canarygrass (Phalaris arundinacea) in riparian areas and re-establishment of several native woody species was begun with initial glyphosate applications in summer, 2003. Native species will be transplanted in March, 2004, and maintenance treatments for reed canarygrass will be initiated.

Impacts
Ultimately, these studies will aid land owners and managers to better control noxious riparian weeds such as Japanese and Sakhalin knotweed and reed canarygrass. Since these are perennial species, however, data at this point are too preliminary to draw many conclusions from these trials.

Publications

  • No publications reported this period


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

Outputs
Conducted research trials of agricultural weeds in a variety of crops and western Washington noxious weeds (260 trials including over 4,900 individual treatments since 1997). Researched crops during 2002 include ornamental bulbs (tulip, daffodil, and iris), vegetable crops (cauliflower, sweet corn, potatoes, green peas, cucumbers, squash, and pumpkin), vegetable seed crops (spinach, beet, cabbage, coriander/cilantro, carrot, parsley, dill, and parsnip), small fruit (blueberries, strawberries, and raspberries) and in non-crop studies (meadow knapweed, reed canarygrass, blackberry, wild chervil, and general weed control).

Impacts
Results from trials conducted in minor crops, and/or my active support, contributed toward new and continuing Section 3 (federal label), Section 18 (emergency use label), and Section 24(c) (special local needs label) registrations for 28 herbicides in 20 western Washington crops.

Publications

  • Miller, T. 2002. Sandea and other weed control in cucumbers. Proceedings, Western Washington Horticultural Association, Seattle, WA, 2 p.
  • Miller, T. and C. Libbey. 2002. Weed management in vegetable seed crops: research results from 2001. Proceedings, Western Washington Horticultural Association, Seattle, WA, 9 p.
  • Miller, T., C. Libbey, and B. Maupin. 2002. Weed control in small fruit. Proceedings, 4th annual small fruit grower's workshop, WSU Vancouver, pp. 9-20.
  • Miller, T.W. 2002. Effects of diquat used as a pre-harvest desiccant on germination of spinach, beet, and coriander seed. HortScience 37:1032-1034.
  • Miller, T.W. 2002. Vegetative reproductive potential of Japanese knotweed (Polygonum cuspidatum). Weed Science Society of America, Reno, NV, WSSA Abstracts 42:61.
  • Miller, T.W. and B.G. Maupin. 2002. Canada thistle, yellow nutsedge, and quackgrass control in blueberries and raspberries. Proceedings, Western Society of Weed Science, Salt Lake City, UT, Vol. 55:10.
  • Miller, T.W. and C.R. Libbey. 2002. Sulfentrazone tolerance in selected potato cultivars. Western Society of Weed Science Research Progress Report, pp. 40-41.
  • Miller, T.W. and C.R. Libbey. 2002. Sweet corn tolerance to BAS 662 01H and dimethenamid-p. Western Society of Weed Science Research Progress Report, pp. 45-46.
  • Miller, T.W. and C.R. Libbey. 2002. Effects of herbicide application timing on field grown tulip, narcissus, and bulbous iris. Proceedings, Western Society of Weed Science, Salt Lake City, UT, Vol. 55:9.


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

Outputs
1. Weed interference in green pea. A reduced rate, combination treatment study, was conducted in 'Charo' green pea during 2001, in which weed control and yield parameters were measured. Peas treated with the full rates of Command + Basagran, full or half rate of Sencor (PRE), or full rate of Sencor (POST) provided excellent weed control and were top yielders (Table 1). Combinations of Command with Sencor (either PRE or POST) were also excellent. The half rate of Command was marginal in weed control and yield, as was the half rate of Sencor (POST). Sencor (PRE) with either Basagran or MCPA gave fairly good weed control, but fairly poor pea yield. Weed control was poor with Sencor (POST) + MCPA, but yield was fairly good. All other treatments failed in weed control and yields were correspondingly reduced. 2. Weed control in minor crops. Weed control methods evaluated in 2001 include mechanical (mowing, rototilling, flaming, etc.), chemical (both synthetic and organic compounds), and cultural (varietal competitiveness/sensitivity to herbicides). A total of 37 trials were conducted (including 1055 separate treatments) to determine the efficacy and crop safety of various treatment combinations and to screen new materials for potential usefulness.

Impacts
Due in part to data generated from extension research trials I conducted during 2001, the following were obtained for Washington State growers: (1) Section 24(c) registrations were secured for use of UpBeet in table beet and Swiss chard seed, Sandea in cucumber, Aim in raspberry, and Cobra in newly planted strawberry. (2) Section 18 registrations for Spartan in newly planted or dormant strawberries or during summer renovation. I also played an instrumental role in obtaining new/continuing Section 24(c) registrations for Strategy in cucumber, Betamix in table beet and Swiss chard seed, Nortron in spinach, table beet, and Swiss chard seed, Gallery and Karmex in daffodil and iris, Gramoxone Max in tulip, daffodil, and iris, Saber in blueberry, and Galigan in raspberry.

Publications

  • Miller, T. and C. Libbey. 2001. Weed control in green peas: 2000 trial results. Proceedings, Western Washington Horticultural Association, Seattle, WA.
  • Miller, T. and C. Libbey. 2001. Weed control in ornamental bulbs. Proceedings, Northwest Bulb and Cut Flower Conference, Seattle, WA, pp. 25-40.
  • Miller, T. and C. Libbey. 2001. Weed control in vegetable seed: a discussion session. Proceedings, Western Washington Horticultural Association, Seattle, WA.
  • Miller, T.W. and Al-Khatib, K. 2001. Interference between green pea, pale smartweed (Polygonum lapathifolium), and common lambsquarters (Chenopodium album). Weed Science Society of America, Greensboro, NC, WSSA Abstracts, 41:104-105.
  • Miller, T.W. and C.R. Libbey. 2001. Effects of field applications of nonselective, postemergence herbicides in ornamental bulbs. Proceedings, Western Society of Weed Science, Coeur d'Alene, ID, Vol. 54:5-6.
  • Miller, T.W. and C.R. Libbey. 2001. Herbicides for weed control in green pea. Western Society of Weed Science Research Progress Report, pp. 39-40.
  • Miller, T.W. and C.R. Libbey. 2001. Herbicides for weed control in spinach grown for seed. Western Society of Weed Science Research Progress Report, pp. 47-48.
  • Miller, T.W. and C.R. Libbey. 2001. Herbicides for weed control in table beets grown for seed. Western Society of Weed Science Research Progress Report, pp. 51-52.
  • Miller, T.W. and C.R. Libbey. 2001. Rotational crop response to several herbicides used in green pea. Proceedings, Western Society of Weed Science, Coeur d'Alene, ID, Vol. 54:44.


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

Outputs
1. Weed interference in green pea. In field trials, weeds were removed by hand from 'Charo' green pea at 1, 2, 3, 4, 5, or 6 weeks after emergence, and the pea production of these plots was compared to weedy and weed-free plots. Pea population and 50-pea weight were not severely reduced by weed competition, but pod number and pea yield were significantly reduced if weeds were not removed by 6 weeks after emergence. In greenhouse trials, green pea height and vegetative biomass was reduced by duration of competition with common lambsquarters (Chenopodium album) and pale smartweed (Polygonum lapathifolium), but pod number, pea leaf area, and reproductive biomass were not significantly changed. Smartweed reduced pea height, pod number, and both vegetative and reproductive biomass at a density of 2.5 plants per square foot, while lambsquarters did not reduce these pea parameters until a density of 5 plants per square foot was reached. Pea response to a combination of smartweed and lambsquarters was similar to that of common lambsquarters alone, indicating that smartweed is generally more competitive with green pea than is lambsquarters. 2. Weed control in minor crops. Weed control methods evaluated in 2000 include mechanical (mowing, rototilling, flaming, etc.), chemical (both synthetic and organic compounds), and cultural (varietal competitiveness/sensitivity to herbicides). A total of 38 trials were conducted (including 696 separate treatments) to determine the efficacy and crop safety of various treatment combinations and to screen new materials for potential usefulness.

Impacts
Section 24(c) registrations were secured for use of quizalofop in spinach, table beets, Swiss chard, and Chinese cabbage grown for seed due to data generated from extension research trials. Data was provided for the 2000 Section 18 registrations for oxyfluorfen in newly-planted strawberries and ryegrass grown for seed and triflusulfuron in table beet and Swiss chard seed crops.

Publications

  • No publications reported this period


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

Outputs
1. Weed interference in green pea. In field trials, weeds were removed by hand from 'Charo' green pea at 1, 2, 3, 4, 5, or 6 weeks after emergence, and the pea production of these plots was compared to weedy and weed-free plots. Preliminary analysis indicates that pea population and 50-pea weight were not severely reduced by weed competition, but that pod number and pea yield were significantly reduced if weeds were not removed by 6 weeks after emergence. In greenhouse trials, green pea height and vegetative biomass was reduced by duration of competition with common lambsquarters (Chenopodium album) and pale smartweed (Polygonum lapathifolium), but pod number, pea leaf area, and reproductive biomass were not significantly changed. Smartweed reduced pea height, pod number, and both vegetative and reproductive biomass at a density of 2.5 plants per square foot, while lambsquarters did not reduce these pea parameters until a density of 5 plants per square foot was reached. Pea response to a combination of smartweed and lambsquarters was similar to that of common lambsquarters alone, indicating that smartweed is generally more competitive with green pea than is lambsquarters. 2. Weed control in minor crops. Weed control methods evaluated in 1999 include mechanical (mowing, rototilling, flaming, etc.), chemical (both synthetic and organic compounds), cultural (varietal competitiveness/sensitivity to herbicides), and biological (Pseudomonas syringae pv. tagetis) control. A total of 39 trials were conducted (including 710 separate treatments) to determine the efficacy and crop safety of various treatment combinations (both synthetic and organic) and to screen new materials for potential usefulness. Crops included small fruit (strawberry, blueberry, and raspberry), ornamental bulbs (tulip, daffodil, and iris), vegetable seed (spinach, table beet, and cabbage), vegetable crops (green peas, cucumber, cauliflower, sweet corn, and potato), ryegrass grown for seed, and control of troublesome weed species (field horsetail, smooth hawkweed, and giant hogweed). During 1999, Section 18 and Section 24(c) registrations were secured for use of diquat in spinach, table beets, and coriander grown for seed due to data generated from extension research trials conducted at Washington State University Mount Vernon. Data was also provided for the 1999 Section 18 registrations for oxyfluorfen in newly-planted strawberries and ryegrass grown for seed.

Impacts
(N/A)

Publications

  • Miller, T. 1999. Weed control. In 1999 Pest Management Guide for Commercial Small Fruits, S. Roberts, ed. EB1491 (52 pp.).
  • Miller, T. and C. Libbey. 1999. Weed control in bulbs: research report and herbicide update. November 30, 1999. Northwest Bulb Growers Association, Seattle, WA.
  • Miller, T. 1999. Can we improve weed control?--1998 green pea research results. January 7, 1999. Western Washington Horticultural Association, Seattle, WA.
  • Miller, T. 1999. Less weeds, more seed: weed control trials in seed crops. January 6, 1999. Western Washington Horticultural Association, Seattle, WA.
  • Miller, T. 1999. Weed control, primocane suppression in small fruits--current research. January 7, 1999. Western Washington Horticultural Association, Seattle, WA.
  • Miller, T.W. and C.R. Libbey. 1999. Herbicides for weed control in green peas. Western Society of Weed Science Research Progress Report, pp. 68-70.
  • Miller, T.W. and C.R. Libbey. 1999. Response of three sweet corn cultivars to several herbicides. Western Society of Weed Science Research Progress Report, pp. 57-58.
  • Miller, T.W. and C.R. Libbey. 1999. Tolerance of cucumber, squash, and pumpkin to several herbicides. Western Society of Weed Science Research Progress Report, 62-64.
  • Miller, T.W. and C.R. Libbey. 1999. Volunteer potato management with herbicides and tillage. Western Society of Weed Science Research Progress Report, 59-61.
  • Miller, T.W. and C.R. Libbey. 1999. Response of newly-planted strawberry to pre- and post-transplant herbicides. WSSA Abstracts, p. 17. Weed Science Society of America, San Diego, CA.
  • Miller, T.W. 1999. Puzzled by Poaceae?--a grass identification workshop. November 3, 1999. Washington State Weed Control Conference, Yakima.
  • William, R., D. Ball, T.L. Miller, R. Parker, J.P. Yenish, T.W. Miller, G.A. Lee, and D.W. Morishita. 1999. Pacific Northwest Weed Control Handbook. Jointly published by OSU, WSU, and UI (380 pp.).