Progress 07/01/04 to 06/30/09
Outputs
OUTPUTS: Research Studies: 1. The main thrust of this AES project has been transferred to a Western Sustainable Agriculture Research and Education (SARE)-funded project in collaboration with J. Reeve, D. Drost, C. K. Evans, and R. Ward. This project, "Cultural management of onion thrips and iris yellow spot virus", was awarded $133,441 for 2008-11. Current research directions include evaluation of nitrogen (N) and crop management practices on thrips and iris yellow spot virus (IYSV), and attraction of thrips to trap crops to reduce their impact on the onion crop. Preliminary results: onion thrips densities were higher in plots with higher levels of N and in plots following cropping of wheat as compared to corn (likely because of higher N levels in soil of wheat plots); three species of trap crops (phacelia, carrot, and buckwheat) attracted thrips early in the season (May and June), but then repelled thrips in July and August. Future studies will continue to tease out the specific effects of crop management practices and trap crops on thrips and IYSV. 2. Insecticide efficacy against thrips in onion. The efficacy of cyazypyr (DPX-HGW86), methomyl (Lannate), and spinetoram (Radiant) were compared to an untreated control for suppressing populations of onion and western flower thrips (Thrips tabaci and Frankliniella occidentalis, respectively) adult, egg, and larva populations on dry bulb onion. Cyazypyr was efficacious against eggs and larvae of onion thrips. This insecticide has systemic activity with translaminar movement into leaves. Cyazypyr exhibited up to two weeks of activity against onion thrips larvae, up to one week of suppression of egg production, and up to two weeks of suppression of larval hatch from eggs in leaves following insecticide applications to field plots. Given that efficacy of Cyazypyr against thrips adults was low, this finding suggests that Cyazypyr has sublethal reproductive-suppressive effects that inhibits egg production or oviposition. In comparison, Radiant exhibited moderate suppression against adults and good activity against larvae, egg-laying and larval hatch from eggs. Lannate performed the best of the three insecticides tested. It showed good activity against all three life stages and suppressed larval hatch from eggs for up to two weeks after treatment. Publications Produced by the Project: 1. Alston, D. and D. Drost. 2008. Onion thrips (Thrips tabaci). Utah Pests Fact Sheet ENT-117-08 (7 pp.). Utah Plant Pest Diagnostic Lab and Utah State University Extension, Logan, UT. 2. Alston, D. and D. Worwood. 2008. Western striped cucumber beetle and western spotted cucumber beetle. Utah Pests Fact Sheet ENT-118-08 (7 pp.). Utah Plant Pest Diagnostic Lab and Utah State University Extension, Logan, UT. 3. Alston, D. G. and J. V. Barnhill. 2008. Squash bug (Anasa tristis). Utah Pests Fact Sheet ENT-120-08 (6 pp.). Utah Plant Pest Diagnostic Lab and Utah State University Extension, Logan, UT. PARTICIPANTS: Utah State University Agricultural Experiment Station (Kaysville) Utah Onion Association Onion growers Dan Drost, USU Professor and Extension Vegetable Specialist Jennifer Reeve, Assistant Professor and Organic and Sustainable Agriculture Program Director Marion Murray, Utah Extension Integrated Pest Management Project Leader C. Kent Evans, Assistant Professor and Extension Plant Pathologist TARGET AUDIENCES: Onion producers in Utah and other states, especially in the West Agricultural industry support businesses (farm products and chemical sales reps) Agrichemical company insecticide product development staff University extension (specialists and agents) and research faculty State and federal agency staff (UDAF, NRCS) PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
1. Utah onion growers have switched their primary onion thrips pest management strategy from sole reliance on repetitious insecticide applications to crop management (especially nitrogen and irrigation management), biological control, and rotations of reduced-risk insecticides. These changes impact approx. 2,000 acres of dry bulb onion production in Utah for an annual savings of approx. $180,000 and improved consistency in bulb quality and size. 2. Reduced insecticide use contributes to environmental impacts by reducing non-target effects on beneficial insects, water and soil quality, and ecosystem health. 3. Reduced insecticide use reduces human exposure to pesticides from farm applicators to onion consumers.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: ONION THRIPS LIFE HISTORY AND FIELD SURVIVAL: To complement previous field research results, an undergraduate student research project was directed during 2008 on "Effect of age on egg-laying capacity of onion thrips". Project results were presented in two poster sessions and the student won first place in the Department of Biology Undergraduate Research Symposium Spring 2008. Results were presented to onion growers at a winter educational meeting and at a summer field day. Results were shared with the broader onion production community at a regional crop management meeting in Denver, CO. CULTURAL MANAGEMENT OF ONION THRIPS AND IRIS YELLOW SPOT VIRUS: An off-shoot project was initiated with funding from WSARE. During 2008, 15 commercial onion fields were surveyed for thrips densities (adults and larvae on leaves, eggs within leaves, and adult on aerial traps placed in onion fields). Thrips densities will be compared to grower crop management practices and incidence of IYSV in fields. Grant funding continues for two more years. PUBLICATIONS: Three extension publications and four posters for presentation at meetings and symposia were produced from the project during 2008. PARTICIPANTS: Utah State University Agricultural Experiment Station (Kaysville) Utah Onion Association Onion growers Dan Drost, USU Professor and Extension Vegetable Specialist Jennifer Reeve, Assistant Professor and Organic and Sustainable Agriculture Program Director Marion Murray, Utah Extension Integrated Pest Management Project Leader Kent Evans, Assistant Professor and Extension Plant Pathologist TARGET AUDIENCES: Onion producers in Utah and other states, especially in the West Agricultural industry support businesses (farm products and chemical sales reps) Agrichemical company insecticide product development staff University extension (specialists and agents) and research faculty State and federal agency staff (UDAF, NRCS) PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Previous research supported the occurrence of a pre-oviposition period of 2-5 days in newly emerged onion thrips adults. Results from this project contradict this finding. We found no difference in the number of eggs laid between newly emerged (0-1-day-old) and 7-day-old female onion thrips. These results support field observations that onion thrips populations can increase rapidly after low numbers of adults are first detected on onion plants. This information will impact pest management recommendations to reflect that management practices should emphasize prevention and early detection of thrips populations. Outcomes have been promoted to growers through a new extension publication on onion thrips and at the 2008 onion field day; they will also be published in a refereed journal paper during 2009.
Publications
- Alston, D. and M. Murray 2008. Codling Moth Monitoring in Mating Disrupted Apple Orchards: Development of Trap Thresholds and Prediction of Fruit Injury. Final Report to Utah State Horticultural Association Research Committee and Utah Department of Agriculture and Food Specialty Crop Block Grant Program.
- Alston, D. 2007. Utah onion thrips insecticide efficacy trial: Influence of egg hatch, survival and immigration on insecticide performance in dry bulb onion. UAES Project and AgriChemical Industry Report, 16 pp.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Suppression of onion thrips (OT) (Thrips tabaci) and western flower thrips (WFT) (Frankliniella occidentalis) on dry bulb onions in small plots (12'x20') was evaluated from 3 approaches: 1) quick knock-down of motile life stages (short-term suppression), 2) reduction of re-infestation from the reservoir of eggs in leaves and egg hatch (longer-term suppression), and 3) reduction of re-infestation by adult immigrants (longer-term suppression). These approaches are based on thrips life history and sources of thrips for onion plants. QUICK KNOCK-DOWN: Using a whole-plant wash method, the efficacy of reduced-risk and conventional insecticides in suppressing adults and larvae was assessed. Adult OT were 10-100X more numerous than adult WFT. Adult OT were not consistently suppressed by any insecticide, whereas adult WFT were suppressed by many insecticides for up to 14 days after treatment. The insecticides Lannate (conventional carbamate with systemic activity) and Radiant
(derived from Saccharopolyspora spinosa toxin) consistently suppressed thrips larvae in two trials. Movento (tetramic acid with systemic activity) showed delayed effects of 2-3 weeks in suppressing larvae. It appears there is a delay in uptake and translocation of Movento within the onion plant, so an earlier application timing may enhance its efficacy on motile life stages. Resistance of larvae to Warrior (conventional pyrethroid) and Carzol (conventional carbamate) is suspected because a reduction in product efficacy after 2-3 years of use at the research site was observed. REDUCE RE-INFESTATION FROM EGG RESERVOIR IN LEAVES: Using an acid fuchsin leaf-staining method, thrips eggs were found to be numerous (13-113 eggs per 3rd youngest leaf or an estimate of 3X this many per plant). Eggs were estimated to compose 60-75% of the thrips on a plant while larvae composed approx. 15-30% and adults only 1-3%. Insecticides had little effect on reducing egg numbers in leaves and this was
similar to minimal effects on OT adults. Lannate and Movento suppressed egg hatch (determined by placing leaves in hatching chambers). Most eggs hatched within 1 week of collecting leaves from the field. REDUCE RE-INFESTATION BY ADULT IMMIGRANTS: Exclusion cages placed over plants and aerial sticky traps were used to evaluate the effects of adult immigration versus egg survival on populations on plants. In general, more thrips occurred on caged than open plants 2-3 wk after insecticide treatment. These results suggest that the reservoir of eggs in leaves is important to re-infestation of plants. The exception to this observation was for Lannate, Movento, and Radiant which provided longer-term suppression of thrips on plants. Flying adults were highly abundant. Approx. 150-300 adults were caught on a sticky trap per week after insecticides were applied. In conclusion, these studies show that egg survival in leaves and immigrating adults help perpetuate thrips populations on onions
following insecticide applications. Sustainable thrips management strategies should include longer-term suppressive tactics that target egg-laying and egg hatch.
PARTICIPANTS: Utah State University Agricultural Experiment Station (Kaysville) Utah Onion Association and multiple onion growers Dan Drost, USU Professor and Extension Vegetable Specialist Jennifer Reeve, Assistant Professor and Organic and Sustainable Agriculture Program Director Marion Murray, Utah Extension Integrated Pest Management Project Leader
TARGET AUDIENCES: Projected contacts for 2007 given in parentheses Onion producers in Utah and other states, especially in the West (300) Agricultural industry support businesses (farm products and chemical sales reps) (100) Agrichemical company insecticide product development staff (25) University extension (specialists and agents) and research faculty (50) Total estimated contacts for 2007: 475
PROJECT MODIFICATIONS: I have completed three full field seasons of research and the majority of the original project objectives. I have been granted a one-year project extension to complete several thrips life history experiments in the laboratory. I have added several new objectives for experiments that will complement the field-based studies. I am mentoring an undergraduate student in my lab who initiated several thrips life history experiments this past fall. The experiment objectives include: 1) assess egg-laying capacity of onion thrips adults, 2) evaluate the influence of temperature and adult thrips age (1-2 days versus 7-10-days-old) on egg-laying capactity, and 3) determine the rate of egg hatch and egg survival at several temperatures.
Impacts
Onion thrips are the most common cause for insecticide use in dry bulb onion production in western North America. Utah onion producers may apply 4-6 insecticide sprays per season to suppress thrips during the main bulb growth period in mid and late summer. Insecticide resistance is a major concern and limits the longevity of new insecticides in the agricultural market. Furthering our knowledge of onion thrips ecology and population response to reduced-risk insecticides will contribute to more sustainable thrips management strategies and annually save Utah onion producers up to $1 million in reduced insecticide costs, avoidance of insecticide resistance, and improved crop quality. Our data suggest that onion thrips eggs within leaf tissue are a main contributor to thrips populations on plants. Once onion thrips become established in a field, egg survival, even following insecticide applications may play a greater role in perpetuating the population than even adult
immigration. Onion thrips suppression strategies should include longer-term prevention of egg-laying and egg hatch to enhance population management in onion fields. My focus has now turned to educating onion pest managers (growers, crop consultants, agricultural product sales representatives) on the role of thrips egg reservoirs on population management. I will have an economic impact on improving the sustainability of onion thrips management and reducing producer costs (see cost estimate above). I have shared my onion thrips story (data) with Utah growers at several winter educational meetings and I will give a presentation at the Rocky Mountain Agribusiness Association (200-300 crop consultants will be present) in Denver, CO in January, 2008. I published preliminary results in the major onion industry trade magazine, "Onion World" in 2006. I hope to have the opportunity to publish a follow-up article with more comprehensive information within the next year or two. I have initiated a
refereed research publication and plan to submit it by spring of 2008. I will write a comprehensive extension fact sheet on onion thrips management during 2008. I believe that all of these methods of outreach will expand the number of contacts with the onion industry as well as university research and extension staff. I believe that based on the number of contacts I received following publication of the "Onion World" article, including the invitation to speak to the Colorado crop consultants, that the agricultural community is interested in my unique research findings and the IPM-based story I have to share.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
THRIPS SAMPLING METHODS: We modified a whole-plant wash technique where leaves are cut at the top of the bulb, placed in a jar with soapy water, washed over a 250-mesh sieve, and the thrips washed into a vial with ethanol for counting under the microscope. We found that thrips densities were consistently higher and life stages (larva, pupa, and adult) easier to distinguish in whole-plant wash samples than in situ counts. We modified an acid fuchsin method to stain eggs of thrips within leaf tissue. Protein in eggs will stain a dark pink color and a clearing reagent removes much of the stain from leaf cells. We also modified an aerial sticky trap to monitor adults. PVC pipe (4 inch diameter) was cut into 6 inch sections, painted with low reflectance (i.e., flat) white paint, covered with sticky fly paper, and mounted on wooden stakes at plant canopy height. Aerial traps were more effective at monitoring adult thrips populations than the whole-plant wash or in situ
methods. THRIPS SURVIVAL AND IMMIGRATION: To gain a better understanding of the influence of thrips survival and immigration on populations in fields, we placed cages over plants to exclude and enclose thrips on plants. Cages were made from fine mesh no-see-um screening designed for tents and outdoor enclosures. Following application of insecticides or no application (untreated control), three thrips exclusion treatments were imposed on plants: 1) plants were left open to allow ongoing dispersal and influence of natural enemies, 2) plants were caged to exclude new immigrants, and 3) plants were sprayed thoroughly with insecticidal soap to kill all mobile stages and then caged to exclude new immigrants. Following two field seasons' of data collection, results have shown the importance of egg survival to thrips populations on plants. As expected, insecticide applications reduced thrips densities on plants two weeks later, but exclusion of natural enemies and/or enclosure of newly
hatched thrips resulted in higher numbers of thrips on caged than open plants. The magnitude of this effect was similar between untreated and insecticide-treated plants suggesting that hatching eggs contribute a significant proportion of thrips populations on plants. CONTRIBUTION OF EGGS TO PLANT POPULATIONS: Studies to directly evaluate the influence of insecticides on egg hatch and viability found differential egg hatching rates across treatments. Numbers of hatched larvae were greater two than one week after treatment in all but the Warrior-treated plots. And significantly more eggs hatched from Surround, Stylet oil (1% and 2%), and untreated control treatments than from Success, Carzol, and Warrior treatments. The cumulative number of larvae that hatched from two onion leaves over the two-week period is noteworthy. We found cumulative totals of 6-28 hatched larvae across the treatments, again supporting the important contribution of eggs to thrips populations on plants.
Impacts
Onion thrips are the most common cause for insecticide use in dry bulb onion production in western North America. Utah onion producers typically apply 4-6 insecticide sprays per season to suppress thrips during the main bulb growth period in mid and late summer. Insecticide resistance is a major concern and limits the longevity of new insecticides. Furthering our knowledge of onion thrips ecology and population response to reduced-risk insecticides will contribute to more sustainable thrips management and annually save Utah onion producers up to $1 million in reduced insecticide costs, avoidance of insecticide resistance, and improved crop quality. Our data suggest that onion thrips eggs within leaf tissue are a main contributor to the thrips populations on plants. Once onion thrips establish in a field, egg survival even following insecticide applications may play a greater role in perpetuating the population than adult dispersal. Onion thrips population suppression
strategies should consider prevention of egg-laying and egg hatch to enhance population management in onion fields.
Publications
- Alston, Diane. 2006. Onion Thrips Research in Utah: Contributions of Life Stage Survival and Adult Dispersal to Populations on Onion. Onion World November/December 2006
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Progress 01/01/05 to 12/31/05
Outputs
2005 experiments were conducted in a 0.22 acre field of Vaquero dry bulb onion at the Utah State University Experiment Station in Kaysville, UT and in three commercial onion fields in Syracuse, UT. New and lower toxicity insecticides were compared to conventional insecticides for efficacy on onion thrips population suppression during the peak onion bulb growth period from July to early September. Thrips sampling methods used were whole onion plant wash with soapy water, acid fuchsin onion leaf stain to view eggs, and aerial sticky traps (white PVC pipe covered with clear sticky fly paper). Insecticide treatments were: untreated control; a new, numbered material from Bayer at 6 oz and 8 oz/acre + 0.5% methylated soybean oil (MSO); Success at 5 oz/acre +1% stylet oil; Diatect (diatomaceous earth and pyrethrins) at 3 lb/acre + 1% stylet oil; Safers insecticidal soap at 2.5 oz/acre + 2% neem oil; 1% stylet oil; and Mustang at 4 oz/acre + 1% stylet oil. The Bayer
insecticide treatments were applied once and thrips densities determined weekly for 4 weeks post-treatment, whereas all other insecticides were applied twice (after 2 weeks) during the trial. Cumulative numbers of onion thrips larvae for the 4 week trial period (mean cumulative values of 30-210 per plant) were significantly reduced (p<0.05) in Success, Bayer at 8 oz/acre, Mustang, Diatect, insecticidal soap, and stylet oil treatments as compared to the untreated control. Cumulative numbers of onion thrips eggs (mean cumulative values of 190-640 per leaf) were significantly lowered only in Success as compared to the untreated control. Adult densities were low throughout the trial (mean of 1.5 to 9.3 adults per plant on any single sample date) and were not influenced by insecticides. Using an economic threshold of 20 larvae per plant, Success, the Bayer material at 8 oz/acre, and Mustang kept onion thrips densities below this threshold on most post-treatment dates. The high rate of the
new Bayer material performed especially favorably considering that it was applied only once rather than twice during the trial. Onion thrips life stage demonstrates the relative composition of populations on plants. Adults composed only 1-3% of the population, whereas larvae and eggs composed 15-30% and 60-75% of the population on plants, respectively. In contrast, aerial sticky trap results showed high densities of onion thrips adults (mean values >300 adults per trap per week on most sample dates) dispersing within onion fields suggesting that adults spend more time dispersing than resting on plants. Additions of oils, spreaders stickers, and other surfactants may improve the residual efficacy of insecticides. High densities of onion thrips eggs within leaf tissue contribute a major proportion of the thrips populations on plants and should be a focus of on-going population suppression.
Impacts
Onion thrips are the most common cause for insecticide use in dry bulb onion production in western North America. Utah onion producers typically apply 4-6 insecticide sprays per season to suppress thrips during the main bulb growth period in mid and late summer. Insecticide resistance is a major concern and limits the longevity of new insecticides. Furthering our knowledge of onion thrips ecology and population response to reduced-risk insecticides will contribute to more sustainable thrips management and annually save Utah onion producers up to $1 million in reduced insecticide costs, avoidance of insecticide resistance, and improved crop quality.
Publications
- Alston, D. G. 2005. Onion thrips management with reduced-risk insecticides. Proceedings of the Utah Onion Association Winter Meeting, February 15, Ogden, UT.
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Progress 07/01/04 to 12/31/04
Outputs
A 0.2 acre plot of onions was planted at the Kaysville Experiment Station and four project objectives were addressed in 2004. COMPARISON OF THRIPS SAMPLING METHODS: Thrips densities were consistently greater for the whole-plant wash than the in-situ count method. Thrips life stages on leaves (larva, pupa, and adult) could be distinguished in whole-plant wash samples, whereas life stages could not be separated in in-situ counts. The majority of thrips on onion plants from August 5 to September 2 were onion thrips, Thrips tabaci (95.1%). Western flower thrips, Frankliniella occidentalis, and predaceous thrips composed the remainder of thrips found on plants (4.7 and 0.2%, respectively). EFFICACY OF INSECTICIDES: Success (spinosad, an actinomycete), Diatec (diatomaceous earth + pyrethrum + piperonyl butoxide), Mustang (zeta-cypermethrin, a synthetic pyrethroid), and supreme oil were evaluated for their efficacy in suppressing thrips densities on onions. Success and
Mustang alone and with oil significantly suppressed thrips densities for two weeks post-treatment as compared to untreated plants, whereas thrips densities treated with Diatec (alone and with oil) and oil were no different from the untreated control. In whole-plant wash samples, the larva was the main life stage recovered (74.0% of total onion thrips). There were fewer adults (21.7%) and pupae (4.3%) present. In addition, densities of thrips eggs per leaf were determined by an acid fuchsin staining method. Egg densities were variable; however, they did not differ significantly among treatments across dates. In general, treatments with oil had fewer eggs than treatments without oil and the untreated control. THRIPS SURVIVAL VS. IMMIGRATION: One set of onion plants was caged immediately after insecticides were applied to exclude immigrating thrips. Thrips densities were similar or greater on caged than open plants when compared within treatments. This trend occurred for untreated and
insecticide-treated plants. Cages may have elevated temperatures on plants, thus increasing thrips development and reproduction rates. Although higher temperatures inside cages may have stimulated thrips densities, these results also indicate that enough thrips survived insecticide treatments to be a major contributor to on-going populations on plants. RELATIVE IMPORTANCE OF EGG SURVIVAL: Another set of onion plants was sprayed with soapy water before insecticides were applied to remove motile life stages and then caged following insecticide treatments to exclude immigration. Relative densities of thrips between caged plants with and without the soap application varied across treatments, but in general were similar. If motile thrips life stages were effectively removed by the soap spray, then survival of eggs within leaf tissue was the major contributor to thrips populations on plants following insecticide treatments.
Impacts
Onion thrips are the most common cause for insecticide use in dry bulb onion production in the western U.S. Insecticide resistance is a major problem for onion thrips and limits the longevity of new insecticides. Furthering our knowledge of onion thrips ecology and population response to reduced-risk insecticides can lead to more sustainable thrips management and annually save Utah onion producers up to $500,000 in reduced insecticide costs and improved crop quality.
Publications
- No publications reported this period
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