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Funded Project |
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Funding Program:
Regional IPM Competitive Grants - Northeastern |
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Project Title:
Spotted Wing Drosophila Management |
Project Director (PD):
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Lead State: CT Lead Organization: CT AES |
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Cooperating State(s):
New Jersey, New York, Rhode Island, Washington |
| Undesignated Funding: $161,985 |
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Start Date: Sep-01-2012 End Date: Aug-31-2015 |
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Site/Commodity: spotted wing drosophila |
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Summary:
This is a research project. The spotted wing drosophila (SWD), Drosophila suzukii, is a highly invasive pest that infests small fruits (raspberry, blueberry, strawberry, and grapes) and tree fruits (most notably, cherries). First found in New England on August 19, 2011, this pest over the next month caused $500,000 - $1,000,000 in losses to fruit growers in New England due to unsaleable maggot-infested fruit. Late fruiting blueberries, most fall-bearing raspberries, many wine grapes, and day-neutral strawberries were lost. Current SWD management recommendations from the Northwest suggest weekly applications once fruit start to ripen with methomyl, malathion, advanced generation pyrethroids, or spinosyns. Except for spinosyns, sprays of these products will set back decades of IPM progress by eliminating the beneficial predators and parasites in these crops. Such intensive use of pesticides on these crops is expensive, selects intensively for insecticide resistance, and leaves residues on fruit. This project will test in four small fruit crops in three states attractant and phagostimulatory baits combined with insecticides, some of which are organically acceptable, to manage SWD. Methods to compare will be conventional spray, bait spray applied to the crop, attractant plus bait applied to vegetation surrounding the crop, and insecticidal bait stations. Efficacy will be assessed by measuring insect activity and fruit infestation. We will investigate dipteran-specific Bacillus thuringiensis and Entomophthora muscae for deployment either with bait sprays or stations. Pest management methods developed in this proposal will provide science-based pest management that improves human and environmental health by minimizing the need for sprays of broad spectrum insecticides.
Objectives:
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Interim Report: Dec-06-2013 |
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Impacts Growers have already, to a large extent, adopted the use of 2 lb per 100 gallons of sugar with their insecticide applications to manage SWD, and the instruction for use of sugar is routinely included in instructions to growers from extension fruit specialists in New England. Extension fruit specialists have benefited from this project by having the best information available at the time for designing traps and attractants for monitoring SWD adult activity. In 2012, they used a grape juice, apple cider vinegar, and ethanol combination based on PJL's work demonstrating that apple cider and red wine were synergistically attractive. Extension personnel were not permitted to purchase red wine to make attractant baits, and so RSC tested the red wine/vinegar combination vs. the vinegar/grape juice/alcohol (VGA) combination and found that they were equivalent. In 2013, undergraduate students working with SRA designed a trap that combined the VGA bait as a drowning solution with a vial containing actively fermenting bait. RSC then took this design and modified it further, based on field attractancy assays, to use apple cider vinegar plus alcohol as the drowning solution, and added whole wheat flour to the standard yeast bait to improve its performance. This combination lure system was highly effective for monitoring SWD populations. Glen Koehler, Univ. Maine Cooperative Extension, has estimated that the trap network using these effective lures and timely communication to growers may have saved $6 million of crop damage by SWD in 2012 alone (NERIPM, Integrated Pest Management Insights, Spring 2013). Cooperative extension fruit specialists from New England and New York were trained at two meetings at the Valley Laboratory of the Connecticut Agricultural Experiment Station, one each in 2012 and 2013, organized by Glen Koehler, and supported by NERIPM. Training involved the design of traps, and coordination in their use, as well as discussions of using sugar in baited insecticide sprays. In addition, this information has been extended through web-based information and at growers' meetings. |
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Outcomes Objective 1) The addition of 2 lb per 100 gallons of spray mixture was found to enhance most insecticides in the field/laboratory bioassays. The field assessment method was found not to be efficient, probably because SWD adults are too mobile and so plot treatment effects are homogeneous unless conducted in caged tests. Growers have already adopted this technique to improve management of SWD. Objective 2) Strains of Bacillus thuringiensis from the USDA collection were found to not be toxic to either SWD adults or larvae. No further strains of Bt will be tested. Objective 3) Two locations (one in NJ, one in CT) were found with Drosophila cadavers infected with Entomophthora muscae. Attempts to reinitiate sporulation from these cadavers and cause infection in Drosophila have so far been unsuccessful, but are continuing. Objective 4) Vinegar caused dosage dependent phytotoxicity to open blossoms and foliage. Apple cider vinegar titrated to pH 6 and applied at 10% dilution causes no injury to either foliage or flowers, however. Because we have not found vinegar by itself to be particularly attractive to SWD adults, we are not pursuing spraying vinegar to manipulate their behavior. Objective 5) Baits and traps tested in 2013 were highly competitive with nearby fruit (as determined by significant trap catches). Attractant baits that perform well in competition with ripe blueberries and raspberries include a thin whole-wheat fermenting bait, SuzukiiTrap bait manufactured by BioIberica Company, and experimental formulations being designed in collaboration with ISCA Technologies (Riverside, CA). Attractancy relative to apple cider vinegar (assigned a value of 1) for the various baits are approximately 3 for synthetic lures (PJL lab), 7 for the standard yeast bait (Rufus Isaacs, Michigan State University), 14 for the SuzukiiTrap bait (BioIberica Co., Spain) and the thin whole wheat plus apple cider vinegar recipe (RSC lab), 28 for an experimental formulation from ISCA Technologies, and 50 for a raspberry infused vinegar. The CRS lab efforts have determined that raspberries are the most attractive undamaged host to SWD, and so it is clear that addition of raspberry or other cane fruit volatiles to attractant mixtures will greatly increase their attractancy. The most effective trap design was found to be the red cup trap with a black stripe, into which is punched 40 one-eight inch diameter openings for flies to enter. These holes are small enough to exclude many non-target insects collected by other trap designs (such as the modified McPhail trap). In a key experiment the number of flies captured through drowning in these traps was found to only be about 10 30% of the total number of flies visiting the surface of the traps, indicating that placement of phagostimulant-laced insecticide on outside of these traps will be essential for improving mass trapping. |
Report Appendices
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Interim Report: Feb-24-2015 |
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Impacts Growers are increasingly accepting the addition of 2 pounds of sucrose per 100 gallons of spray mixture to enhance the activity of many insecticides when targeting SWD adults. Extension fruit specialists have continually been able to improve the monitoring methods for SWD activity in growers fields, based upon contributions from this project with respect to understanding both trap design and the attractant baits used with those traps. Three out of the four growers integrating use of a spinosyn insecticide foliar spray with attract and kill traps treated with sucrose and boric acid never needed to apply the foliar spray, as the capture of flies never reached the spray threshold. This experience suggests that intensive monitoring and trapping of flies may limit the need to apply sprays to fruit. |
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Outcomes Objective 1) The effectiveness of sucrose as an adjuvant to increase the activity of insecticides targeting SWD adults was confirmed with small plot field trials in blueberries and strawberries. The most effective insecticides were enhanced the most with the addition of sucrose. Spray programs using only biorational or reduced risk insecticides were demonstrated to be as or more effective, when combined with sucrose, to spray programs relying on pyrethroids and/or organophosphate insecticides; biorational insecticides applied without sucrose were less effective. Objective 2) Approximately 150 strains of Bacillus thuringiensis obtained from the USDA collection were found to not be toxic to SWD adults or larvae. No further strains will be tested. Objective 3) An epizootic of Entomophthora muscae in the summer of 2014 afforded an opportunity to directly expose SWD adults to freshly sporulating anthomyiid cadavers. No infections of exposed SWD adults were observed. Objective 4) The use of vinegar, applied directly to crop plants as an attractant, was not pursued further as we demonstrated that it was too phytotoxic to be used and was not and effective attractant, either. Objective 5) The red cup trap was used in field trials in five states in a critical test of the attract-and-kill concept. Because we had concerns regarding confounded factors influencing the results from a 2013 mass trapping trial in Rhode Island, we carefully matched pairs of fields to either have traps treated with sugar and boric acid (10% and 5% in water solution, sprayed onto the outside of the cup) or no traps. Traps were placed on a 20 by 20 foot grid within the trapped field, and populations of flies monitored weekly. The effect of trapping was measured by collecting sound, ripe fruit and rearing out SWD adults. The outcome was that we did not find evidence of protecting fruits with this attract-and-kill attempt. Factors that may have limited the effectiveness were (1) the boric acid treatment appears to be a much slower acting toxicant than expected, (2) the boric acid appeared to selectively kill male SWD within these fields, and (3) there may have been insufficient traps, relative to the overabundance of fruit and the influx of immigrating flies, to adequately influence the SWD populations. We have continued efforts to design and test more practical and less expensive components for mass trapping SWD, or for conducting attract-and-kill trials. Kombucha was tested as an alternative to the fermenting whole wheat dough-based baits. It appears that kombucha, produced by fermenting sugar-water with both yeasts and acid-forming bacteria, can be a highly attractive bait, and can be produced at a cost of about one dollar per gallon. The red cup traps are difficult to work with for attract-and-kill programs because insecticide applied to the surface needs to be protected from rainfall. An alternative modified McPhail trap was designed from a two-liter plastic soda bottle (with material costs of about seven cents per trap). In field tests, this design was equivalent in performance to the Trappit dome trap, costing about twelve dollars per trap, and several times more efficient at capturing flies than the red cup trap. Attempts to design baits with synthetic attractants have been successful with collaborators on the west coast (Dong Cha and Peter Landolt), by simulating the aroma of combinations of wine and vinegar. Attempts in my lab and by Cesar Rodriguez-Saona to capture the attractive qualities of raspberries, both from authentic raspberry distillate and from synthetic odor blends, resulted in materials that appeared highly attractant in laboratory trials but were poorly attractive in field tests. |
| Report Appendices |
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Final Report: |
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Impacts Growers are now much better able to determine the presence and abundance of SWD through our efforts to test and improve upon baits and traps for this pest. Fewer pesticide applications, and of materials less disruptive to the environment, are now needed to manage SWD in crops sensitive to damage by this pest. |
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Outcomes New knowledge was developed as a result of this project. (1) The most effective attractant baits and traps were tested in the field, and those results were used by extension specialists and growers to influence their management decisions for SWD. Glen Koehler estimated that growers saved several million dollars worth of fruit as a result of more effective pest monitoring. (2) Knowledge that the addition of sugar to insecticide sprays makes those sprays much more effective in targeting SWD has resulted in the adoption of this practice by many growers. This research article was reported on as a news story by the Entomological Society of America, and so obtained international attention. |
Report Appendices
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