SWD Update 16 July 2012
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Spotted Wing Drosophila Update
By the SWD Team
July 20, 2012
Blueberry harvest is now in full swing in the Willamette Valley. Fruit quality is good and the total production is expected to exceed the 2011 season. With many acres of mid- to later- season varieties planted in the past few years, Oregon is in a strong position to meet increased demand for late season fresh fruits. Meanwhile, late season fruits are more vulnerable to SWD infestation because SWD populations tend to peak after late-July as seen in the past two seasons. Appropriate chemical applications are needed to protect fruits against SWD especially for late season blueberries.
SWD season update
Historic SWD trap counts using apple cider vinegar (ACV) bait indicate relatively high numbers in late January with decreasing overwintering adult fly numbers from March to April. SWD trap catches indicate higher populations (primary y-axis) this season compared to the same period in 2011, which may be due to milder winter temperatures (graphs below, thinner lines indicate average temperatures for each season on the secondary y-axis). Figures below show seasonal differences of SWD trap counts in a Hillsboro blueberry field.
SWD research in blueberry
Larval extraction: In replicated lab studies, crushing or breaking open blueberry fruits significantly improved SWD larval extraction using a salt or sugar solution (1 cup salt or 3 cups white sugar dissolved in 1 gallon warm water). Cover broken fruits in a shallow pan, and closely observe the surface of the solution for larvae under good light conditions. SWD larvae will float on the surface of the solution within 15 minutes.
Laboratory and field studies indicate the efficacy of carbaryl is intermediate. OPs, synthetic pyrethroids, and spinosyns provide the most consistent control. Entrust is the most effective organic product available, while recent lab studies indicate female SWD treated with Pyganic can recover and lay fertile eggs. Growers should be advised of reports of fruit spotting due to the use of oil-based formulations of malathion.
SWD control in blueberry
Monitoring: Begin immediately prior to blush of color through harvest. Place ACV traps (concentrating on field margins) inside blueberry plant canopy to provide some shade. Replace ACV bait weekly and check for SWD presence. For detailed monitoring information, visit spottedwing.com.
Control and bee awareness: Currently, SWD control relies primarily on insecticides. Please consult the PNW Insect Pest Management Handbook (uspest.org/pnw/insects) for more details regarding control of SWD. When applying pesticides, limit the impact on bees by applying compounds during decreased bee activity such as late dusk. Minimize attraction into crop fields by controlling pollen and nectar producing in-row cover crops such as dandelions.
Editor: Wei Yang
Contributing authors: Amy Dreves, Denny Bruck, Jana Lee, Jimmy Klick, Joe DeFrancesco, Vaughn Walton