Spotted Wing Drosophila (SWD) Pre-season Notice
Spotted Wind Drosophila
The UMass Extension Vegetable & Fruit IPM team is monitoring 10 sites across the state for Spotted Wing Drosophila (SWD) in 2015. Traps will be set out at these sites over the next week and will be checked weekly or biweekly throughout the summer to monitor the development of this pest and inform alerts that will go out to fruit and vegetable growers and others. Detailed updates will be distributed via this newsletter (IPM Berry Blast), but will also be available in a more abbreviated form via different channels including Facebook, twitter, and as direct email or text alerts.
Click Here to sign up for SWD email or Text alerts (you may also sign up for BMSB alerts here, too). You will receive an email that asks for you to confirm you desire to receive these emails and/or texts. Your registration won't be complete until you complete this step. (photos courtesy of Dr. Alan Eaton, UNH Extension)
- Keep rows of raspberries narrow at the base (18") and thin canes to allow 6" between canes if possible to allow for good air circulation and light penetration. In blueberries, eliminate branches below knee high (on mature bushes) that cast shade on the ground and open the upper canopy to allow for good air circulation and light penetration. This will improve spray penetration and efficacy, too. In other berry crops, maintain an open canopy as much as possible
- Growers should set out and monitor traps in their fields to know what is happening on their farms by mid June or before susceptible fruit begins to color.
- Remember to harvest frequently (daily if possible), and thoroughly and avoid allowing fruit to fall to the ground if possible.
- Transport harvested fruit as quickly as possible to refrigeration.
- Spray recommended materials (organic or conventional) on a tight schedule (5-7 days) once crop is ripening and SWD have been confirmed at or near the crop. Some recommend spraying in the evening to increase residual efficacy because some materials degrade more quickly in sunlight. SWD may also be more active in the evening especially when the weather is very hot. Also, it is recommended to add 2# of sugar per 100 gallons of spray solution to all materials except pyrethroids (which don't show increased efficacy from this addition).
- Sample fruit regularly during harvest and do salt flotation test to determine SWD larval presence and density.
Entrust - Spinosad Overuse Warning
Dr. Richard Cowles, Connecticut Agricultural Experiment Station
Here is a “shot across the bow” from Dow AgroSciences. This is not an idle threat to withdraw sales of Entrust to New England states. Abuse of Conserve SC by greenhouse growers in the Southeast led to widespread flower thrips resistance, whereupon Dow withdrew marketing of that product to that region.
The problem that I see is that there currently are very few effective proven alternative options to spinosad available to organic growers, besides frequent clean harvesting of crops and use of exclusion netting (for certain crops).
The risk of insecticide resistance developing with this pest is debatable. Its extreme mobility and development in so many untreated wild hosts would suggest that resistance, if it were to develop, would be an “in house” problem during a single season on individual farms, and that later mixing with wild type flies could counteract the evolution of resistance. However, knock down and recovery from pyrethrin exposure by SWD flies is suggestive that selection for resistance with other classes of insecticides may already be occurring, and there are ample reasons for concern.
Growers (not only organic producers) should be advised that they should intensively monitor for SWD adult activity with effective traps and baits, and only consider insecticide sprays when both (a) SWD adults are present and (b) fruit are ripening sufficiently to almost be susceptible to egg laying. Please emphasize to growers the importance of following the label directions of pesticides in all regards, including the limitations for use of Entrust on individual crops and on entire farms, due to concerns for insecticide resistance prevention.
Archived IPM Berry Blasts are available at the UMass Extension Fruitadvisor website.
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