Spotted Wing Drosophila (SWD): Substantial Increase in Trap Catch for Southern MN Confirms Need for Conservative Spray Programs

July 12, 2017

Bill Hutchison, Eric Burkness, Dominique Ebbenga, Adam Toninato & Suzanne Wold-Burkness 
MN Extension IPM Program, Dept. of Entomology, Univ. of Minnesota, St. Paul campus 

During past week, July 3-10th, we observed a significant increase in SWD adults collected at several trap locations in the Twin City Metro area. For example, high catch rates of 70/week were found at Hastings (grapes), with over 110/week/trap observed at Andover. The timing of the increase also coincided with the mid-July increase we saw in 2016. Again, all SWD Trap sites are summarized weekly at: https://www.fruitedge.umn.edu/swdtrap

Growers of all susceptible berry crops, including summer raspberries and blueberries should be prepared to manage SWD with conservative spray programs, as well as timely and clean harvests. Conservative spray programs include maintaining a 5-day spray interval, rotating at least 3 insecticides from different classes, such Delegate/Entrust (spinosyn, bacterial based), Mustang Maxx (pyrethroid) and malathion (organophosphate). These products have shown the most consistent efficacy against SWD, and have pre-harvest intervals of 1-day. This allows some flexibility in scheduling harvest dates between sprays. In addition it is Critical to have Clean harvests, to not leave over-ripe or rotting fruit on the ground – as this is a great refuge for SWD populations to continue to build up on a farm. For more information, including organic-certified products, see the FruitEdge web site (www.fruitedge.umn.edu) and SWD pages. IPM guidelines will continue to be uploaded to this site, including new information about a recently approved product, Grandevo, as well as more information on how to order exclusion netting for berry crops, and cost/benefit information. In our opinion, Exclusion netting is the best long-term solution to manage SWD with zero or very little insecticide use, and we have 2 years of data to support this for fall raspberries. However, there are still very few suppliers, and the initial capital investment is high. We are hopeful more suppliers will enter the market to help bring more competitive pricing.

Additional, recent IPM updates for SWD are also available for MN growers, via Michigan State, in this June issue of, Fruit Growers News article. Finally, although Japanese beetles are now active, and clearly enjoy feeding on raspberry and other berry crops, they are easy to control with the insecticides that are being used for SWD.

SWD adults 2016