Spotted Wing Drosophila

We caught our first spotted wing drosophila adults in traps in Elkhart County over the weekend. We can assume that they will be flying and laying their eggs in developing fruit of grape, raspberry, blackberry, and blueberry from this point until the end of the season. In addition to checking traps, growers should be inspecting fruit on a regular basis. Last year at the Meigs Farm near Lafayette, we were using three different types of traps/baits, and we still found maggots in raspberries before we caught the first fly in a trap. We have no spray thresholds for SWD, so in general we recommend spraying if any flies are being caught in traps or if any maggots have been observed in fruit. Below is a list of recommended insecticides. If possible, growers should rotate between classes of insecticides to avoid the development of resistance. So, if you used Mustang Maxx one week, you should not use that insecticide or any of the other pyrethroid insecticides the next week. Choose an insecticide from a different class because it has a different mode of action and resistance is less likely to be a problem. Another important question is how often to spray. Many growers have had good success spraying weekly, but others are spraying as much as twice per week. If weekly sprays have worked for you, I would recommend continuing that practice. If not, I would encourage you to shorten the interval to about 5 days. Be sure to observe the PHI (pre-harvest interval) and REI (re-entry interval) restrictions on each product.