We have had our first spotted wing drosophila (SWD) detection for 2016. Patty Lucas, UK Extension IPM Specialist, recovered one SWD male (Figure 1) from a trap yesterday in strawberries in Caldwell County (western Kentucky). Over the 4 years Kentucky has had this invasive pest, the first capture has been earlier each year. So, are SWD really becoming active earlier each year, or are traps becoming more effective so that SWD is captured at lower numbers, or are we just better at placing the traps in the right place at the right time? We don’t know.
Monitoring and Spraying
So now that we have captured the first SWD, what does this mean? For that particular field using an insecticide weekly to control SWD is warranted through the remainder of harvest. This does NOT mean that other fields throughout Kentucky need to be sprayed. It stresses the need for producers to monitor for this pest in their own fields. Last year, although we began trapping SWD on May 27, the numbers caught in traps remained very low until the start of blackberry harvest when SWD numbers in traps increased dramatically. Traps in Fayette, Allen, Crittenden, Pulaski, Larue, and Daviess have been negative for SWD … so far.
Although our first capture in 2015 occurred during the strawberry harvest period, we did not detect or have any reports of SWD in strawberries. Commercial strawberry producers are advised to monitor for fruit infestations on undamaged berries by using the floatation method weekly. This method is listed in the second factsheet referenced below.
In some regions of the country, producers must meet zero tolerance requirements for insect infestation of the fruit when shipping blueberries, blackberries, or raspberries for wholesale marketing. Many of these producers do not have enough confidence with waiting to spray for SWD based on detection in traps and instead spray preventively to meet these strict requirements. Many of the Kentucky small fruit producers market crops locally and can tolerate a very low level of infestation by working directly with consumers. Trapping and spraying as needed has worked well in Kentucky and has been the most economical for our growers.
For a list of recommended insecticides for SWD on various crops, see:
- Spotted Wing Drosophila Management (Entfact 230)
For a list of cultural and physicals controls for SWD, see:
- Spotted Wing Drosophila and Backyard Small Fruit Production (Entfact 231)
By Ric Bessin, Extension Entomologist