Spotted Wing Drosophila Captured in Western Kentucky

We have identified our first spotted wing drosophila (SWD) of 2014 in western Kentucky. It was present in a trap maintained by Patty Lucas in the Purchase Area of the state. The timing of this capture is very close to the date of our first report last year. A trap had one female on June 12, and those same traps had 5 females the following week (Figure 1). Based on our experience in 2013, SWD captures are likely to spread across the Commonwealth over the next 2 to 4 weeks and intensify as the season progresses.

Figure 1. Spotted wing drosophila females on a blackberry. (Photo: Ric Bessin, UK)

Figure 1. Spotted wing drosophila females on a blackberry. (Photo: Ric Bessin, UK)

Management

Producers of susceptible crops (raspberries, blackberries, blueberries, and grapes) that still have crops in the field should put out spotted wing drosophila traps, if they haven’t already done so.

Traps and Bait

We use 1-quart deli containers with a pair of 1 ½ -inch by 3-inch windows cut in the sides. We hot-glue ¼-inch plastic screen over these windows to keep out larger flies (Figure 2). The bait is a mixture of baker’s yeast, sugar, water, and dishwashing soap. To make enough bait for two traps, mix ½ tablespoon yeast with 1 tablespoon sugar, 1 cup water, and one drop of dishwashing soap. Check the traps weekly, pour the contents into another container for identification, and refill the traps with fresh bait. To clean the samples, pour the contents through a reusable coffee filter and rinsing with water to clear out the yeast.

Figure 2. A spotted wing drosophila trap. (Photo: Ric Bessin, UK)

Figure 2. A spotted wing drosophila trap. (Photo: Ric Bessin, UK)

Interpreting Trap Findings

If you don’t find SWD, you do not need to spray insecticides during the harvest period. If you do find SWD, then you need to begin a concerted SWD management program. It may mean spraying during the harvest period, so producers need to carefully observe all pesticide label instructions including Pre-Harvest Intervals. Sprays for SWD need to provide excellent coverage, so pressure and spray volume need to be sufficient for coverage throughout the canopy. Reapply  sprays on a weekly basis, as well as after a significant rain. Check Entfact 230 (listed in the resources, below) for a list of SWD recommended insecticides and their respective pre-harvest intervals.

Other Management Tactics

It is important to use other SWD management tactics besides only relying on sprays.

Netting

Producers not wanting to use insecticides may use fine mesh netting.  The netting needs to have a mesh size fine enough to prevent SWD females from passing through, so pore sizes of less than 0.98 mm are needed. The netting needs to be sealed around the base and in place before fruit begin to ripen.

Clean Harvest

Clean harvest is also a key management tool. For clean harvest, pickers use two containers when picking, one for marketable fruit and the other for all other ripe fruit. Removing the unmarketable fruit from the field reduces the buildup of SWD.  Unmarketable fruit should be placed in clear bags, sealed, and left in the sun.  Burying SWD-infested fruit is ineffective as this insect has been shown to emerge from the soil.

Post-Harvest Care

Post-harvest care of berries is another important management tool. As soon as berries have been harvested, they need to be refrigerated. This suspends the development of SWD by delaying egg hatch, growth, and feeding by larvae (Figure 3). Temperatures as close to but above freezing are best.  Freezing berries will kill all immature stages.

Figure 3. Spotted wing drosophila larvae infesting blueberry. (Photo: Ric Bessin, UK)

Figure 3. Spotted wing drosophila larvae infesting blueberry. (Photo: Ric Bessin, UK)

More Information

See our factsheets for a description of biology, identification, and SWD management:

 

By Ric Bessin, Extension Entomologist

 

Posted in Fruit