Spotted Wing Drosophila Monitoring Report June 22, 2016

— Written By Grant Palmer and last updated by

We have now processed traps through the week of July 6th. Blackberry trap captures of spotted wing drosophila (SWD) are continuing to drop, and available fruit are likely more attractive than our traps.

Because SWD are invasive species, native predators and parasitoids are not adapted to attack it. In fact, we see very few naturally occurring parasitic wasps, common beneficial insects, that are capable of attacking SWD. One way that insects defend themselves against parasitic wasps, is to encapsulate the eggs that female wasps lay inside their body. SWD are better at encapsulating wasp eggs than many other Drosophila species, which means that they are particularly resistant to attack. When eggs are encapsulated, they may be visible externally as black marks when flies emerge as adults.

Male SWD with encapsulated parasitoid egg. Photo: Grant Palmer

This resistance to parasites, coupled with the difficulty in obtaining accurate trapping data when fruit is available, further increases the challenges to managing SWD. We are working with biological control experts at the University of California, Berkeley (Kent Daane) and USDA (Kim Hoelmer) to determine if there are any native wasp able to help control SWD and to determine if there are wasps in areas SWD are native which might be safe to import into the US.

The average number of total (male and female) SWD captured per site per day are presented in the figures below. Trapping began at six blueberry fields on May 11, 2016. Scentry lures were not available until May 17th, so these were deployed at blueberry locations during the second week of monitoring.

YSW refers to traps baited with “yeast/sugar water”, and Scentry refers to traps with Scentry lures.

We are monitoring a total of five blackberry fields, and first checked traps on May 17, 2016. SWD trap captures are generally higher in blackberry fields as compared to blueberry fields.

Data is continually processed and will be updated weekly as it becomes available.

More information

Past insect monitoring reportsEntomology Portal