Spotted Wing Drosophila Monitoring Report June 10, 2016

— Written By Grant Palmer and last updated by

With summer, has come earlier spotted wing drosophila (SWD) pressure than in recent years. As a result of this early pressure, growers are having to engage in proactive management. Several blackberry research sites have had a growing population of spotted wing over the last couple weeks.

However as these sites take management action, we see substantial drops in the fly capture numbers. This could mean that the populations of SWD are being successfully reduced by insecticides or other management efforts, but that is not the only possibility. Population dips have also corresponded with fruit ripening, and thus increased vulnerability of the fruit; in particular in blackberries. Previous research in our group has suggested that SWD could be significantly more attracted to the available berries as a site for ovisposition than to fermentation volatiles in traps.

Syrphid fly: a common pollinator seen in blackberry fields that could be harmed by earlier pesticide spraying for SWD.

Syrphid flies are common pollinators seen in blackberry fields. Blackberries often have open flowers and harvestable fruit present at the same time. Photo: Grant Palmer

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.

This is a graph depicting number of SWD captured on a total/SWD per day basis in YSW traps.

This is a graph depicting the number of SWD captured on a total/SWD per day basis caught in Scentry bait traps.

We are monitoring a total of five blackberry fields, and first checked traps on May 17, 2016.

This is a graph depicting number of SWD captured on a total/SWD per day basis in YSW traps

This is a graph depicting number of SWD captured on a total/SWD per day basis in Scentry bait traps.

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

SWD trap captures are generally lower in blueberry fields than in blackberry fields. Decreases in recent trap captures corresponds with fruit ripening and field spraying. It will be interesting to see whether Lincoln 3 YSW drops correspondingly with its Scentry counterpart.