8.13.12 URGENT: Spotted Wing Drosophila Update

By Frank Drummond

The state of Maine has secured a Section 18 “Crisis Exemption” registration for a higher rate of Malathion 8Fl that is more effective for the SWD than the lower rate on the existing label. This higher rate is in EFFECT on August 13 and only lasts for 15 days (August 13-28). If you decide to use this material at the higher rate very strict reporting is required by the US EPA. The forms for reporting can be acquired from the Maine Board of Pesticide Control.

Last week (August 10) spotted wing drosophila (SWD) showed up in a few more blueberry fields. We have found adult male flies in traps in TWO fields in Franklin (Hancock Co.), one field in Surrey, two fields in Ellsworth, one field in Harrington, and one field in Jonesboro. I (Frank Drummond) have also confirmed trapping of adult flies from several fields in Deblois (Washington County). Thirty wild blueberry fields are being monitored by the Maine Department of Agriculture and the University of Maine and many additional fields are being monitored by growers and so far the picture is that SWD appears very spotty across our blueberry growing areas. But, please be vigilant and continue to trap for SWD in fields that you have not harvested yet.

What to do if you do find flies? Well, there are several approaches, NONE of which are based on experimental evidence from wild blueberry research in Maine.

Conservative and most safe approach: as soon as 1 fly is trapped and confirmed apply a suitable insecticide at an interval that reflects the average persistence of kill (residual in the table) of the material (see the list of insecticides below).

Liberal approach: Continue to trap after you catch your first fly and when fly numbers START to increase from one fly in a trap to three, five, ten, etc., then consider applying an insecticide.

Whatever strategy you pick, consider the following before applying an insecticide:

  1. If you sell to a processor, check with them to see what material can be used.
  2. Make sure that the PHI for the material that you choose is in accordance with your harvest schedule.
  3. A PLANNED harvest one to two days after a confirmed trap capture may allow you to harvest the crop without making an application if you feel that you can get the berries out of the field immediately.