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Insects - Spotted Wing Drosophila Update

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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 (Aug 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 Co.). Thirty wild blueberry fields are being monitored by the Maine Dept. 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 upon 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 persistance of kill (residual in table) of the material (see list of insecticides below).

Liberal approach: Coninue to trap after you catch your first fly and when fly numbers START to increase from 1 fly in a trap to 3, 5, 10, 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 1-2 days after a confirmed trap capture may allow you to harvest the crop with out making an application if you feel that you can get the berries out of the field immediately.

Currently Available Products for SWD Control:

Chemical Class Active Ingredient Trade Name PHI Days of Residual Comments MRL for Canada (Yes/No)
Organophosphate malathion Malathion 1 5-7   Yes
  phosmet Imidan 3 7 Long PHI Yes
Pyrethroid zeta-cypermethrin Mustang-Max 1 7   No
  bifenthrin Brigade 1 7   No
  zeta-cypermethrin+bifenthrin Hero 1 7   No
  esfenvalerate Asana 14 7 Very long PHI No
  fenpropathrin Danitol 3 7 Long PHI Yes
Carbamate methomyl Lannate 3 3-5 Short lives, long PHI Yes
  carbaryl Sevin 7 5-7 Long PHI, Not as effective as others Yes
Spinosyn spinetoram Delegate 3 7 Long PHI Yes
  spinosad Entrust 3 3-5 Short lived, Long PHI Yes
Pyrethrum pyrethrum Pyganic 0.5 2-3 Very short lived Yes

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

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