Over the summer our raspberries got infested with drosophila, like so many in...

Asked November 17, 2015, 11:22 AM EST

Over the summer our raspberries got infested with drosophila, like so many in the Twin Cities' urban gardens. The raspberries have been cut back and our fingers are crossed for next year. However, now the drosophila have moved into the compost, about 20' away from the berry canes in our small yard. We have a closed bin, one of the rotatable black plastic barrel ones with air holes on the ends, and use it for both household and yard waste - although we did not, of course, put any of the raspberry waste directly in there. Is there any hope for our compost? If we need to dispose of it and start over, what is the best way to do that? Thank you for your help!

Hennepin County Minnesota

1 Response

If the compost material you are using from your enclosed rotating black plastic barrel is infested with small flies, then the material was not 'cooked' long enough to obtain a heat sufficient to kill all flies and their larvae & eggs. This can happen with a 'backyard' composter system, because internal temperatures rarely get about 120oF. Since winter months are approaching, you would be wise to remove all material from the composter and spread it out, no more than a foot thick, on the ground - allowing the winter cold temperatures to kill all stages of the drosohila. If your ground is not frozen, dig a trench about a foot deep and place the compost material in this ... a type of 'trench' composting recommended for gardens. Clean-out the inside of the composter with hot water and let it air dry for about a week before refilling. Since your raspberry plants were infested with these flies, they are harboring in more than this area of your yard. Treat the raspberry plants with a recommended insecticide according to the label direction. Contact your local cooperative extension office (University of Minnesota-Extension office, 479 Prairie Center Dr, Ste 2, Eden Prairie MN 55344-5378, (612) 596-2110 (phone), (612) 466-9947 (fax), mnext-hennepin@umn.edu) for help with the raspberry plants. ~DOT