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Country Gardens: Bugs in the garden

Here are some pests that have been recently spotted around the area, and Jeffrey Hahn, a University of Minnesota Extension entomologist, explains what to do about them. These will probably show up in your garden year after year, so it pays to know ahead what you can do to help eliminate the problem.


Squash vine borer adults have just been sighted. If you are growing summer squash, winter squash or pumpkins, take the proper precautions to protect your vine crops from this insect. This garden pest less frequently attacks butternut squash, cucumbers and melons. If you are unsure whether squash vine borers are in your area, monitor your garden for their presence.

Set out a yellow pan of water. Yellow is attractive to squash vine borers, and they will fly to and fall into the water. Check these traps at least once a day. Squash vine borer adults are easy to recognize as they are wasp-like and about ½ inch long. They have an orange abdomen with black spots, and the first pair of wings is metallic green while the back pair of wings is clear. These moths are active during the daytime, and you may also observe them when you are in your garden.

Management of squash vine borers is often challenging. There are several steps you can take to try to minimize them, such as planting less attractive crops, making a later, second planting, using row covers (note: do not use row covers if planting vine crops in the same site in consecutive years), and well-timed insecticide treatments.

Another pest people are finding is a curious insect in their gardens and yards now. Grayish black flies, about ¼ inch long, are being found clinging to the leaves and stems of a variety of different plants. Their legs and wings are typically splayed out in odd, unnatural positions. If you watch the fly carefully, you will notice it doesn’t move. That’s because it’s dead – it has been killed by a fungus that is specific to these flies.

This fungus has been particularly common this year due to the abundant rainfall we have experienced throughout much of Minnesota. When seed corn maggot flies become infected with this fungal disease, they usually fly to a plant or other object and climb up. Eventually they die, leaving their legs and wings in whatever position they were in at the time of death. Additionally, their mouthparts are often extended out. In recently infected flies, the abdomen is swollen and whitish, with fungus protruding between the body segments.

When these flies die on a plant that is damaged, it seems reasonable to blame them for this injury. However, seed corn maggot flies do not feed on plants (in fact there are no adult flies in Minnesota that directly feed on plants). They are just a curiosity and should be ignored.


Colorado potato beetle is one you will likely see on the leaves of potato plants. The adults are yellow-orange with 10 black stripes on the wing covers. The larvae are orange, hump-backed  grubs with black spots along the sides. The eggs are yellow ovals that are laid in upright clusters. These beetles not only feed on the potatoes but also tomatoes, eggplant petunias to name a few. You will find leaves defoliated or full of holes. If you have young plants they may die. One of the best ways to curb them is to use row covers and thick and deep straw mulches. Spraying with Beauveria bassiana or spinosad or spraying with neem can help.

Check out the University of Minnesota website: http://www.extension.umn.edu/garden/diagnose/insect/. This site will help you in identifying a pest and also how to diagnose a problem.

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