Three Bad Bugs in Northern Gardens

At the recent Upper Midwest Master Gardener conference at the Minnesota Landscape Arboretum, entomologist Jeff Hahn led a session called “Watch out for These Insects.” In it, he highlighted the top six insects that threaten gardens in the Upper Midwest. Here are three of them — tomorrow we’ll highlight three more.

Some of these guys you have seen; others are on their way.

brown marmorated stink bug

USDA image

Brown Marmorated Stink Bugs: While not a pest in northern gardens yet, Hahn and other entomologists expect that the BMSB will be here before long. It’s been discovered in seven Minnesota counties so far, but in very, very small numbers. Originally from China, BMSBs feed on more than 200 plants, including trees, shrubs, fruits and vegetables. Brown Marmorated Stink Bugs look a lot like our native stink bugs, but there are two distinctive things to look for: BMSBs have banded antennae and legs and greenish gold flecks on their undersides. If you capture one, contact the Minnesota Department of Agriculture so it can be positively identified. For more information on stink bugs, see the article in the July/August issue of Northern Gardener.

Earwigs: While they can cause a lot of damage, earwigs are fascinating insects. Unlike most members of the bug world, earwig females will guard their eggs and care for the young. Unfortunately, the earwigs feed on leaves and blossoms of plants and enter homes looking for food and warm spaces. Sometimes, they come in in very large numbers, similar to boxelder bugs or lady beetles. Earwigs like to hide in warm moist places, so to deter them clean up debris, keep mulch layers thin and do not water everyday. To keep them out of your house, be sure to seal any cracks or spaces. If the problem gets very bad, you may need to use insecticides. The U of M has a good fact sheet on earwig control.

Eastern tent caterpillar nest

Eastern tent caterpillars return to the nest.

Tent caterpillars. There are two kinds of tent caterpillars and only one of them actually builds a tent. The eastern tent caterpillar has a blue and black body with white or yellow stripes down the back. These caterpillars build nests in fruit trees in late spring. They can seriously defoliate a tree. Healthy trees can endure this without severe damage, but a young or unhealthy tree may be killed by the caterpillars. Forest tent caterpillars are sometimes mistakenly called army worms. They do not build a true tent, but the larvae live under a silken mat that looks tentlike. They also can defoliate trees, but rarely kill a mature tree. They won’t harm humans or pets either, but there is a significant ick factor when lots of caterpillars are moving on the outside of buildings looking for places to build cocoons. Physical removal of nests is probably the best control for tent caterpillars.

Tomorrow: Three more bad bugs.

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