Forest Tent Caterpillars Causing Concern

Minnesota Department of Natural Resources officials are concerned about outbreaks of forest tent caterpillars in northern Minnesota this summer.

Forest Tent Caterpillar image courtesy MN DNR

The Minnesota DNR offered THIS media release on the issue.

DNR officials will soon be flying an aerial detection survey across the state to pinpoint where defoliation from forest tent caterpillars has occurred this spring and to measure the severity of the outbreaks.  Homeowners and foresters have noted an uptick in the forest tent caterpillar population in Minnesota’s northern counties.

Forest tent caterpillars, often referred to as “army worms,” are a native defoliator of a wide variety of hardwood trees and shrubs. Their range in North America extends from coast to coast and from the tree line in Canada to the southern states.  Defoliation typically starts in late May in northern Minnesota and is normally finished by mid to late June.

“While the caterpillars don’t cause a health risk to humans, the presence of hundreds (or thousands) of them can be a real headache,” Jana Albers, DNR forest health specialist in Grand Rapids said. “The effects of defoliation on shade trees, ornamental plantings and gardens can also be of concern to the homeowner.”

Since it is a native insect, native parasites and predators ultimately push an outbreak to a crashing halt, said Albers. Normally there is little effect on the defoliated trees; reduced growth is the main effect. However, if trees are under stress from prolonged drought or have root system damage, defoliation can cause other pests to weaken or kill those trees.

The DNR provides technical advice to homeowners and land owners interested in treating their vegetation. More information about the biology and management tips for forest tent caterpillars can be found HERE.

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