Invasive gypsy moths on the rise in Michigan

Leonard N. Fleming
The Detroit News
A gypsy moth.

State officials have expressed concern about an influx of invasive gypsy moths in southern Michigan, saying the insects can harm native species and ecosystems.

DNR officials said a large population growth of the moths in 2018 is spurring more caterpillars to hatch this spring.

The largest defoliation is in Washtenaw, Barry and Ionia counties, the Michigan Department of Natural Resources said. The moths also are causing headaches in other areas of the Lower Peninsula.

Heavy defoliation likely will become visible within the next few weeks and persist through mid-July, the DNR said.

“Gypsy moths rarely kill trees in Michigan,” said James Wieferich, DNR forest health specialist. “Only stressed trees suffering from problems like drought, old age or root damage are at high risk. In most cases, gypsy moth caterpillars are more of a nuisance in residential areas than in the woods.”

First discovered in 1954 in Michigan, gypsy moth caterpillars are hairy and grow up to 2-inches long with a pattern of dark red and blue spots. Male moths are dark in color and fly, while females are white and black with wavy markings and do not fly.

Mature trees, DNR officials said, can tolerate gypsy moth defoliation with minimal problems, but those that aren't as healthy coupled with years of mass defoliation can take a toll.

The DNR said in its caterpillar stage, the insect caused "widespread defoliation," which destroyed leaves from the 1980s to early 1990s. Up to a million acres were defoliated in some years, said Scott Lint, DNR forest health specialist.

State officials say to reduce the impact of gypsy moths, monitor the health of trees.

"Water trees regularly and avoid damaging the roots and bark," Wieferich said. "That goes a long way in helping trees fend off the effects of defoliation."

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