Hardwood trees such as birch, maple or oak are in danger because of a little bug—the spongy moth—native to parts in Europe, but has been in the U.S. for over 100 years.
The spongy moth is making its appearance this month in southeast Wisconsin, and in its caterpillar stages, it's known to eat away at the leaves of our area's trees. If the spongy moth isn't dealt with, it could damage our treescapes.
PJ Liesch is an extension entomologist and director of the Insect Diagnostic Lab at UW-Madison and shares what we can do to stop their population from growing.
Liesch explains, "In 2022, we've had lots of reports of tree damage, including defoliation due to these insects. The caterpillars can be pretty large, up to about two and a half inches long."
The spongy moth was brought to North America from Europe in 1869 by a man who wanted to breed a hardy silkworm. But moths escaped his Massachusetts home, and by 1889, the spongy moth started to defoliate trees in the area. The bug arrived in southeast Wisconsin in the 1980s.
According to Liesch, this year there is an increase of the spongy moth population because of last year's dryer conditions.
The spongy moth doesn't have many natural predators. But a fungus can kill off the invasive moth at its caterpillar stage, which is best done under rainy or wet conditions. So, Leisch is hopeful the rain we've been seeing will help.
Liesch says that if you have an oak tree in your yard that is in healthy condition, it can withstand defoliation."[Oak trees] have energy reserves, those trees can put out another batch of leaves, and will leaf out again," he says.
He cautions if it happens repeatedly becuase it will create secondary problems.
Liesch recommends tying burlap around the tree trunk to prevent the moth in its caterpillar stage from nesting in hardwood trees. And to be careful of transporting firewood across the state, where sometimes spongy moth eggs can hide.
You can find more detailed information on the spongy moth here.
