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Invasive pest that damages boxwood plants found in Michigan

Boxwood comparison.jpg
U.S. Department of Agriculture
Box trees or boxwoods are small, leaved evergreen trees or shrubs generally used in landscaping. On the left is a healthy boxwood and on the right is a boxwood heavily damaged by box tree moth caterpillars.

An invasive pest that attacks a popular yard landscaping shrub has been spotted in Michigan again.

In the spring of 2021, the invasive box tree moth was found in shipments of boxwood shrubs. Now the pest has been spotted again in boxwood plants in the village of Clinton in Lenawee County, about 20 miles southwest of Ann Arbor. The U.S. Department of Agriculture's Animal and Plant Health Inspection Service confirmed the detection.

Boxwood is not native to North America, but it has been used as formal ornamental hedges in civilizations dating back millennia. For growers and tree nurseries, boxwood has significant economic value.

Box tree caterpillar.jpg
Ferenc Lakatos, Soporon University
Box tree moth caterpillars are green and yellow with white, yellow and black stripes and black spots.

The box tree moth, in its caterpillar phase, feeds exclusively on boxwood leaves.

“The box tree moth eggs actually are pale yellow and they're usually laid in groups of five to 20. The caterpillars are green and yellow with white, yellow and black stripes and black spots,” said Jennifer Holton, Communications Director of the Michigan Department of Agriculture and Rural Development.

You’re encouraged to closely examine your boxwood shrubs. You should look for boxwood leaves that look skeletonized or lace-like.

“Young caterpillars feed on the undersides of leaves, giving the leaves kind of a peeled appearance from the top. Older caterpillars consume the entire leaf except for the mid rib, Holton said.

If you think your boxwood is infested, take photos and report to the state what you find here. You're asked to allow agency officials take a look at your boxwood if they suspect an infestation.

To prevent further infestation, pest management officials recommend doing some pruning.

“It's recommended that residents remove their infested branches or if like for really heavy infestations, cut the boxwood from its base. If it's not a heavy infestation, discard all the boxwood debris by double bagging it in the plastic and putting it out with your household trash,” Holton advised.

Even if boxwood is cut down to its base, it should grow back from the roots.

Box tree moth 2.jpg
Szabolcs Safian, University of West Hungary
Box tree moths are generally white with a brown border and a white "comma" on each forewing. However, less often the moth will be entirely brown except for the white forewing spot.

Lester Graham reports for The Environment Report. He has reported on public policy, politics, and issues regarding race and gender inequity. He was previously with The Environment Report at Michigan Radio from 1998-2010.
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