LANSING, Mich. — The Michigan Department of Agriculture and Rural Development (MDARD) announced it is implementing a new quarantine for the invasive box tree moth (Cydalima perspectalis) after multiple detections of the invasive species were found in Lenawee county in 2022. Although not a threat to Michigan’s natural resources, this invasive pest can lead to significant defoliation and death of ornamental boxwood. The quarantine went into effect on April 10.  

The quarantined area includes the entire counties of Lenawee and Washtenaw, the county of Monroe west of US-23 and north of River Raisin, and the county of Jackson south of 1-94 and east of US-127. Under the quarantine, the whole plant, plant parts, and nursery stock of the genus Buxus, including all living and dead material, cannot be moved outside of the quarantined area.

“Ornamental boxwood plants are economically significant for Michigan’s green industry,” said Mike Philip, MDARD’s Pesticide and Plant Pest Management Division Director. “By enacting this regional quarantine, we hope to prevent the spread of box tree moth across the state, facilitate safe trade of plant materials, and minimize the impact on other nurseries, greenhouses, and retailers outside of the quarantined area.”

Box tree moth caterpillars are green and yellow with white, yellow, and black stripes and black spots. The caterpillars feed only on boxwood making them easy to spot. Adult box tree moth has two color forms. The most common form has white wings with dark brown borders, while the dark form has solid brown wings with a white streak or spot on each forewing. Both forms have a distinctive white dot or mark in the middle of each forewing.

Box tree moth may not be easily recognized at the beginning of an infestation, because young caterpillars hide among twigs and leaves. Signs of infestation include chewed, cut, or missing leaves, yellowing or brown leaves, white webbing, and green-black excrement on or around the plant. Larvae skeletonize the leaves and feed on the undersides, causing defoliation and dryness and eventually leading to the plant’s death.

“We’re asking residents within the quarantine area to examine their boxwood for symptoms of box tree moth. Suspected cases can be reported online at www.Michigan.gov/ReportBTM,” added Philip. 

Residents with confirmed cases are advised to remove infested branches or, for heavy infestations, cut the boxwood from its base (it should grow back from its roots). All boxwood debris should be double bagged in plastic and discarded with household trash after confirming with the local municipality or trash vendor whether these materials can be collected. For more information, and a list of insecticides known to be effective against destructive caterpillars, go to www.aphis.usda.gov/planthealth/box-tree-moth.