The Michigan Department of Agriculture and Rural Development (MDARD) and the United States Department of Agriculture (USDA) recently reported the presence of box tree moths in Lapeer County.
Although this invasive pest is not a threat to Michigan’s natural resources, it can lead to significant defoliation and death of ornamental boxwood. The new population of box tree moth was discovered through monitoring efforts in collaboration with the USDA. MDARD has been conducting statewide trapping for the pest, while the USDA has focused on trapping around the perimeter of the other 12 counties currently under quarantine to track the spread of this pest.
Last year, MDARD implemented a box tree moth interior quarantine, which now encompasses 12 counties in Southeastern Michigan, including St. Clair County. MDARD is currently working to update the quarantine to include Lapeer County, making it the 13th county impacted by BTM.
Box tree moths may not be easily recognized at the beginning of an infestation because young caterpillars hide among twigs and leaves. Box tree moth caterpillars are green and yellow with white, yellow, and black stripes and black spots. Adults have white wings with dark brown borders and a distinctive white dot or mark in the middle of each forewing.
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.
If you suspect you have found an infestation and are outside of the quarantine area, please take photographs and report it at www.Michigan.gov/ReportBTM.
After MDARD officials have confirmed a suspected case, residents 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. Some municipalities or trash vendors may have restrictions surrounding plant material disposal, so please check with your local waste management entity for guidance.
For more information about pest treatment and a list of insecticides known to be effective against destructive caterpillars, view the Michigan State University Insecticide Options for Box Tree Moth Management. Additional information about box tree moths can be found at www.michigan.gov/invasives.
