Unfortunately, box tree moths – an invasive species that will destroy untreated boxwoods – have been found in our neighborhood. Thirteen counties in southeast and central Michigan, including Washtenaw, have been in a boxwood shrubs quarantine zone since 2023. You can read more about the box tree moth here.

If you have any boxwood bushes, MSU Extension recommends that:

“Nursery growers and landscapers may want to consider a precautionary spray program. This could be especially helpful in localities within, and adjacent to, the quarantine area. When spraying preventatively for the box tree moth, MSU Extension recommends two seasonal applications of a labeled pyrethroid product (e.g., bifenthrin) — once in late July and once again in early September. Be sure that the product is labeled for application at that site.

Alternatively, growers and landscapers can also spray a Bacillus thuringiensis (Bt) product once every two weeks starting in late June. Bt is a bacterium that kills insects when ingested. Be sure to use the kurstaki strain, as this is the only one that specifically targets caterpillar larvae. Look for product labels that say Bacillus thuringiensis subsp. kurstaki (Btk).

Homeowners within the quarantine area may want to implement a precautionary management program as well. Please follow the recommendations for nursery growers and landscapers as described above.“

Some neighbors report that the Monterey B.t. spray, available on Amazon, has been working well for weekly applications and after a rain.