The good news is box tree moths only eat boxwoods; the bad news is they'll be waking up from winter soon with voracious appetites. The Ohio Department of Agriculture this week expanded the quarantine zone to seven counties, meaning people shouldn't transport the shrubs in Butler, Clermont, Greene, Hamilton, Miami, Montgomery, and Warren counties.
Box tree moths were first discovered in Ohio near the border between Hamilton and Clermont counties in June 2023. The goal is to keep them from expanding further in Ohio, and to keep them out of Kentucky and Indiana all together.
"What we're looking for are these green and yellow striped caterpillars that are only going to be found on boxwoods. They don't eat anything else, so you don't need to worry about them on your dogwoods or on anything else in your landscaping," says Joe Boggs, assistant professor with the Ohio State University Hamilton County Extension. "At this time of the year, they're in a stage where they're going to be hard to detect. ... As temperatures warm, probably sometime towards the end of March [or] first of April, we'll start seeing those caterpillars emerge. They're going to still be small, but because they've spent the winter starving, they're going to feed very, very voraciously once they do emerge."
For now, you may be able to spot them wrapped up in their winter silk nests, tucked deep inside your boxwood shrubs. The caterpillars are green and yellow with white, yellow, and black stripes and black spots. The adult moths are nocturnal and have white, slightly iridescent wings, with an irregular thick brown border.
You'll find lots of pictures of the various life stages and shrub damage in the slideshow above.
The moths are native to East Asia. Signs of damage include chewed, cut, or missing leaves, yellowing or brown leaves, white webbing, and green-black excrement on or around the plant.
Smoosh or spray?
Why not both?
"Well you could smoosh them," Boggs concedes. "That's kind of fun, right? That's very satisfying. But there's probably more there."
If you find box tree moths, eggs, caterpillars, or pupae, he recommends using a biorational insecticide (relatively non-toxic with few environmental side effects).
You can also use a standard insecticide that says it treats caterpillars. Boggs says you should not use insecticides as a preventive method because you will likely kill other good bugs your plants and the soil need. Plus, he says, it's a waste of money and product.
The OSU Extension office offers three fact sheets about the life span, effects, and ways to treat box tree moths:
How to report box tree moths
"To our knowledge... if you're in Northern Kentucky, it's so important to report it because we don't know that it's there yet. We don't know that it's in Indiana yet," Boggs tells WVXU. "So while we do know it's in Ohio, it's important to report it [especially] if it's away from what we call the hot spot."
That means if you live on the outer edges of the quarantine zone, or near the state borders. The current "hot spots" for the pests are Loveland and Kettering, Boggs says.
In Ohio: Report suspected box tree moth sightings through ODA's reporting tool.
In Indiana: Contact DEPP@dnr.IN.gov or your local nursery inspector to report suspicious finds.
In Kentucky: Contact reportapest@uky.edu or your local UK extension office if you spot damage or capture a specimen.
Pruning may help
Boggs says a nice thing about boxwoods is that they can be cut back, as they respond well to rejuvenation pruning.
"If you've had damage from last year and it's lingering, cutting those boxwoods back right now will allow them to regrow, and it's amazing how fast they do regrow," he says.
If you discover box tree moths later in the summer, you can use a treatment method, then as the winter season approaches, do some serious pruning.
"When those boxwoods go to sleep for the winter, you can cut them back. Leave maybe a foot or two of stems. And the following spring, the boxwoods will grow at a phenomenal rate."
He notes the moths won't wipe out the plants all together, so you don't need to yank out the plants and find something else, just prune them and let them grow back healthier.
"A lot of people don't realize this, but boxwoods do bloom, and they're very important for pollinators early in the season," he adds. "They do provide a lot of service beyond looking good in landscaping, also, they're very good for pollinators."
