Bad news for boxwood: box tree moth has arrived in WNY

egg mass on boxwood leaf
Has your boxwood been infested with the box tree moth? Look for egg masses on the underside of the leaf. Photo courtesy Walter Schön, www.schmetterling-raupe.de/art/perspectalis.htm

by Connie Oswald Stofko

An invasive moth that damages and can kill boxwoods has arrived in Western New York.

The box tree moth has been identified in Niagara County, said John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County.

My sister in Cheektowaga has noticed damage to boxwoods in her area. That was probably caused by the box tree moth, too, Farfaglia said.

This invasive pest “is expected to spread,” he said. If you haven’t seen it in your area yet, “expect it to show up in the coming year.”

The damage caused to boxwoods will be a problem for many gardeners because the boxwood is one of the few evergreens that are deer resistant, Farfaglia noted.

“And people who have boxwoods, have a lot of them,” he said, noting that gardeners often use them for long hedges. “It’s an important plant for the nursery industry.”

The box tree moth has been in Ontario since 2018, according to PennState Extension. The insects there had two generations per year: one cluster from late June into July and again in late August through September. (In other climates, the pests can have as many as five generations per year.)

Boxwood damage: what you can do

Examine your boxwoods

Look for egg masses on the underside of the boxwood leaves, caterpillars and webbing, pupae (cocoons) and adult moths. See photos and more information here from the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

Contact Cornell Cooperative Extension

If you believe you have damage from the box tree moth, contact the Cornell Cooperative Extension Service in your county.

If you live in Niagara County, you don’t have to call; they already know the box tree moth is there.

Treat your boxwoods

For home gardeners, Farfaglia said there are three kinds of pesticides available:

  • Spinosad. This is a natural substance made by a soil bacterium that can be toxic to insects, according to the National Pesticide Information Center. One brand name you might see for gardeners that uses this ingredient is Captain Jack’s Deadbug Brew, Farfaglia said.
  • Bt or Bacillus thuringiensis. Bt is a microbe naturally found in soil, according to the National Pesticide Information Center. It makes proteins that are toxic to immature insects (larvae). One brand name you might see for gardeners is DiPel, Farfaglia said.
  • Sevin. It contains carbaryl. Farfaglia noted that it poses problems with bees, so you must be very careful when using this around flowering plants.

There are other pesticides that can be used by licensed pesticide applicators. If you have significant plantings of boxwood, you might want to call a professional, he said.

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