The Gypsy moth infestation has arrived

Q. How do I get rid of these terrible caterpillars eating the leaves off my oak trees? There are thousands of them!

John from Columbiana (and many more)

A. This is the dreaded gypsy moth caterpillar. Valley residents are seeing them in droves, especially in southwest Mahoning and down into Columbiana County.

The gypsy moth is a non-native, invasive pest that feeds on many of our common forest trees as well as certain deciduous and evergreen trees in the landscape. Oaks seem to be their favorite. Caterpillars are grey-black with blue and red dots on their backs and lots of hair. When fully grown, they are 1.5-2.5 inches long. Populations can grow rapidly and defoliate trees. If you have a ton of them now, options are limited and not very effective because the caterpillars are too big for the naturally occurring bacterium, Bacillus thuringiensis (Bt), this late in the game. Find a list of options on the fact sheet below.

Our part of Ohio is generally infested. Thus, the Ohio Department of Agriculture will engage in gypsy moth suppression by spraying Bt at the request of property owners at a cost share rate and on blocks of more than 50 acres. But they don’t spray for individual homeowners. Contact ODA for details and to report your location and population of caterpillars at http://go.osu.edu/odamoths or 1-800-282-1955. Click Suppression Program,” on the website, for criteria and applications. The deadline is Sept. 1 for 2015.

The caterpillars will enter the pupal stage soon, so we’ll see the moths fly in just a few weeks. There are no real control options for the moths. Pheromone traps are commercially available, though. Moths will be lured to those instead of decks and patios. But if the pheromone is touched, the person becomes attractive to the moths, so be careful. In preparation for their return next spring, Bt may be an option for some. Homeowners could plan sprays based on our OSU phenology calendar and spray at the second instar. In general, outbreaks rarely last more than two to three years. Our experts received photos this year showing the natural virus and the fungus are working.

If your trees are defoliated, be sure the affected trees are irrigated to assist them in putting out that second set of leaves.

Eric Barrett is OSU Ext. educator for agriculture and natural resources in Mahoning County. Amy Stone, Dr. Dan Herms and Dr. Dave Shetlar contributed to this answer. Call the office hot line at 330-533-5538 from 9 a.m. to noon Mondays and Thursdays to submit your questions.