Environment Task Force Newsletter
Ohio State University Extension
Spring, 1998, v1 #4

Gypsy Moth Numbers Dramatically Down

Allen Baumgard, Ohio Department of Agriculture Gypsy Moth Program Manager

In 1997, Ohio's gyspy moth treatment acreage decreased for the first time since we began suppression projects in 1990. We had a total of 18,517 acres of suppression and 3 acres of eradication.

Steps to control the gypsy moth and its caterpillars (above) have made great strides in the past two years.

As in other states, Entomaphoga maimaiga, "the Gypsy Moth Fungus," caused large population crashes in many of our gypsy moth populations in 1996. We saw similar results in 1997 due to the cool, moist spring. The fungus, which grows better in wet conditions, releases spores in the spring that infect and kill gypsy moth larvae or caterpillars.

Fungus, weather play key roles

Toledo was inoculated with the fungus and suspect caterpillars have been observed. The fungus seems to be appearing everywhere we have gypsy moths. While this may not be the silver bullet, it can cause population crashes when weather conditions are right.

In all, 24 Ohio counties are under Gypsy Moth quarantine as of January 1, 1998.

Hot spots still exist

Even with these crashes, we still find problem hot spots. The egg masses we are seeing are very large and healthy.

Our defoliation survey results showed a dramatic decline in acreage in 1997. We expected this due to the big fungus-related population crash in 1996. Our totals for 1997 were only 4,852 defoliated acres, compared with more than 49,000 acres 1996. All gypsy moth states have seen this type of decline except Michigan.

We continue to use pheromone traps to trap more than half the state for moths. With 1997's cold spring, insect development was much slower than normal. Moth flight didn't start until July 18, a good 10 days to two weeks later than usual. We placed 8,451 traps out, catching 41,632 moths.

Some counties experiencing bigger problems

We saw a very large increase in catches in the northwestern part of Ohio, an area where we usually catch very little. We attribute this to some sort of a blow-in from a storm system. Indiana saw a similar phenomenon. Some of these counties that caught less than 10 moths in 1996 caught several hundred in 1997. This phenomenon makes it very difficult to isolate new infestations.

Editor's Note: The gypsy moth is one of the most destructive insect pests threatening the forests and ornamental plants of Ohio. The insect feeds on the leaves of trees and can completely defoliate large areas of forests.

Native to Europe, Asia, and North Africa, the gypsy moth was established in North America in 1869 in Massachusetts and has gradually spread westward. In 1987, as the gypsy moth continued its march into Ohio from Pennsylvania, the northeastern part of the state was quarantined to prevent the artificial spread of this pest. Ohio gypsy moth populations first reached defoliating levels in 1990.