More gypsy moths may threaten trees

Scientists and forest officials are reporting a sudden increase in egg clusters, which will hatch in the spring

October 21, 2005|By DORCAS TAYLOR | DORCAS TAYLOR,CAPITAL NEWS SERVICE

A sudden resurgence of gypsy moth egg clusters in Garrett County, combined with this year's drought, could mean trouble for the state's forests next spring.

Bob Tichenor, the chief of forest pest management at the Maryland Department of Agriculture, said forest entomologists tell him the tan groupings are "some of the largest egg masses we've ever seen."

Some areas of Garrett County are seeing more than 500 clusters per acre, with the masses measuring up to 1.5 inches and holding 1,200 eggs, Tichenor said. Those preliminary figures fall in the middle of a per-acre scale the department uses to prioritize spring spraying.

Clusters in Anne Arundel County, comparatively, have been very low this year and last year, he said. Because surges are usually cyclical, peaking every five to seven years in Maryland, Tichenor said the numbers will likely remain low in Anne Arundel County for several years. The last peaks were in 2000 and 2001 and from 1990 through 1992.

Entomologists began looking for the bugs in state forests in August as a part of the state's annual survey, said Sue duPont, Maryland's agriculture spokeswoman. The moths typically lay their eggs at the end of July.

The insect's reappearance does not bode well for trees this spring, insect and forestry experts said.

Trees already stressed because of the drought will be further strained when the moths hatch as caterpillars in April, said Michael Raupp, a professor of entomology at the University of Maryland. The caterpillars consume large quantities of the trees' leaves, signaling the plant to dip into its stockpiled nutrients.

Once the tree uses up its reserves, Raupp said, it becomes vulnerable to other insect predators.

Among those predators is the two-lined chestnut borer, which tops Raupp's list of concerns.

"This guy is just waiting for a tree to be in trouble," Raupp said. "They're going to attack the tree by the hundreds" when a vulnerable plant is discovered.

Many trees damaged by an ice storm a few years ago are in the same area as the increased moth populations, Tichenor said. Those trees are just starting to rebound.

During normal weather cycles, oaks and maples can withstand defoliation of up to 30 percent in the early spring, Raupp said. But leaf loss beyond that puts the plants in danger because they are unable to store necessary starches to replace leaves.

Although gypsy moths will eat up to 100 different kinds of plants, he said, black and red oaks are on the insect's short list of favorites.

So far, field officers have found the largest number of clusters north of the town of Oakland, Tichenor said, along the county's oak-canopied ridges.

There are places where the groupings are very close together, said Bob Webster, western Maryland's regional forester.

"The egg masses are about as big as my thumb, and the bigger they are, generally speaking, the healthier they are," Webster said.

Visible from the ground, the eggs are usually grouped along trees' bark and limbs. They can also be found in stacks of firewood, which worries Raupp because people could inadvertently pick up the infested wood and spread the insects to other areas.

The larvae disperse when they release a silky thread and get carried away by the wind to nearby trees, but that is usually as far as they get, Raupp said. Female moths do not fly.

Forests likely will be sprayed with insecticides next spring to kill the insects, duPont said. In 2003, the state sprayed 14,000 acres, and in 2002, more than 39,000 acres were sprayed in 14 counties and in Baltimore.

Maryland's moth infestation peaked in 1990, when the department sprayed 187,723 acres and the moths defoliated an additional 133,000 unsprayed acres. Tichenor said the department had to prioritize areas. That same year was Garrett County's worst, with 36,705 of its trees defoliated by the moths.

Tichenor wouldn't compare what happened 15 years ago with what could happen next spring but said potentially large areas are at risk of defoliation.

Nature provides another line of attack against the bugs. The fungus Entomophaga maimaiga, kills the insects and reduced the number of moths in Maryland in the mid-1990s.

The disease makes its way into the gypsy moth population through young caterpillars, Tichenor said, when spores along the forest floor infect them. When those caterpillars die, they produce another disease that kills older caterpillars unaffected by the spores. The disease needs moist conditions to thrive.

But even if the spring weather is cool and wet, Tichenor said, it takes time for the caterpillars to spread the disease to older adults, which already have eaten tree leaves. Therefore, spraying begins while the caterpillars, which emerge in late April and early May, are still young.

Gypsy moths have been a constant presence in the state since they appeared more than two decades ago, devastating trees in state parks and residential neighborhoods.

Surveying will continue until all of the masses are spotted, duPont said. The hope is to finish by Thanksgiving, but work could extend into the winter.

There are no estimates yet on how much land could be sprayed next year, duPont said.

Dorcas Taylor writes for the Capital News Service.

Sun reporter Bradley Olson contributed to this article.

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