New Jersey forestland damaged by gypsy moths has increased in the number of acres for the first time since 2008, and state officials are trying to figure out why.

The 2,887 acres of forest defoliated this year are minuscule compared with the 800,000 acres the state Department of Environmental Protection said were damaged by the insect at the height of the state's gypsy moth infestation, in 1981. Still, this year's defoliation represents an increase of more than 170 percent from the 1,068 acres that were damaged by gypsy moths in 2012.

Most of the damage occurred in North Jersey, according to a state Department of Agriculture aerial survey of New Jersey done in late June and early July.

Damage in South Jersey was considered minimal and included 191 acres in Ocean County, 144 acres in Atlantic County and 17 acres in Cumberland County, the survey shows. That damage occurred mostly in deep woods, state agriculture officials said.

Now, agriculture officials will try to determine why the damage increased from last year. Part of the reason might simply be the cyclical nature of the gypsy moth population, they said.

Inspectors will perform ground surveys of the damaged areas beginning in late August or early September, with those surveys extending into December, said Joe Zoltowski, chief of the state Agriculture Department's Bureau of Plant, Pest and Disease Control. Among the things inspectors will look for are signs of gypsy moth egg masses, he said.

"They lay a lot of eggs, with eggs inside eggs," he said.

State agriculture officials said a single egg mass can contain as many as 1,000 eggs.

Agriculture officials also will look for a special fungus that has helped control the gypsy moth population for decades, Zoltowski said. The fungus thrives in the kind of wet weather the state experienced this year, he said. It works by attaching itself to gypsy moth hair, then essentially grows into and helps kill the insect, he said. The impact of the fungus on the gypsy moths will not be known until later this year, he said.

Overall findings could result in the state resuming some kind of gypsy moth spray program in 2014, Zoltowski said.

The state last sprayed for gypsy moths in 2011, and that involved about 275 acres in two Camden County municipalities. State agriculture officials would not say whether the lack of a spray program may have contributed to this year's increased gypsy moth damage. There was no spray program this year, because the gypsy moth population was considered to be a small, they said.

To qualify for the state's gypsy moth spray program, a residential or recreational forest must have an average of more than 500 egg masses per acre and cover at least 50 acres.

State Secretary of Agriculture Douglas Fisher said the state must "continue intense surveillance as well as treatment to suppress this damaging insect."

"We will continue to partner with the state Department of Environmental Protection, counties and municipalities to protect our precious forested areas from being devastated by gypsy moth caterpillars," he said.

The gypsy moth is native to Europe and was introduced in the United State in Massachusetts in 1869 by a French botanist trying to develop the silkworm industry. Some of the insects eventually escaped from his laboratory. They colonized and spread - gypsy moths can travel about 13 miles in a year - and are now found in about 19 states.

The insect pest feeds on hundreds of varieties of trees and shrubs. The moth prefers the oak as a host tree.

This year's annual aerial survey revealed gypsy moth-caused defoliation in 51 municipalities in Atlantic, Bergen, Burlington, Camden, Cumberland, Essex, Gloucester, Hunterdon, Mercer, Middlesex, Monmouth, Morris, Passaic, Somerset, Sussex and Warren counties. Suffering the most damage were the Passaic County municipalities of Bloomingdale and West Milford Township.

Zoltowski said North Jersey was hit harder than the rest of the state because of gypsy moths blown into the area by winds coming from Pennsylvania and New York.

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