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The amount of tree damage caused by gypsy moth caterpillars this spring decreased for the first time since 2003, state Agriculture Secretary Douglas H. Fisher said Wednesday.

The state Department of Agriculture’s annual statewide gypsy moth aerial defoliation survey showed 91,890 acres of trees experienced some level of leaf loss this year, as compared with 339,240 acres last year.

“The gypsy moth population reached its peak in 2008 and through a combination of regular life cycle drop-off, beneficial fungus and natural predator increases combined with our aggressive spray program, we are pleased to see a downturn,” Fisher said. “Any amount of tree damage by these destructive caterpillars is significant, so the Department of Agriculture will continue to closely monitor, survey and spray, where necessary, to control the spread of the gypsy moth in the future.”

In addition, there were increased established parasite levels, which are helping the gypsy moth population to collapse. Those parasites were released by the department decades ago to fight the gypsy moth.

A total of 184 towns in 19 counties experienced defoliation this year. Although that was an increase over last year’s total of 134 towns and 17 counties, most counties had significant decreases in the amount of tree damage.

Although Ocean County experienced the most acres of trees defoliated this year, with 16,293 acres, it still had a substantial decrease from last year, when 44,205 acres of trees were damaged. Jackson Township saw a large decrease from 22,384 to 4,927 acres.

The survey showed that gypsy moth populations have spread to certain areas of the state, due to natural and wind-borne movement. In high populations, gypsy moths can blow 15 miles during storms, spreading into untreated areas.

Seven counties had increased defoliation from last year:

Cumberland had the third highest level of defoliation in the state with 13,828 acres of trees damaged. That compares with last year when 3,608 acres were defoliated. The town with the most defoliated acres, Downe Township with 6,080 acres, is in Cumberland.

Morris did not have any defoliation last year. Hanover Township was the only town that participated in the aerial spray program.

Hanover did not experience any defoliation this year but 19 municipalities had 7,737 acres defoliated.

Mercer did not participate in the spray program this year. It saw 1,839 acres defoliated in 7 towns, as compared to 127 acres in 2 towns last year.

Bergen did not have any defoliation last year and was not part of this year’s aerial spray program, but lost 104 acres in 6 towns.

In Middlesex, 11 towns experienced 3,299 acres of defoliation this year. Last year, 9 towns had 2,507 acres of trees damaged.

Essex had an increase from last year, with 759 acres in 7 towns defoliated this year and 127 acres in 2 towns last year. Livingston was the only town to participate in this year’s spray program.

Salem had a slight increase this year, with 418 acres damaged in 2 towns and 326 acres in 3 towns last year.

The 2009 Gypsy Moth Aerial Spray program included 15 counties, 55 municipalities and 11 agencies with spraying on 35,816 acres of wooded residential and parkland, wooded areas along the Garden State Parkway and areas of the Earle Naval Weapons Station.

This year, the U.S. Forest Service provided $1,480,472 in cost reimbursement funds to towns participating the Department of Agriculture’s spray program. That represented 23 percent of the amount paid by the towns for the service.

An aerial tree mortality survey conducted last year by the department and the state Department of Environmental Protection found a total of 30,902 trees killed by repeated defoliations by gypsy moths since 2006.

Two to three consecutive years of significant defoliation – defined as 75 percent or more – can kill an otherwise healthy tree. Any gypsy moth defoliation can make trees more susceptible to other damage that can lead to the death of the tree. Oak trees are the preferred host for gypsy moths, but the caterpillars can be found feeding on almost any tree.

“The main goal of the department’s gypsy moth suppression program is to prevent the loss of trees and protect our forests, which are important wildlife habitats as well as filters for the air we breathe,” Fisher said. “We will continue to work cooperatively with the state DEP, the U.S. Forest Service and New Jersey’s congressional delegation to ensure this program is available to assist towns experiencing problems with gypsy moth caterpillars.”

Starting next month and continuing through January, the department will conduct egg mass surveys in towns that request it to determine what areas qualify for next year’s spray program. If the residential or recreational forest has an average of more than 500 egg masses per acre, and is at least 50 acres in size it may qualify for participation in the program.

Each year, since 1970, gypsy moth caterpillars have caused varying degrees of defoliation – between 1,910 and 800,000 acres of forested land.

To access the detailed 2009 New Jersey Gypsy Moth Aerial Defoliation survey and for more information on the gypsy moth suppression program, click here. For national gypsy moth information, click here.