Gypsy moths on decline in New Jersey

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Gypsy moth larvae consume the leaves of more than 500 species of trees, shrubs and plants.  Wikipedia photo by Didier Descouens Gypsy moth larvae consume the leaves of more than 500 species of trees, shrubs and plants. Wikipedia photo by Didier Descouens Aerial survey shows less than half the tree damage observed last year

TRENTON – Tree damage caused by gypsy moth caterpillars this year is less than half of what it was last year, and the losses were mostly concentrated in the northern counties, according to New Jersey Secretary of Agriculture Douglas H. Fisher.

The New Jersey Department of Agriculture’s annual statewide gypsy moth aerial defoliation survey showed 1,330 acres of trees in 24 municipalities in 11 counties were defoliated in 2014, compared with 2013, when 2,887 acres of trees in 51 towns in 17 counties were harmed.

“For the last five years, New Jersey has experienced very substantially less gypsy moth damage through a combination of favorable weather conditions, an army of beneficial insects, and intense surveillance,” Fisher said in a news release issued July 17.

The defoliation survey was conducted in late June and early July. The tree damage observed was centered in Morris, Passaic, Bergen and Sussex counties, which sustained 1,110 acres of tree damage. Minimal amounts of damage were seen in Burlington, Camden, Hunterdon, Mercer, Middlesex, Ocean and Warren counties. For details from the survey see

The gypsy moth is the most destructive forest insect to infest state forests, according to the NJDA. Tree damage occurs during the larval stage, when the caterpillars feed on the leaves of trees, shrubs and other plants.

Gypsy moth populations can be cyclical. Tree damage reached a high of 339,240 in 2008, but through the combination of the department’s aggressive spray program, a number of beneficial insects, and weather that supported a fungus that impacts gypsy moths, populations have collapsed over the last several years, the state said. There was a record low in 2012, when only 1,068 acres of trees sustained damage from the leaf-eating pests. 

The Department of Agriculture will conduct an egg mass survey this fall to determine where spraying might be warranted.

Gypsy moth caterpillars lay their eggs on trees and emerge in May and early June. This year, no spray program was needed due to low populations.

To qualify for the spray program, a residential or recreational forest must have an average of more than 500 egg masses per acre and be at least 50 acres in size. A single egg mass contains up to 1,000 eggs. 

Vigilance is necessary for continued success of the program, state officials said. Two to three consecutive years of significant defoliation (defined as 75 percent or more) can kill an otherwise healthy tree. However, 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 in the vicinity.

For information on New Jersey’s gypsy moth suppression program see  For national gypsy moth information see

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