Department of Agriculture | NJ GYPSY MOTH POPULATIONS RISE skip to main content skip to main navigation
Photo of a gypsy moth caterpillar - Click to enlarge
NJDA Aerial Survey Shows Increased Tree Damage Over Last Year


For Immediate Release: July 26, 2013
Contact: Lynne Richmond
(609) 633-2954

(TRENTON) – This summer’s annual New Jersey Department of Agriculture statewide gypsy moth aerial defoliation survey showed 2,887 acres of trees in 51 municipalities in 17 counties received moderate to severe damage this year from the leaf-eating invasive pests.

In 2012, 1,068 acres of trees in 21 municipalities in 10 counties were defoliated by gypsy moth caterpillars -- the lowest recorded defoliation since the Department’s Gypsy Moth Suppression Program began in 1970.

“While we have seen very low gypsy moth populations over the last few years, we must continue intense surveillance, as well as treatment to suppress this damaging insect,” said New Jersey Secretary of Agriculture Douglas H. Fisher.  “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.”

The defoliation survey was conducted in late June and early July.  Tree damage was found in Atlantic, Bergen, Burlington, Camden, Cumberland, Essex, Gloucester, Hunterdon, Mercer, Middlesex, Monmouth, Morris, Ocean, Passaic, Somerset, Sussex and Warren counties.  The most damage seen was in Bloomingdale Borough and West Milford Township, both in Passaic County, which had a total of 1,087 acres of trees heavily damaged.   For more details from the survey, go to www.nj.gov/agriculture/divisions/pi/pdf/2013gmsurvey.pdf.

The Department of Agriculture will conduct an egg mass survey this fall to determine where spraying is 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 of the bugs.

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. 

Gypsy moth populations can be cyclical.  Tree damage from the insects 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.

Vigilance is necessary for continued success of the program.  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 more information on New Jersey’s gypsy moth suppression program, visit: www.nj.gov/agriculture/divisions/pi/prog/gypsymoth.html.   Also, for national gypsy moth material, visit www.na.fs.fed.us/fhp/gm/.