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NJDA Aerial Survey Shows Almost 300,000 Acres of Trees Defoliated

For Immediate Release: July 22, 2015
Contact: Lynne Richmond
(609) 633-2954 

(TRENTON) – The New Jersey Department of Agriculture’s annual aerial survey of New Jersey conducted between June 17 and June 29 showed a major increase in tree damage from gypsy moth caterpillars this year.  An estimated 290,696 acres of trees in 175 municipalities in 20 counties were defoliated as compared to 1,330 acres in 24 towns in 11 counties in 2014.

Most of the tree damage was in the seven northernmost counties in the state, with the highest concentrations in Sussex, with 112,149 acres; Passaic with 61,386 acres; and Morris with 60,699.  The hardest hit towns were West Milford in Passaic County with 40,632 acres of trees defoliated and Jefferson Township in Morris County with 22,562 acres. 

“The Department of Agriculture’s intense surveillance program is designed to keep gypsy moth populations at bay,” said New Jersey Secretary of Agriculture Douglas H. Fisher.  “When populations increase dramatically like this year, we will aggressively survey to determine the severity of next year’s gypsy moth problem and recommend spraying in areas where it is warranted.”

All counties except for Hudson experienced some amount of tree damage from gypsy moths this year.  For more details from the survey, go to  Advisory letters will be sent to the impacted municipalities along with applications for ground egg mass surveys this fall.  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. 

This year, the Department conducted a spray program on 288 acres in Morris County, including two residential areas and 114 acres in Mahlon Dickerson Reservation in Jefferson Township, and 40 acres in Silas Condict Park in Kinnelon Borough.  Those areas received a single application of the insecticide Bacillus thuringiensis, or Bt. Bt is a non-chemical, “minimal risk” insecticide that only kills caterpillars. It does not harm other insects, animals or humans. It lasts only five to seven days before being broken down by natural forces. To view the Department’s 2015 spray program interactive map, go to

Gypsy moth populations can be cyclical.  Tree damage from the insects reached a recent 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 collapsed over the last several years.  There was a record low in 2012, when only 1,068 acres of trees sustained damage from the leaf-eating pests.

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:   Also, for national gypsy moth material, visit