⚫ New Jersey says more than 13,000 acres need treatment for a tree-killing insect

⚫ Just 1,400 acres were recommended for treatment a year ago

⚫ Treatment would take place in May and June


New Jersey officials believe that tens of thousands of acres need to be treated for the pest formerly known as the gypsy moth.

The latest estimates suggest that the tree-killing insect is expanding its reach again in the Garden State.

The 2025 recommendation from the New Jersey Department of Agriculture calls for 13,712 acres of residential- and county-owned properties to be sprayed for Lymantria dispar dispar, or LDD.

NOTE: For decades, these pests have been known as gypsy moths. The Entomological Society of America changed its name in March 2022, as the previous label contained an ethnic slur.

Where does NJ need treatment?

More than half of the recommended acreage is located in the northwest corner of New Jersey, in Sussex County. The recommendation also covers areas in Burlington, Cape May, Passaic, and Morris counties.

Just 1,400 acres were recommended in 2024 to take on the defoliators.

Lymantria dispar dispar (NJ Dept. of Agriculture)
Lymantria dispar dispar (NJ Dept. of Agriculture)
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“With the moth’s increase in activity, these treatments are critical in helping prevent the spread of this insect and reducing its population in future years,” said New Jersey Secretary of Agriculture Ed Wengryn.

According to the Department, the increased recommendation area is due to a couple reasons, including the lack of treatment in nearby states, as the pests travel by wind. Also, a dry summer resulted in a less active year for an LDD-killing fungus.

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The recommendation is based off of egg mass surveys that were conducted from August to December of last year.

LDD prefer oak trees, but the caterpillars can be found feeding on almost any tree. Just a season or two of LDD damage could kill a tree.

It's up to effected municipalities whether they want to participate in the spray treatment program. They have to foot the bill — ideally, the federal government would reimburse them for up to 50% of the cost, which can be substantial.

"You have these population spikes, but something has to break the cycle," said Joe Zoltowski, with the Department's Division of Plat Industry.

Treatment would take place in May and June. Officials use a biological insecticide that kills the LDD caterpillar when ingested.

LDD doesn't follow much of a pattern in New Jersey. In 2023, there were 5,100 acres recommended for treatment. The recommendation involved 9,000 acres in 2022. In 2019 and 2020, there were no areas of the state recommended for treatment.

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