New Jersey is home to several invasive insect species that threaten trees, crops, and landscaping across the state. The spotted lanternfly is the most visible problem right now, with every county in New Jersey under quarantine, but it’s far from the only pest residents should know about. Here’s what’s actively affecting the state and what you can do about it.
Spotted Lanternfly
The spotted lanternfly is the invasive bug most New Jersey residents encounter firsthand. Originally from Asia, it feeds on more than 70 plant species by piercing stems and sucking sap, weakening trees and leaving behind a sticky residue called honeydew that promotes black mold growth. Grapevines, fruit trees, hardwoods, and ornamental plants are all targets.
Every county in New Jersey is now under a state quarantine. That means you’re expected to inspect vehicles, trailers, and any outdoor items before moving them around or out of the state. Egg masses, which look like smears of dried mud on flat surfaces, are the primary way the insect hitchhikes to new areas.
The life cycle matters for control. Egg masses overwinter from fall through early spring on trees, rocks, outdoor furniture, and vehicles. Nymphs emerge in spring and go through several stages before becoming the distinctive gray-and-red winged adults in late summer. Adults tend to fly to new trees to feed as the season progresses, which is when populations become most noticeable.
What You Can Do
The New Jersey Department of Agriculture recommends a few straightforward actions. Crush nymphs and adults when you see them. Scrape egg masses off surfaces into a plastic bag with rubbing alcohol or hand sanitizer, then throw them in the trash. Simply scraping them onto the ground isn’t enough, as the eggs can still hatch.
If Tree of Heaven grows on your property, consider removing it. This invasive tree is the spotted lanternfly’s preferred host, and eliminating it along with wild grape and oriental bittersweet can reduce local populations. Herbicide is recommended when removing Tree of Heaven to prevent regrowth from the roots.
For egg masses you can’t easily scrape, horticultural oils applied at a concentration of at least 3 percent kill up to 75 percent of treated eggs. Products containing paraffinic or mineral oils are the most effective options tested. Soybean oil also works but requires a much higher concentration (around 50 percent) to achieve similar results. For nymphs and adults, many contact insecticides are effective, though starting with the least toxic option is the recommended approach.
Emerald Ash Borer
The emerald ash borer is a metallic green beetle, roughly half an inch long, that kills ash trees by tunneling under the bark as larvae. The tunneling cuts off the tree’s ability to transport water and nutrients, and most untreated trees die within three to five years of infestation. Across the U.S. and Canada, this beetle has killed tens of millions of ash trees since 2002.
New Jersey has approximately 24.7 million ash trees, concentrated mostly in the northwestern part of the state. About 24 percent of the state’s forests contain ash, and roughly 9 percent of total forested area is susceptible to infestation. The beetle was first discovered in New Jersey in May 2014 in Somerset County and has since spread to Bergen, Burlington, Essex, Hunterdon, Mercer, Middlesex, and Monmouth counties.
Signs of infestation include thinning canopy, D-shaped exit holes about an eighth of an inch wide in the bark, S-shaped tunnels under the bark, and increased woodpecker activity (they feed on the larvae). If you have ash trees you want to protect, treatment options include soil-applied treatments, trunk injections, and bark sprays. These need to be applied preventively or at the earliest signs of infestation, as heavily damaged trees generally can’t be saved. A certified arborist can assess whether treatment is worthwhile for your trees.
Spongy Moth
Formerly known as the gypsy moth, the spongy moth is a defoliator, meaning its caterpillars eat leaves rather than boring into wood. Oak trees are the primary target, but the caterpillars feed on hundreds of tree species. A single year of heavy defoliation weakens trees significantly, and two or three consecutive years can kill them.
Spongy moth populations cycle between low and high levels over roughly 10-year intervals. During low years, natural controls like parasites, predators, and a fungal disease keep populations in check. During peak years, these natural controls can’t keep up, and large areas of forest canopy get stripped bare. When that happens, the New Jersey Department of Agriculture conducts aerial spray treatments over residential and recreational areas using a biological insecticide (a naturally occurring bacterium that targets caterpillars but is harmless to people, pets, and most other insects).
The scale of these treatments varies dramatically by year. In 2021, for example, only 50 acres in Cape May County were treated. During outbreak years, the numbers are far higher. The state surveys egg mass density each year to determine which areas qualify for suppression programs.
Box Tree Moth
The box tree moth is the newest invasive insect threat in New Jersey, confirmed in Cape May County in 2026. Native to temperate and subtropical Asia, this moth targets boxwood plants, which are among the most common ornamental shrubs in residential landscaping across the Northeast. The caterpillars can completely strip a boxwood of its leaves, and heavy infestations kill the plant.
The moth’s spread has been rapid elsewhere. It was first detected in Europe in 2007 and expanded across the continent within a decade. It reached Canada in 2018 and the United States in 2021 in upstate New York. When boxwood is depleted, the caterpillars move to secondary hosts including burning bush and Japanese spindletree. The New Jersey Department of Agriculture has established a quarantine in response to the Cape May detection, and early reporting is critical to limiting its spread.
Asian Longhorned Beetle: A Success Story
Not every invasive insect story in New Jersey is ongoing. The Asian longhorned beetle, a large black-and-white spotted insect that attacks maples, elms, birches, and other hardwoods, was officially declared eradicated from the state after more than a decade of effort. Eradication required removing every infested tree and conducting surveys until no signs of beetle activity remained.
The success came with a warning, though. The beetle still exists in other parts of the country, and it can spread through infested firewood. State officials continue to urge residents not to move firewood and to inspect trees regularly for signs of infestation: round exit holes about the size of a pencil eraser, sawdust-like material at the base of trees, and unusual branch dieback.
How to Report a Sighting
If you spot an insect you believe is a regulated invasive pest, New Jersey has a dedicated hotline: 1-833-BAD-BUG0 (1-833-223-2840). You can also contact the NJDA Division of Plant Industry directly at 609-406-6939 or by email at plantindustry@ag.nj.gov. When reporting, note the location, take photos if possible, and identify the host plant the insect was on.
Early detection makes a measurable difference in containment. The Asian longhorned beetle eradication succeeded in part because infestations were caught and isolated quickly. The same principle applies to newer threats like the box tree moth, where a single report from a resident can trigger the response that keeps a localized problem from becoming a statewide one.