Lymantria dispar dispar: The Tree-Killing Pest Expanding Its Reach in New Jersey

New Jersey is now facing a growing threat from invasive species- not only spotted lanternflies, but also Lymantria dispar dispar (LDD) moths, an invasive moth species causing widespread tree defoliation. As their populations expand across the state, homeowners and communities must take action. This article explores why LDD moths are spreading, their impact, and effective pest control solutions to protect local forests.

Lymantria dispar dispar: What Is It?

The Lymantria dispar dispar moth, formerly known as the gypsy moth, is a species of invasive moth. Males are smaller, with a wingspan of about 1.5 inches, and have brown, intricately patterned wings with feathery antennae. Females are larger, with a wingspan of around 2.5 inches, and have creamy white wings with faint dark markings, though they are flightless. The larvae (caterpillars) are hairy, dark-colored, and feature pairs of blue and red spots along their backs.

The name "gypsy moth" was officially changed because the term "gypsy" is considered a derogatory slur toward the Romani people. In 2021, the Entomological Society of America renamed the species to Lymantria dispar dispar as part of an initiative to remove harmful or offensive language from scientific names.

Where Do LDD Moths Live? Habitat and Geographical Range

LDD moths are an invasive species found across much of the northeastern and midwestern United States, as well as parts of the southeastern and central regions. Originally from Europe and Asia, they were introduced to North America in the late 1800s and have since spread widely due to their adaptability and lack of natural predators.Their range in the U.S. extends from New England and the Great Lakes region down to parts of Virginia and West Virginia, with continued expansion westward. Quarantine measures exist to slow their spread, but their ability to hitch rides on vehicles and outdoor equipment makes containment challenging.

LDD moths thrive in deciduous and mixed forests, particularly those dominated by oak, as their caterpillars prefer oak leaves. They are commonly found in suburban areas, parks, and woodlands, where they can defoliate large sections of trees.

What Do LDD Moths Eat?

LDD moths, particularly in their larval (caterpillar) stage, are voracious feeders that primarily consume the leaves of deciduous trees. Their preferred food source is oak, especially species like white oak and red oak, making forests with high oak populations particularly vulnerable to defoliation. However, LDD caterpillars are highly adaptable and will feed on over 300 species of trees and shrubs, including maple, birch, poplar, aspen, willow, apple, and beech. While they prefer hardwoods, they may also consume coniferous trees like pine, spruce, and hemlock, particularly if their primary food sources are depleted. This can be especially damaging, as conifers do not regenerate their needles as easily as deciduous trees regrow leaves.

Adult moths do not eat; their sole purpose is reproduction. The larvae cause the most damage, sometimes stripping entire forests of foliage, weakening trees and making them susceptible to disease, pests, and environmental stress.

What Are the Hazards of an LDD Moth Infestation?

An Lymantria dispar dispar (LDD) moth infestation poses serious ecological and economic threats, primarily due to the feeding habits of the caterpillars. These larvae are highly destructive defoliators, capable of stripping entire forests of their leaves. Severe or repeated defoliation weakens trees, making them more susceptible to diseases, secondary insect infestations, and environmental stressors like drought. This can lead to long-term forest decline and even tree mortality, disrupting ecosystems and reducing biodiversity.

Beyond environmental damage, LDD infestations can have significant economic consequences. The loss of hardwood trees impacts the timber industry, while defoliated landscapes reduce property values and tourism revenue in affected areas. Additionally, municipalities and homeowners often face high costs for pest control, tree maintenance, and cleanup efforts. LDD caterpillars also pose a nuisance to humans. Their sheer numbers can make outdoor spaces unpleasant, and their tiny hairs can cause skin irritation or allergic reactions in sensitive individuals. The presence of caterpillars, frass (droppings), and silk strands can make yards, parks, and recreational areas unusable during peak infestation periods. Due to their rapid spread and high reproductive capacity, LDD moths remain a major invasive pest requiring ongoing monitoring and management.

Why Are These Pests Expanding?

The LDD moth is expanding its geographical reach in New Jersey due to a combination of environmental factors, human activity, and the species' natural adaptability. Warmer temperatures, likely influenced by climate change, have created more favorable conditions for LDD populations to thrive in areas where extreme cold previously helped limit their spread. Milder winters allow more egg masses to survive, leading to larger outbreaks.

Human activity also plays a significant role in their expansion. LDD egg masses can attach to vehicles, firewood, outdoor furniture, and other objects, unintentionally spreading them to new locations. As people travel, particularly between infested and uninfested areas, they help transport these invasive pests beyond their previous range. Additionally, New Jersey’s diverse forests provide ample food sources for LDD caterpillars. The state has abundant oak, maple, and other hardwood trees that serve as prime feeding grounds. Without significant natural predators or widespread control measures, LDD populations continue to grow and spread. Their adaptability to different tree species and urban environments further accelerates their range expansion, making it increasingly difficult to manage infestations and prevent further ecological and economic damage.

Which Areas of New Jersey Are Most Affected?

In New Jersey, the expansion of Lymantria dispar dispar (LDD) moth populations has significantly impacted several counties. Recent assessments by the New Jersey Department of Agriculture have identified five counties—Burlington, Cape May, Morris, Sussex, and Warren—as areas requiring treatment due to severe infestations. These regions have experienced extensive defoliation, with tens of thousands of acres affected by the feeding activities of LDD caterpillars. Historically, Burlington County has faced recurrent LDD moth challenges. In 2017 and 2018, approximately 3,900 acres of residential and county-owned properties in Burlington and other northern counties underwent treatment to curb the pest's spread. This intervention led to an 80% reduction in affected areas compared to 2016.

The susceptibility of these counties can be attributed to their extensive hardwood forests, particularly those rich in oak species, which are preferred by LDD caterpillars. Without effective management, these infestations can lead to significant ecological and economic consequences, including tree mortality and increased costs for pest control and forest restoration. To combat the spread, New Jersey employs biological insecticides, such as Bacillus thuringiensis (B.t.), targeting LDD larvae during their feeding stages. Continuous monitoring and timely interventions are crucial to protect the state's forested areas from further damage caused by this invasive species.

How You Can Help Combat LDD Moth Infestations

New Jersey residents can take several proactive steps to help combat the spread of Lymantria dispar dispar (LDD) moths and minimize their impact on local forests and communities.

• Check for and Remove Egg Masses – LDD moth egg masses can be found on tree trunks, outdoor furniture, vehicles, and buildings from late summer to early spring. Residents should scrape them off into soapy water to destroy them.

• Limit the Transport of Infested Items – Egg masses can hitch a ride on firewood, campers, and other outdoor equipment. Before traveling, especially from infested areas, check and clean these items to prevent accidental spread.

• Use Burlap Traps for Caterpillars – Wrapping burlap around tree trunks can trap caterpillars, making it easier to collect and dispose of them before they reach maturity.

• Encourage Natural Predators – Birds, small mammals, and certain insects help control LDD populations. Planting native vegetation and avoiding broad-spectrum pesticides can support these beneficial species.

• Report Severe Infestations – Residents should notify local agricultural or forestry agencies about significant outbreaks to help coordinate targeted treatments.

As the spread of LDD moths continues to affect New Jersey's landscapes, it's crucial for both homeowners and businesses to stay vigilant, but LDD moths are not the only pests plaguing the Garden State. Twin-Boro is here to help with all of your residential pest control and commercial pest control needs. For more information or assistance, don’t hesitate to contact us.