New York State faces mounting pressure from invasive insects that arrived without natural predators to control their populations. These non-native species have cost the state billions of dollars in damage to forests, agricultural crops, and urban landscapes since their introduction.
From the emerald ash borer devastating ash tree populations across the state to the spotted lanternfly threatening the $350 million grape and apple industries, you need to recognize these destructive insects before they cause irreversible harm.
Understanding how to identify, report, and respond to these ten species helps protect New York’s forests, farms, and communities while supporting statewide monitoring efforts coordinated by the Department of Environmental Conservation and regional partnerships.
1. Emerald Ash Borer
The emerald ash borer (Agrilus planipennis) stands as one of New York’s most economically damaging invasive insects since its discovery in the state. This metallic green beetle measures approximately half an inch long and feeds exclusively on ash trees, making every native ash species vulnerable to attack.
Adult beetles emerge in late spring and feed on ash foliage, causing minimal visible damage. The real destruction comes from their larvae, which tunnel beneath the bark and create serpentine galleries that disrupt the tree’s ability to transport water and nutrients. Infested trees display characteristic signs including crown dieback starting at the top, increased woodpecker activity as birds hunt for larvae, D-shaped exit holes about one-eighth inch in diameter, and vertical bark splits revealing larval galleries underneath.
Since the emerald ash borer arrived in New York, millions of ash trees have died, costing billions in removal, replacement, and lost timber value. The beetle spreads naturally through adult flight but travels much farther distances when people move infested firewood, nursery stock, or wood products. New York maintains quarantines restricting the movement of ash materials from infested counties to slow the spread.
Important Note: Trees typically die within two to four years after initial infestation. Early detection provides the best chance for treatment success, as systemic insecticides can protect high-value specimen trees when applied before significant larval feeding occurs.
Management approaches include monitoring for adult beetles and signs of infestation, removing severely infested trees to reduce beetle populations, and treating valuable ash trees with systemic insecticides applied by certified professionals. The state encourages residents to preserve healthy ash trees through proactive treatment rather than waiting for infestation signs to appear.
2. Spotted Lanternfly
The spotted lanternfly (Lycorma delicatula) represents one of New York’s newest and most concerning invasive threats to agriculture and outdoor recreation. This planthopper from Asia first appeared in New York City in 2020 and has since spread to multiple counties across the state, with populations fluctuating dramatically from year to year.
Adult spotted lanternflies are about one inch long and half an inch wide, displaying visually striking wings. When wings are folded, they appear gray with black spots and a distinctive brick-like pattern near the tips. When wings spread during jumping or flying, brilliant red hindwings with black spots become visible, along with a yellow abdomen banded in black. Nymphs look completely different—early instars are black with white spots, while later instars develop red coloring before reaching adulthood.
These insects feed on sap from over 70 plant species by piercing bark and sucking fluids, weakening plants and making them vulnerable to disease and other pests. Their preferred host is tree of heaven, an invasive tree species, but they also attack black walnut, maples, grapes, hops, apples, and stone fruits. The feeding process produces massive amounts of sticky honeydew that promotes sooty mold growth, interferes with photosynthesis, attracts swarms of other insects, and creates unpleasant conditions for outdoor activities.
Key Insight: Spotted lanternflies spread primarily through human activity rather than natural dispersal. They lay egg masses on vehicles, outdoor furniture, firewood, stone, and equipment, hitchhiking to new locations when these items are transported.
New York’s grape and apple industries, valued at over $350 million annually, face significant threats from spotted lanternfly populations. The state has implemented quarantines restricting the movement of goods from infested areas and conducts extensive trapping surveys in high-risk zones. Residents can help by inspecting outdoor items before traveling, scraping egg masses into soapy water or hand sanitizer, and reporting sightings through iMapInvasives.
NYC Parks shifted its guidance from aggressive eradication efforts to accepting that spotted lanternflies are established and focusing on slowing their spread. While individual pest control has limited impact on overall populations, collective community action helps delay expansion into new agricultural regions.
3. Asian Longhorned Beetle
The Asian longhorned beetle (Anoplophora glabripennis) poses such a severe threat to New York’s hardwood forests and urban trees that it remains under federal quarantine wherever detected. This large, distinctive beetle measures one to one-and-a-half inches long with a shiny black body covered in white spots and dramatically long antennae banded in black and white.
Native to China and Korea, this wood-boring insect attacks healthy hardwood trees including maples, birches, elms, willows, poplars, and horsechestnuts—species that dominate New York’s forests and urban landscapes. Female beetles chew distinctive oval pits in bark to deposit eggs, and larvae tunnel deep into wood, creating extensive galleries that structurally weaken trees and eventually kill them within three to five years.
Visible signs include perfectly round exit holes about three-eighths inch in diameter, sawdust-like frass at the tree base or in branch crotches, oozing sap from egg-laying sites, and dead branches in the upper crown. The beetles spread primarily through human transport of infested wood products, firewood, and packing materials rather than through natural dispersal.
| Detection Method | Best Timing | What to Look For | Action Required |
|---|---|---|---|
| Visual tree inspection | July-October when adults active | Round exit holes, sawdust piles, egg pits | Report immediately to DEC |
| Firewood examination | Year-round | Larvae, pupae, or adults in wood | Do not transport; report finding |
| Branch dieback monitoring | Spring-Summer | Dead branches, unusual patterns | Professional arborist inspection |
| Community surveys | Peak adult season | Multiple infested trees in area | Contact state forestry officials |
New York has faced multiple Asian longhorned beetle infestations, most notably in New York City and Long Island. Federal and state agencies respond aggressively with quarantines, intensive monitoring, and removal of all host trees within a half-mile radius of infested trees. This drastic approach aims for complete eradication before the beetle can establish permanent populations.
Pro Tip: Never transport firewood long distances. Buy local firewood or use certified heat-treated wood. Asian longhorned beetles can survive in firewood and establish new infestations hundreds of miles from their origin point.
4. Brown Marmorated Stink Bug
The brown marmorated stink bug (Halyomorpha halys) has become a familiar agricultural pest and household nuisance across New York since its introduction from Asia. This shield-shaped insect measures about three-quarters of an inch long, displaying mottled brown coloring with distinctive alternating light and dark bands on its antennae and a white or pale pattern along the edges of its abdomen.
These versatile feeders attack an enormous range of crops including apples, peaches, soybeans, sweet corn, tomatoes, peppers, and various ornamental plants. Their piercing-sucking mouthparts extract plant fluids while injecting enzymes that cause dimpling, scarring, and internal tissue damage, making produce unmarketable. Agricultural losses in heavily infested regions have reached millions of dollars during peak population years.
Beyond crop damage, brown marmorated stink bugs seek indoor shelter during fall months, congregating in attics, wall voids, and other protected spaces to overwinter. They don’t reproduce indoors, cause structural damage, or bite people, but they release their characteristic foul odor when disturbed or crushed. Large aggregations inside homes can number in the hundreds or thousands, creating significant nuisance issues.
Control strategies emphasize prevention over eradication. For homes, seal entry points around windows, doors, vents, and utility penetrations before fall using caulk and weather stripping. Screen attic vents and repair damaged window screens. For gardens and orchards, row covers protect crops during peak feeding periods, though repeated insecticide applications provide only moderate control due to the bugs’ hard exoskeleton and mobility.
Common Mistake: Many insecticides labeled for other stink bug species prove ineffective against brown marmorated stink bugs. Research products specifically tested on this species, or accept that complete elimination is unrealistic while focusing on exclusion methods.
Natural predators are beginning to exploit brown marmorated stink bugs as a food source. The samurai wasp, a parasitoid native to Asia, has been detected parasitizing stink bug eggs in some areas, potentially providing biological control over time as ecosystems adapt to this established invader.
5. Hemlock Woolly Adelgid
The hemlock woolly adelgid (Adelges tsugae) appears as tiny, aphid-like insects covered in distinctive white, woolly wax that protects their colonies at the base of hemlock needles. Native to Asia, this pest has caused widespread mortality of eastern and Carolina hemlocks across their range, with significant ecological consequences extending far beyond individual trees.
These insects measure only 1.5 millimeters long and are often difficult to see individually, but their white woolly masses become conspicuous on the underside of hemlock branches, particularly visible from late fall through early spring. Adelgids feed by inserting their needle-like mouthparts into twig tissue and sucking sap, which prevents new growth and causes needles to turn grayish-green before dropping prematurely.
Infested hemlocks typically die within a few years as they lose the ability to photosynthesize and transport nutrients effectively. The ecological impacts parallel those of Dutch elm disease and chestnut blight—hemlocks provide critical stream temperature regulation through shading, prevent erosion along stream banks, create essential habitat for numerous wildlife species, and contribute to forest diversity and structure.
The adelgid spreads through multiple pathways including storm winds, migratory birds hitchhiking the insects between locations, mammals brushing against infested branches, human clothing and equipment, and infested nursery stock planted in new areas. New York’s hemlock forests have suffered extensive mortality, particularly in eastern counties where adelgid populations have been established longest.
Management strategies combine biological control through releasing predatory beetles that feed exclusively on hemlock woolly adelgid, applying horticultural oils to smother adelgid colonies on accessible branches, and treating high-value specimen trees with systemic insecticides. The state monitors adelgid spread through survey programs and regulates nursery stock movement to prevent introduction into uninfested areas.
6. Spongy Moth
The spongy moth (Lymantria dispar), formerly known as gypsy moth, ranks among the most destructive invasive forest pests in North America, having defoliated over 92 million acres since its accidental introduction in Massachusetts during the 1860s. New York experiences periodic outbreaks following predictable 10-15 year population cycles.
Caterpillars are easily identified by five pairs of blue dots followed by six pairs of red dots running along their backs. They emerge from egg masses in spring, typically late April or early May, and feed voraciously on foliage for six to eight weeks. While they show strong preferences for oak leaves, spongy moth caterpillars consume over 300 different tree and shrub species when populations explode. A single caterpillar can eat up to one square foot of foliage during its development.
During outbreak years, forests can be completely stripped of leaves by early summer, creating a distinctive winter-like appearance in mid-June. The stress from repeated defoliation weakens trees, making them vulnerable to secondary pests, diseases, and environmental stressors like drought. Multiple consecutive years of defoliation often result in tree mortality, particularly for oaks and other preferred species.
Key Insight: Female spongy moths cannot fly, which naturally limits spread. However, egg masses hitchhike on vehicles, firewood, outdoor equipment, and recreational gear, allowing the pest to jump hundreds of miles and establish new populations far from existing infestations.
Each tan, fuzzy egg mass contains 500 to 1,000 eggs and can appear on tree bark, buildings, outdoor furniture, vehicles, trailers, and almost any outdoor surface. They become darker and softer over time as they age. Management approaches include manually destroying egg masses during winter months by scraping them into soapy water, applying bacterial insecticides containing Bacillus thuringiensis during early larval stages when caterpillars are small, setting pheromone traps to monitor population levels, and using barriers like burlap bands to trap caterpillars as they move up and down tree trunks.
7. Japanese Beetle
The Japanese beetle (Popillia japonica) inflicts damage through both adult and larval life stages, making it a particularly challenging pest for New York homeowners, farmers, and landscapers. Adult beetles display metallic green bodies with copper-colored wing covers and distinctive small white tufts of hair along their sides, measuring about half an inch long.
These beetles feed on over 300 plant species, with particular fondness for roses, grapes, linden trees, fruit trees, and various ornamental plants. Adults skeletonize leaves by consuming tissue between the veins, leaving behind delicate lace-like patterns that severely reduce photosynthetic capacity. They often feed in groups, with their feeding damage releasing volatile compounds that attract additional beetles in a destructive cycle.
The white, C-shaped grubs live in soil and feed on grass roots from late summer through the following spring. Heavy grub infestations create brown patches in lawns where grass dies from root damage, and turf can be rolled back like carpet. The grubs overwinter in soil below the frost line, resume feeding in spring, and pupate in early summer to emerge as adults in late June.
Adult beetles follow predictable daily patterns, becoming most active during warm, sunny days. They’re sluggish in early morning when temperatures are cooler, making this the ideal time for hand-picking on small plantings. Peak adult populations occur from late June through August, with populations gradually declining as fall approaches.
- Adult control methods: Hand-picking into soapy water in early morning, neem oil sprays requiring repeated applications, pyrethrin-based insecticides for severe infestations, Japanese beetle traps placed away from valued plants
- Grub control strategies: Beneficial nematodes applied to soil in late summer targeting young grubs, milky spore disease providing long-term biological control, preventive grub control insecticides applied in mid to late summer
- Cultural practices: Maintaining healthy, vigorous turf through proper watering and fertilization, avoiding planting highly attractive species in vulnerable areas
8. European Corn Borer
The European corn borer (Ostrinia nubilalis) represents one of the most economically important agricultural pests affecting New York’s corn production, sweet corn crops, and various other plants. This invasive moth from Europe arrived in North America over a century ago and has since become established throughout the corn-growing regions.
Adult moths display tan or light brown coloring with irregular darker bands across their wings, measuring about one inch in wingspan. Females are slightly larger and paler than males. The larvae, or caterpillars, appear cream-colored or pinkish with brown heads and distinctive dark spots along each body segment, growing up to one inch long at maturity.
European corn borer caterpillars tunnel into corn stalks, ears, and tassels, creating entry holes and leaving behind frass. This boring behavior causes multiple problems including broken stalks that fall before harvest, reduced ear development and kernel quality, entry points for stalk rot diseases, and direct feeding damage to developing ears. The pest completes one to three generations per year in New York depending on location, with southern regions experiencing more generations than northern areas.
Beyond corn, European corn borers attack over 300 plant species including peppers, potatoes, beans, asters, dahlias, and chrysanthemums. The caterpillars bore into stems, weakening plants and disrupting nutrient transport. In vegetable crops, they may tunnel directly into fruits, causing unmarketable damage.
Pro Tip: Proper timing of control measures depends on understanding the pest’s life cycle. Monitor for egg masses on corn leaves and target young larvae before they bore into stalks, when they’re most vulnerable to insecticides and biological control agents.
Integrated management combines cultural practices like destroying crop residues after harvest to eliminate overwintering sites, crop rotation to disrupt pest cycles, planting Bt corn varieties that produce proteins toxic to corn borers, timely insecticide applications when monitoring indicates economic thresholds are reached, and conserving natural enemies including parasitic wasps and predatory insects.
9. Viburnum Leaf Beetle
The viburnum leaf beetle (Pyrrhalta viburni) has emerged as a serious threat to native and ornamental viburnum plants throughout New York. This European beetle was first discovered in North America in Ontario, Canada in 1947 and crossed into New York in 1996, subsequently spreading across much of the northeastern United States.
Adult beetles measure about one-quarter inch long with brown coloring, while larvae appear yellow-green with dark spots and grow to about one-third inch long. Both life stages feed on viburnum foliage, but larvae cause the most severe damage. They emerge in spring and feed between leaf veins in a characteristic pattern, consuming all leaf tissue except the major veins and midrib, creating a skeleton-like appearance.
Adults emerge in summer and continue feeding on foliage before females lay eggs. They chew small holes in young viburnum twigs and deposit eggs in neat rows, then cap each hole with a combination of chewed wood and feces that appears as distinctive raised bumps along the twigs. These egg-laying sites remain visible throughout winter, providing the best time for detection and manual control.
Repeated defoliation over several years progressively weakens viburnums, reducing their vigor and eventually killing plants. Some viburnum species show higher susceptibility than others—arrowwood and European cranberrybush viburnums suffer most severely, while doublefile and Judd viburnums demonstrate resistance through chemical or physical defenses.
Management strategies emphasize prevention and early intervention. Inspect viburnums for egg-laying scars on twigs during winter and prune out infested branches before eggs hatch in spring. When larvae appear, apply insecticidal soap or neem oil sprays to control populations while they’re small. For severe infestations on susceptible species, consider replacing plants with resistant viburnum varieties or alternative shrub species.
10. Lily Leaf Beetle
The lily leaf beetle (Lilioceris lilii) devastates true lilies and fritillaries in New York gardens with its voracious feeding on both foliage and flowers. This striking European beetle first appeared in North America in Montreal around 1945 and reached New York by the 1990s, steadily expanding its range since then.
Adult beetles are unmistakable—brilliant scarlet red bodies measuring about one-third inch long with black heads, legs, and undersides. When disturbed, they often drop from plants and land on their backs, displaying their black underside as camouflage. The larvae appear even more unusual, looking like small slugs covered with their own wet, dark excrement as protection from predators and environmental stress.
These beetles attack true lilies, Asiatic hybrids, Oriental hybrids, and fritillaries with devastating efficiency. Both adults and larvae consume leaves, buds, and flowers, often completely defoliating plants if left unchecked. Adults emerge in early spring, mate, and lay bright orange eggs in clusters on the underside of lily leaves. Larvae hatch and begin feeding immediately, growing through four instars while remaining covered in fecal material.
The beetles complete their life cycle through pupation in soil, with new adults emerging to feed and potentially produce a second generation in warmer areas. Their arrival has significantly impacted gardeners’ ability to grow lilies, forcing many to abandon these popular ornamentals or implement intensive management programs.
Important Note: Hand-picking remains surprisingly effective for lily leaf beetle control in home gardens. Check plants daily during growing season, looking for adults on foliage and orange eggs on leaf undersides. Drop beetles into soapy water—they’ll try to escape by dropping and hiding.
Control methods combine vigilant monitoring with multiple approaches including daily hand-picking of adults, eggs, and larvae during growing season, neem oil or spinosad sprays applied when damage is first noticed, soil drenches with systemic insecticides for severe infestations, and mulching around lilies to discourage pupation in surrounding soil.
Conclusion
The ongoing challenge of invasive insects requires sustained vigilance from New York residents, farmers, foresters, and conservation professionals. Each of these ten species demonstrates how quickly non-native pests can establish, spread, and cause extensive damage when introduced to new environments lacking natural population controls.
Your participation in monitoring and reporting programs directly supports state management efforts. Many invasive insect infestations are first detected by observant residents who notice unusual insects or unexplained plant damage. New York maintains iMapInvasives, a centralized reporting system where you can submit photos and location information for suspected invasive species. Regional Partnerships for Regional Invasive Species Management (PRISMs) coordinate local responses and provide resources for identification and control.
Prevention remains the most cost-effective approach to invasive species management. Simple actions significantly reduce accidental spread including not transporting firewood between counties or states, buying local firewood or certified heat-treated wood, inspecting plants carefully before purchasing from nurseries, cleaning equipment when moving between properties, and checking vehicles, outdoor furniture, and gear for hitchhiking insects or egg masses before traveling.
Early detection dramatically improves management outcomes and reduces costs. Familiarize yourself with the distinctive features of these ten species, regularly inspect trees and plants on your property for signs of damage, monitor pest populations in gardens and landscapes throughout the growing season, and report sightings promptly to appropriate authorities through iMapInvasives or direct contact with the Department of Environmental Conservation.
New York’s diverse ecosystems—from the Adirondack forests to Hudson Valley agricultural lands to New York City’s urban parks—face persistent threats from invasive species. The state’s forests, agricultural economy, and natural heritage depend on community engagement in detection, reporting, and prevention efforts. By staying informed about these ten harmful invasive insects and taking action when you encounter them, you contribute to protecting New York’s environmental and economic health for generations to come.
