More than 70,000 acres of Massachusetts forests suffered defoliation in a single year from just one invasive insect species. The Asian longhorned beetle outbreak in Worcester cost over $150 million for the removal of 34,000 trees, fundamentally changing the city’s urban canopy for decades.
These aren’t isolated incidents—they represent an ongoing crisis where non-native insects continue reshaping Massachusetts’ forests, gardens, and landscapes in ways that threaten both environmental health and economic stability.
You have the power to slow this invasion. Early detection through community reporting has proven essential for successful management of these insects, with smartphone technology putting forest protection capabilities directly in your hands.
Understanding what these invasive insects look like, where they attack, and how to report them transforms every Massachusetts resident into a potential first responder against ecological damage.
1. Emerald Ash Borer
The emerald ash borer (Agrilus planipennis) was first discovered in Massachusetts in Dalton in 2012, marking the beginning of a serious threat to the state’s ash tree population. This small Asian beetle has already killed thousands of ash trees across North America since its initial U.S. detection in 2002, and it continues spreading through Massachusetts primarily via transported firewood and wood packaging materials.
Adult emerald ash borers display distinctive metallic emerald green coloring on their bodies, measuring about half an inch long with a narrow, elongated shape. The most telling evidence of infestation appears as D-shaped exit holes in ash tree bark, roughly one-eighth inch in diameter, where adult beetles emerge after developing inside the tree. These uniquely shaped holes—flatter on one side and rounder on the other—distinguish emerald ash borer from other wood-boring insects.
Pro Tip: Woodpeckers actively feed on emerald ash borer larvae beneath bark, so heavy woodpecker damage on an ash tree often signals an infestation before you notice other symptoms. Look for areas where woodpeckers have stripped away bark patches to reach the larvae underneath.
The larvae cause the actual tree damage by creating serpentine galleries as they feed on the phloem layer just beneath the bark. This feeding disrupts the tree’s ability to transport water and nutrients, leading to crown dieback that typically starts at the top of the tree. You’ll notice branches becoming sparse and leafless, with the damage progressing downward over one to four years until the tree dies.
Infested trees may also display vertical bark splits, increased sprout growth from the trunk base as the tree struggles to survive, and thinning canopy with branches dying back from the tips. The larvae themselves appear cream-colored and segmented, with distinctive bell-shaped body segments when extracted from beneath bark.
Never transport firewood between locations, as this represents the primary method of emerald ash borer spread across Massachusetts. The insect was found just 20 miles from the state’s western border before appearing in Dalton, demonstrating how quickly it can advance through firewood movement. Buy firewood where you’ll burn it, or gather it on-site when camping. Report suspected emerald ash borer activity to UMass Extension with clear photographs showing D-shaped exit holes or larvae.
2. Asian Longhorned Beetle
The Asian longhorned beetle (Anoplophora glabripennis), also known as the starry sky beetle, arrived in Massachusetts through wood packing materials from Asia and triggered a full-scale eradication program in Worcester in 2008. This large, distinctive beetle attacks several important native tree species including maple, birch, willow, and elm, with authorities removing more than 20,000 infested trees in Worcester County at costs exceeding $150 million.
You’ll immediately recognize adult Asian longhorned beetles by their size and striking appearance. These insects measure one to one and a half inches long with glossy black bodies covered in small white spots that create a starry appearance. Their long antennae—up to twice their body length—display distinctive black and white banding. The beetles emerge from trees in summer and remain active through fall.
The damage begins when female beetles chew oval depressions in bark to lay eggs. The eggs hatch within two weeks, and larvae bore into the tree to feed on the living tissue just under the bark that carries nutrients throughout the tree. This feeding creates extensive tunneling that weakens the tree structurally and eventually kills it.
Key Insight: The Asian longhorned beetle has been spotted in central Massachusetts and even near the Arnold Arboretum in Boston at Faulkner Hospital. Federal and state agencies continue working to find infestation boundaries, remove infested trees, and replant areas where trees were removed in the eradication effort.
Exit holes from Asian longhorned beetles appear perfectly round, measuring about three-eighths inch in diameter—noticeably larger than most native borer holes. You’ll often find coarse sawdust (frass) accumulating at the tree’s base or in bark crevices near exit holes. Trees may also show sap weeping from egg-laying sites and dieback starting in the upper crown.
Check maple trees carefully from July through October when adult beetles are active. Look at the trunk, branches, and even the underside of leaves where beetles sometimes rest. The beetles don’t fly well, so infestations tend to remain localized initially, making early detection crucial for containment.
Wood packing material from Asia—pallets, crates, and spools—continues bringing this pest into communities. Unsuspecting homeowners sometimes take this material home for various projects, unknowingly introducing beetles to new areas. If you see a large black beetle with white spots and long banded antennae, photograph it immediately and report it through the Asian Longhorned Beetle hotline at 508-852-8090.
3. Spongy Moth
The spongy moth (Lymantria dispar)—formerly called gypsy moth until the name change in 2021—ranks among the worst forest pest insects in North America. While populations have declined in Massachusetts in recent years, this invasive moth continues threatening forests by devouring leaves from more than 500 different tree and shrub species during periodic outbreak years.
Adult male spongy moths appear brownish-gray with darker wavy bands across their wings, measuring about one and a half inches across when wings are spread. They’re strong fliers that actively search for females during summer. Female moths are larger with white to cream-colored wings, but they cannot fly and remain near their egg masses after emerging.
The caterpillars cause extensive defoliation damage during late spring and early summer. You’ll recognize them by the distinctive paired dots along their backs—five pairs of blue dots followed by six pairs of red dots—with the entire body covered in long hairs that give them a fuzzy appearance. Large caterpillars can reach two inches long and consume enormous quantities of leaves daily.
During outbreak years, heavy infestations strip entire forests bare of leaves. The sound of caterpillar droppings (frass) falling from trees can become noticeably loud, and the accumulation of frass under trees creates significant nuisance problems. Trees weakened by complete defoliation become vulnerable to other pests and diseases, with multiple years of defoliation often proving fatal.
Important Note: Spongy moths are brought to new areas by people, with Massachusetts seeing new introductions regularly despite eradication efforts since European gypsy moths were first detected in 1974. Asian gypsy moth females can fly up to 12 miles, making them more dangerous than the European variety, and they feed on a broader range of host trees including conifers.
Egg masses appear as tan or buff-colored fuzzy patches about one to two inches long, typically laid on tree trunks, outdoor furniture, vehicles, firewood, or any protected surface. Each mass contains 500 to 1,000 eggs that overwinter and hatch in spring. The fuzzy covering protects eggs from weather and predators throughout winter months.
Scrape egg masses into containers of soapy water to destroy them before caterpillars emerge in spring. Use a putty knife or similar tool to remove the entire mass, ensuring you collect all eggs. Check outdoor items before moving them between locations, especially recreational vehicles, camping equipment, and firewood that spent time in outbreak areas.
Scientists have introduced biological controls including parasitic flies and fungi that help manage spongy moth populations naturally. These control methods have proven effective in reducing outbreak frequency and severity, though periodic population explosions still occur when conditions favor caterpillar survival.
4. Hemlock Woolly Adelgid
Hemlock woolly adelgid (Adelges tsugae) was first detected in Massachusetts in the Forest Park section of Springfield in the late 1980s. This small aphid-like insect feeds by sucking sap from eastern hemlock and Carolina hemlock trees, and it has now spread fairly widespread across the state, weakening many hemlocks to the point where overall tree health has seriously declined.
You’ll identify hemlock woolly adelgid infestations by the distinctive white woolly masses that appear at the base of hemlock needles, particularly on the underside of branches. These cotton-like egg sacs contain hundreds of tiny reddish-brown adelgids, with each generation producing the protective white wool that makes infestations easy to spot against the dark green needles. The wool appears most prominent from fall through early summer.
The adelgids insert their piercing-sucking mouthparts into young twig tissue to feed on stored starches in the xylem ray cells. This feeding depletes the tree’s nutrient reserves and disrupts the flow of water and nutrients. Infested trees show needle loss, branch dieback, and reduced growth rates. While hemlock woolly adelgid hasn’t killed trees outright in Massachusetts as dramatically as in southern states, it weakens hemlocks significantly and makes them vulnerable to other stressors.
Multiple generations per year allow hemlock woolly adelgid populations to build rapidly under favorable conditions. The insects have two generations annually in Massachusetts, with adults present throughout much of the year. Winter temperatures historically limited adelgid survival, but warming winters have enabled greater population persistence.
Common Mistake: Assuming all white material on hemlocks indicates adelgid infestation. Native elongate hemlock scale also produces white coverings but appears flatter and more elongated than the cottony masses of hemlock woolly adelgid. Confirm identification before treatment to avoid wasting resources on the wrong pest.
Other hemlock stressors accelerate mortality rates when combined with hemlock woolly adelgid, including elongate hemlock scale, hemlock looper caterpillars, spruce spider mites, hemlock borers, root rot disease, and needle rust. The adelgid invasion often delivers the final blow to trees already weakened by drought, poor site conditions, or other pest attacks.
The adelgid was probably brought to Massachusetts by migrating birds from infested hemlocks farther south, demonstrating how difficult preventing natural spread can be. Scientists are working with predatory beetles that feed on hemlock woolly adelgid in its native range, introducing these biological control agents to help manage populations in Massachusetts forests.
Systemic insecticides can protect high-value landscape hemlocks when applied by professionals. Treatment options include soil drenches and trunk injections that move throughout the tree to kill feeding adelgids. However, treating forest stands remains impractical due to cost and logistics, making biological control the most viable long-term management strategy.
5. Brown Marmorated Stink Bug
Brown marmorated stink bugs (Halyomorpha halys) invaded the United States from Asia and have established populations throughout Massachusetts. These shield-shaped insects feed on a wide variety of fruits and vegetables, causing significant damage to agricultural crops while also creating nuisance problems when they invade homes seeking winter shelter.
Adult brown marmorated stink bugs measure about three-quarters of an inch long with mottled brown coloring on their backs that provides excellent camouflage on tree bark. The smooth shoulder edge when viewed from above distinguishes them from native stink bug species that typically have pointed or spined shoulders. You’ll notice alternating light and dark bands on the antennae and along the edges of the abdomen.
These insects pierce plant tissue with their needle-like mouthparts to suck out juices, leaving behind damaged, unmarketable produce. On tree fruits like apples and pears, feeding creates corky, dimpled areas that extend beneath the surface, causing internal breakdown. Tomatoes, peppers, sweet corn, and soybeans all suffer similar damage when stink bugs feed during fruit or seed development.
The bugs remain active from spring through fall, with adults laying clusters of light-colored eggs on the undersides of leaves. Nymphs progress through five stages before reaching adulthood, appearing darker and rounder than adults in early stages. Multiple generations occur each season, with populations building throughout summer and peaking in late summer and early fall.
Pro Tip: Brown marmorated stink bugs seek shelter inside homes, attics, and wall voids during fall when temperatures drop. They enter through any available gaps around windows, doors, vents, and utility penetrations. Unlike some insects that reproduce indoors, stink bugs only overwinter inside—they don’t feed or reproduce until returning outdoors in spring.
Seal entry points before fall temperatures trigger the bugs’ search for shelter. Check window and door screens for tears, apply weatherstripping to doors, and caulk gaps around utility lines entering the building. Once inside, vacuum up stink bugs rather than crushing them to avoid releasing their characteristic pungent odor that gives them their name.
Outside, monitor gardens and orchards regularly during the growing season. The bugs feed preferentially on developing fruits and seeds, making mid to late summer the critical damage period. Surrounding vegetation can harbor populations that move into crops, so managing weeds around garden edges reduces nearby stink bug numbers.
Natural predators including parasitic wasps from the stink bug’s native range are being studied for biological control potential. However, these control agents have not yet been widely released in Massachusetts, leaving management dependent primarily on exclusion tactics for homeowners and limited insecticide options for commercial growers when populations reach damaging levels.
6. Winter Moth
Winter moth (Operophtera brumata) was initially introduced to North America from Europe via Nova Scotia sometime prior to 1950. While a predatory fly from its native range eventually provided effective control in Nova Scotia, winter moth remains a serious problem farther south, with more than 70,000 acres defoliated in a single year in Massachusetts alone.
You’ll spot male winter moths flying on mild evenings from late November through January, attracted to lights during their unusual cold-weather activity period. Males appear small and drab brown with a wingspan of about one inch. Females are nearly wingless with only small wing stubs, appearing grayish-brown and unable to fly. They climb tree trunks to lay eggs in bark crevices.
The pale green caterpillars emerge in spring just as tree buds begin opening, perfectly synchronized with leaf-out timing. This synchronization allows caterpillars to feed inside developing buds and on tender new leaves, causing more severe damage than later-season feeders. The caterpillars measure about one inch long when fully grown and move in a distinctive looping motion, earning them the alternate name “inchworms.”
Defoliation occurs during May and early June when caterpillars reach peak feeding size. Oak, maple, ash, crabapple, blueberry, and many other deciduous trees and shrubs suffer severe leaf loss. The caterpillars consume new leaves as they unfold, often leaving only leaf midribs and creating a lacy, skeletonized appearance across entire tree canopies.
Key Insight: Scientists introduced parasitic flies (Cyzenis albicans) from winter moth’s native Europe to provide biological control in Massachusetts. These flies lay eggs on foliage that caterpillars consume, with fly larvae developing inside the caterpillar and killing it. The biological control program has shown promising results in reducing winter moth populations across affected areas.
Trees can usually survive one year of complete defoliation by producing a second flush of leaves. However, repeated annual defoliation weakens trees significantly, reducing growth, making them vulnerable to other pests and diseases, and sometimes causing mortality. Blueberry crops suffer direct economic losses when winter moth strips developing fruit buds.
Sticky bands wrapped around tree trunks in fall can trap wingless female moths climbing up to lay eggs. Apply bands in November before moths emerge, placing them at chest height where females must cross to reach egg-laying sites. Check bands regularly and dispose of trapped moths in soapy water.
The caterpillars drop from trees on silk threads when disturbed, a behavior that helps them escape predators but also aids in dispersal to nearby trees and shrubs. You’ll sometimes notice caterpillars dangling from branches on these nearly invisible silk strands, especially on windy days when trees sway and disturb feeding caterpillars.
Monitor trees in spring when buds begin swelling. Early detection allows time to implement management strategies before caterpillar populations reach damaging levels. The biological control flies have significantly reduced winter moth populations in many Massachusetts communities, offering hope that this invasive pest may become less problematic in future years.
7. Lily Leaf Beetle
Lily leaf beetle (Lilioceris lilii) is an aggressive pest of lilies that chews holes and notches in lily leaves, stems, and buds throughout the growing season. This European native has established throughout much of Massachusetts, causing severe damage to both ornamental garden lilies and native wild lily species.
Adult lily leaf beetles display brilliant scarlet red wing covers (elytra) that make them unmistakable once you recognize them. They measure approximately one-quarter inch long with black legs, head, antennae, and undersides. When disturbed, the beetles often fall off plants and land on their black undersides while playing dead—a defensive behavior that makes them harder to spot against dark soil or mulch.
The beetles overwinter as adults in soil and leaf litter, emerging in spring when temperatures warm and lilies begin growing. After feeding and mating, females lay clusters of irregular orange-red eggs on the undersides of lily leaves. The eggs hatch into larvae that cause even more damage than adults, consuming leaves voraciously throughout their development.
Important Note: Lily leaf beetle larvae cover themselves in their own excrement, appearing as slimy, orange-brown blobs on lily leaves. This disgusting habit protects them from predators and makes them less appealing to handle, but removing them remains the most effective control method for home gardeners.
The larvae feed for two to three weeks before dropping to the soil to pupate. Adult beetles emerge about three weeks later and continue feeding on lilies through summer and fall. Multiple generations per year allow populations to build rapidly, with severe infestations completely defoliating lily plants and destroying flowers before they bloom.
All true lilies (Lilium species) and fritillaries (Fritillaria species) serve as hosts for lily leaf beetles, though the beetles show strong preferences for certain species. Asiatic, Oriental, and tiger lilies suffer particularly severe damage. The native Canada lily and wood lily face serious threats from this invasive pest in natural areas where they grow.
Handpicking adults and larvae provides effective control in home gardens. Check lilies daily during the growing season, especially focusing on new growth where beetles concentrate their feeding. Crush collected beetles and larvae or drop them into soapy water. The beetles may squeak when squeezed—a defensive behavior meant to deter predators.
Apply organic insecticides like neem oil or spinosad when populations overwhelm handpicking efforts. Target young larvae for best results, as they’re more vulnerable than adults or older larvae. Spray thoroughly to cover leaf undersides where larvae typically feed. Time applications to coincide with egg hatching for maximum effectiveness.
Clean up lily debris in fall to eliminate overwintering sites near lilies. The beetles shelter in soil, leaf litter, and plant debris close to where lilies grow, so removing this material forces them to search for winter shelter farther from next year’s plants. This simple sanitation practice reduces spring beetle numbers on emerging lilies.
8. Asian Tiger Mosquito
The Asian tiger mosquito (Aedes albopictus) has recently arrived in Massachusetts after moving through the Eastern United States from its original range in southeast and subtropical Asia. This aggressive mosquito capable of spreading West Nile Virus, Eastern Equine Encephalitis, and numerous other tropical diseases represents a growing public health concern as the species becomes more prevalent in the state.
You’ll recognize Asian tiger mosquitoes by the distinctive single white stripe running down the center of the head and back, with white banding on the legs that creates a striped appearance. These mosquitoes measure about one-quarter inch long, appearing noticeably black and white rather than the plain brown or tan coloring of many native mosquito species.
Unlike native mosquitoes that feed primarily at dawn and dusk, Asian tiger mosquitoes bite aggressively throughout daylight hours. They prefer biting humans and other mammals, readily entering homes and outdoor living spaces to find blood meals. The mosquitoes fly low to the ground, typically biting around ankles and lower legs, though they’ll bite any exposed skin.
Pro Tip: Asian tiger mosquitoes breed in small artificial containers that hold water for just a few days, including bottle caps, flower pot saucers, bird baths, clogged gutters, tires, and any item that collects rainwater. This breeding strategy differs from native mosquitoes that typically require larger, more permanent water bodies, making container removal the most effective control method.
Larvae develop rapidly in container water, completing their life cycle from egg to adult in as little as seven to ten days under warm conditions. Females lay eggs just above the water line in containers, with eggs hatching when water levels rise from rain or watering. This egg-laying strategy allows populations to build quickly following summer rains.
As winter temperatures increase due to climate change, the species is likely to become more prevalent throughout Massachusetts and the Northeast. The mosquitoes are limited by cold winter temperatures, but warming trends enable more consistent overwintering and earlier spring emergence, extending the season when mosquitoes pose health risks.
Empty, cover, or remove any containers that collect water around your property. Change water in bird baths and pet bowls at least twice weekly. Clean gutters regularly to prevent standing water accumulation. Store items that could collect water upside down or under cover. These simple actions eliminate breeding sites near your home.
Use EPA-registered insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus when spending time outdoors. Apply repellents according to label directions, reapplying as recommended to maintain protection. Wear long sleeves and pants when possible, especially during peak mosquito activity hours.
Screen windows and doors to prevent mosquitoes from entering your home. Repair torn screens promptly and ensure screens fit tightly in frames without gaps. Use air conditioning when possible, as closed, cooled spaces exclude mosquitoes while providing comfortable indoor environments during summer months when mosquito populations peak.
9. Japanese Beetle
Japanese beetles (Popillia japonica) attack more than 300 plant species including roses, grapes, hops, and numerous landscape plants throughout Massachusetts. Both adult beetles and larvae cause significant damage—adults skeletonizing leaves on ornamental plants while larvae destroy grass roots, creating dead patches in lawns.
Adult Japanese beetles measure about half an inch long with distinctive metallic green bodies and copper-colored wing covers. Five small patches of white hair appear along each side of the abdomen where it extends beyond the wing covers, with two larger white hair patches on the rear end. These white hair tufts provide the most reliable identification feature when observed from above or behind.
The beetles emerge from soil in late June and remain active through August, feeding on plant foliage during warm daylight hours. They skeletonize leaves by consuming the tissue between veins, leaving behind a lacy network of veins that turns brown and dies. Heavily infested plants can lose all leaf tissue, appearing burned or diseased despite the actual cause being insect feeding.
Key Insight: Japanese beetles aggregate while feeding, releasing pheromones that attract other beetles to the same plant. Finding one beetle often means finding dozens, with mass feeding events capable of defoliating plants rapidly. This aggregation behavior makes beetle management challenging, as treating one plant may simply attract beetles from nearby untreated plants.
The larvae—white C-shaped grubs measuring up to one inch long—feed on grass roots from late summer through the following spring. You’ll recognize Japanese beetle grubs by three pairs of legs near the head and a distinctive V-shaped pattern of spines on the raster (rear end) when viewed under magnification. The grubs overwinter deep in the soil, moving closer to the surface to resume feeding in spring.
Lawn damage appears as brown, dead patches that pull up easily like carpet since roots have been consumed. Birds, skunks, and raccoons often dig up infested lawns searching for grubs, creating additional damage. Peak grub feeding occurs in spring before beetles emerge, making spring the optimal time to detect and manage lawn infestations.
Handpicking adult beetles from plants early in the morning when they’re less active provides effective control in small gardens. Drop collected beetles into soapy water to kill them. Focus on new beetle arrivals before pheromones attract large aggregations that become overwhelming to manage manually.
Avoid Japanese beetle traps that use pheromone lures to attract beetles. Research shows these traps attract more beetles to your property than they capture, increasing feeding damage on nearby plants. The traps work as advertised for catching beetles, but they simultaneously make your landscape a magnet for beetles from surrounding areas.
Treat lawns with beneficial nematodes or milky spore disease to control larvae biologically. Apply nematodes in late summer when small grubs are present and soil temperatures remain warm enough for nematode activity. Milky spore establishes more slowly but provides longer-term control as the bacterial spores build up in soil over multiple years.
Conclusion
Your observations serve as the first line of defense against invasive insect threats in Massachusetts. The Outsmart Invasive Species Project provides free tools that transform any smartphone into a reporting device, enabling you to document and report invasive insects whenever you encounter them during daily activities.
Download the Outsmart Invasive Species app through iTunes or Google Play to report invasive species anytime. The app guides you through the documentation process, captures GPS coordinates automatically, and submits reports directly to researchers and forest health specialists who track invasive species across the state. You can also register to submit data using the free Early Detection and Distribution Mapping System (EDDMapS) at Outsmart on EDDMapS.
When you find a suspected invasive insect, note your exact location using physical address or GPS coordinates, record the date of observation, and take clear, in-focus photographs from multiple angles. Collect a specimen if safe to do so, but photograph it first in case the insect escapes. These details help experts confirm identification and track the species’ spread across Massachusetts.
Early detection and continual monitoring remain key to stopping new invasive threats before they establish and spread, whether in forests or city neighborhoods. The Worcester Asian longhorned beetle outbreak demonstrates both the devastating costs of established invasions and the effectiveness of rapid response when infestations are detected early. Your reports contribute directly to protecting Massachusetts forests and landscapes for future generations.
Never move firewood between locations, as transported firewood represents the primary spread mechanism for numerous invasive insects. Buy firewood where you’ll burn it, gathering on-site when camping in state forests or parks. This simple practice prevents accidentally introducing emerald ash borers, Asian longhorned beetles, and other wood-boring insects to new areas.
Scientists and forest managers work continuously to protect Massachusetts forests by monitoring for invasive species and applying biological control methods when appropriate. Parasitic flies for winter moth, predatory beetles for hemlock woolly adelgid, and other natural enemies from these insects’ native ranges offer hope for long-term management without constant chemical applications.
Report suspected invasive insects to UMass Extension with photographs and location details. Early reporting enables rapid response that can mean the difference between containing a small infestation and facing a multi-million dollar eradication program. Your vigilance today protects the forests, gardens, and urban landscapes that define Massachusetts for decades to come.
