Are Lanternflies Coming Back? What to Expect This Season

Spotted lanternflies are not going away. Every spring since their first detection in southeastern Pennsylvania in 2014, the insects have hatched in growing numbers across an expanding range in the eastern United States, and this season will follow the same pattern. The eggs that females cemented onto trees, stones, and outdoor furniture last fall are already beginning to hatch in warmer areas, and new research shows these egg masses can survive far colder winters than scientists initially assumed. Understanding the timing, the damage potential, and the realistic options for managing them can help you prepare rather than just react.

When They Hatch and What Drives the Timeline

Spotted lanternfly eggs do not hatch on a calendar date. Their emergence tracks accumulated warmth, measured in degree-days above a base temperature of about 10.4°C (roughly 51°F). Researchers modeling egg hatch across Pennsylvania and Virginia found that this base temperature reliably predicted when nymphs would appear across different locations and years.¹ In practical terms, that means hatch starts earlier in the Mid-Atlantic than in, say, upstate New York, and a warm March can push the whole cycle forward by weeks.

Once nymphs emerge, they pass through four stages before becoming adults. The first tiny black nymphs appear after about 270 cumulative degree-days above 10°C, while adults don’t show up until roughly 1,112 degree-days have accumulated from January 1.² In southeastern Pennsylvania, that translates to first nymphs in late April or May and adults arriving by midsummer, with egg-laying peaking in the fall. Researchers found that the timing of nymphal stages is well predicted by degree-days counted from January 1, but for adult activity and egg-laying, a better starting point is the date adults are first spotted in a given area.³

What this means for you: if you live where spotted lanternflies were present last year, expect to see tiny black nymphs on plants and outdoor surfaces once your area has had several weeks of sustained warmth. The adults with the showy red-and-black wings will follow later in summer. If you’re checking for egg masses on trees or outdoor equipment, early spring before hatch is the window for scraping them off.

Cold Winters Are Not Stopping Them

A common hope is that a harsh winter will kill off most of the eggs. The evidence says otherwise. Cold-tolerance experiments found that spotted lanternfly eggs hatched successfully even after extended exposure to temperatures below −20°C (−4°F). The estimated lower lethal temperature for egg masses is around −27.7°C (roughly −18°F), which is far colder than typical winter lows across most of the eastern United States and even much of southern Canada.⁴ Hatch rates did drop when eggs experienced temperatures at or below −20°C for short periods, and below −15°C during prolonged cold snaps, but the fact that any eggs survived at all at those extremes is the troubling part. Low winter temperatures alone are unlikely to limit the insect’s range in many parts of North America.⁵

This upends earlier assumptions that cold northern climates would act as a natural brake on the insect’s spread. Areas that were once considered climatically unsuitable may still be at risk if egg masses arrive on shipped goods or vehicles.

How They Keep Spreading to New Areas

Spotted lanternflies are mediocre fliers. They can hop and glide short distances, but the dramatic expansion across the eastern U.S. is not driven by flight. Modeling of the insect’s spread dynamics showed that human-mediated dispersal, primarily via cars, trucks, and trains, is the dominant factor. When researchers incorporated even very modest rates of hitchhiking, as few as three successful long-distance movements per year, their model accurately predicted over 92% of the counties where the insect had actually been detected.⁶

This is why quarantine zones, vehicle inspections, and public awareness campaigns keep expanding. The egg masses are flat, roughly one to two inches long, and coated in a putty-like substance that weathers to a cracked, grey appearance. They are commonly found on wheel wells, pallets, firewood, and outdoor furniture. A single overlooked egg mass on a delivery truck can seed a population hundreds of miles from the nearest known colony. If you live outside the current range but receive shipments from infested areas, checking for egg masses on packaging and vehicles is one of the most practical steps you can take.

Where the Range Is Headed

Climate-suitability models paint a broad picture. One recent analysis found that suitable habitat in North America overlaps with every county where tree of heaven, the insect’s preferred host, already grows, and with nearly all designated grape-growing regions in the U.S., excluding only the Central Valley of California in particularly hot years.⁷ A separate global modeling effort projected that the central and eastern United States, along with southern Europe, remain the most climatically favorable zones outside the insect’s native range in East Asia. The strongest environmental predictor of where it can establish was the mean temperature during the driest quarter of the year.⁸

In short, most of the eastern seaboard, the Midwest, and parts of the Pacific Northwest have climates that could support the insect. The speed at which it arrives depends more on human traffic patterns than on anything ecological.

The Tree of Heaven Connection

Spotted lanternflies feed on more than 70 plant species, but tree of heaven (Ailanthus altissima) plays a disproportionately large role in their life cycle. When lanternflies had access to both grapevines and tree of heaven, they developed faster, laid more eggs, weighed more, and survived at higher rates than those fed on grape alone or tree of heaven alone.⁹ That mixed-diet advantage makes landscapes where tree of heaven grows near crops especially vulnerable. It also means that removing tree of heaven from the vicinity of vineyards or orchards is one of the more effective management steps. Concord grapevines alone turned out to be a poor-quality food source, but the presence of tree of heaven nearby essentially supercharged the insect’s fitness above what either plant provided on its own.

During the egg-laying season, females strongly prefer tree of heaven for oviposition. Research tracking egg mass placement found that taller trees with larger root-collar diameters attracted significantly more egg masses.¹⁰ If you have large tree of heaven specimens on or near your property, they are likely serving as egg-mass nurseries each fall. Removing or treating these trees before egg-laying season can cut local populations substantially, though it needs to be done carefully because lanternflies will shift to alternative hosts if only some trees are removed.

What the Damage Actually Looks Like

Spotted lanternflies feed by piercing plant tissue and drinking phloem sap, the sugar-rich fluid that carries nutrients through a plant. They excrete large quantities of sticky honeydew that coats surfaces beneath feeding sites and promotes the growth of sooty mold, which blackens leaves, decks, and cars alike.¹¹ The mold is mostly a cosmetic nuisance on hard surfaces, but on leaves it blocks sunlight and reduces the plant’s ability to photosynthesize.

The real agricultural concern is grape production. Prolonged feeding by large groups of adult lanternflies, particularly at densities of eight or more per grapevine shoot, depleted starch reserves in the roots and strongly reduced gas exchange in the leaves. Researchers concluded that heavy late-season feeding can induce carbon starvation in the vine, with the potential for lingering harm the following growing season as well.¹² At lower densities, around four or fewer per shoot, effects were minimal, which means the damage is highly density-dependent. A handful of lanternflies on a backyard vine is annoying; a swarm of hundreds can seriously compromise the plant.

An economic assessment for New York State estimated that if lanternfly infestations in the Lake Erie and Finger Lakes grape-growing regions went unmanaged, losses could reach about $1.5 million in the first year, climbing to roughly $4 million by the second year and $8.8 million by the third.¹³ Those figures assume growers are unprepared and not actively managing the pest. Early detection and response can blunt those numbers considerably, which is why extension services have been pushing awareness campaigns in grape-growing counties.

Damage to Hardwood and Urban Trees

Grapes get the most attention, but lanternflies also stress common shade and hardwood trees. A four-year feeding study found that sustained lanternfly pressure significantly reduced trunk diameter growth and depleted starch stored in the roots of young silver maples, weeping willows, river birches, and tree of heaven. The damage scaled with insect density: more lanternflies feeding on a tree meant more growth suppression.¹⁴

Even short-term feeding by late-stage nymphs on young silver maple trees reduced soluble sugars in leaves and branch wood, and trunk diameter growth dropped by more than half during the following growing season.¹⁵ That lag effect is important: the tree may look fine during the season when feeding occurs, only to show poor growth the next year. Nurseries growing young stock and municipalities managing street trees in infested areas should factor this delayed impact into their planning.

Natural Enemies and Biological Control

One piece of encouraging news is that native pathogens have begun attacking spotted lanternfly populations. In 2018, researchers documented co-occurring outbreaks of two fungal pathogens, Batkoa major and Beauveria bassiana, killing lanternflies in northeastern North America.¹⁶ Dead lanternflies infected with these fungi are sometimes visible clinging to tree trunks with a white fuzzy coating. Whether these fungi can suppress populations enough to make a meaningful dent remains an open question, as the outbreaks seem to be patchy and weather-dependent.

Various native predators, including birds, spiders, and predatory insects, have been observed feeding on lanternflies, but none appear to be specialized enough to keep populations in check. Research into classical biological control, which involves importing natural enemies from the insect’s native range in Asia, is ongoing. A parasitoid wasp, Anastatus orientalis, that attacks lanternfly eggs in China has been studied in quarantine facilities in the U.S. These efforts are still in early stages and any field release would require years of safety testing. In the near term, biological control will supplement other methods, not replace them.

Trapping and Monitoring Advances

Detecting lanternflies early in a new area is critical, and better lures are helping. Researchers identified three plant-derived chemicals that attract spotted lanternflies: methyl salicylate, (Z)-3-hexenol, and (E,E)-α-farnesene, all of which are released by tree of heaven and grape. Of the three, methyl salicylate was attractive to all life stages and produced a two- to four-fold increase in trap captures compared with unbaited traps in the field, with stronger responses at higher doses.¹⁷

More recently, scientists discovered that lanternflies also use a complex pheromone system involving compounds from both honeydew and body odors to locate each other for mating and egg-laying.¹⁸ Combining plant-based attractants with pheromone components could eventually lead to traps effective enough for population suppression, not just detection. For now, commercially available circle traps and sticky bands wrapped around trees remain the most accessible tools for homeowners. If you use sticky bands, wrapping them in a wire cage helps prevent non-target catches of birds and small animals.

What You Can Do This Season

Most management guidance boils down to a few practical actions, timed to the insect’s life cycle. In late winter and early spring, inspect outdoor surfaces for egg masses, which look like dried smears of mud, and scrape them into a container of rubbing alcohol or hand sanitizer. Through spring and early summer, watch for small black nymphs with white spots on the undersides of leaves, railings, and any smooth surface near trees. By midsummer, the older nymphs gain red patches and are easier to spot. Adults with their distinctive grey forewings and red hindwings appear from mid to late summer and persist into late fall.

Contact insecticides applied to tree trunks and systemic treatments injected into trees can reduce feeding pressure, especially on high-value plants like grapevines and ornamental trees. Removing tree of heaven within a reasonable radius of crops or garden plants reduces the local food supply and egg-laying habitat. Some vineyard managers have adopted a “trap tree” strategy, leaving one or two treated tree of heaven specimens standing to draw lanternflies away from vines and then killing the insects concentrated on those trees.

Reporting new sightings to your state’s department of agriculture remains one of the most impactful things any individual can do. Early detection of new satellite populations is what allows rapid-response teams to contain outbreaks before they become entrenched. Many states now have reporting apps or online portals that take less than a minute to use. Given how effectively these insects hitchhike on vehicles and freight, a new population can establish far ahead of the advancing front, and the people most likely to notice are ordinary residents who know what to look for.