Spotted Lanternfly Management for Landscape Professionals

Introduction

Spotted lanternfly (SLF), Lycorma delicatula, is an invasive planthopper that was first detected in North America in 2014 in southeastern Pennsylvania. It is native to parts of Asia. As of April 2021, SLF is found in Pennsylvania, New Jersey, New York, Connecticut, Virginia, West Virginia, Maryland, Delaware, and Ohio. SLF has also been detected in Massachusetts, Maine, Michigan, Oregon, California, and North Carolina, although established populations are not known to exist in these states.

SLF feeds voraciously on many economically important crops like grapevines, hops, ornamental nursery plants, and several tree species. Heavy SLF feeding has contributed to the death of grapevines, the invasive tree Ailanthus altissima (tree-of-heaven, or TOH), and black walnut saplings. While SLF feeding can stress plants and cause localized branch damage, it has not been seen to directly kill other plants. SLF feeding is considered a plant stressor and may contribute to the long-term weakening of established plants and trees. It is currently considered to be primarily a nuisance pest in ornamental landscapes.

To protect vulnerable plants and industries, it is important to avoid spreading SLF to new areas. Many affected states have enacted quarantine orders to prevent accidental human-assisted spread of SLF. The quarantine orders require any items being moved from known infested areas be inspected and SLF destroyed before shipment. The quarantines affect all residents and businesses. All businesses conducting operations in Pennsylvania are required to get an SLF permit. Complying with the quarantine requires businesses to document their inspections and actions to prevent accidental spread. Additional costs associated with controlling SLF in plant production nurseries, vineyards, shipping facilities, and other businesses, in combination with costs to inspect items being shipped, have been identified as being significant by many business owners and operations managers.

Life Cycle and Identification

There is one generation of SLF per year in Pennsylvania (Figure 1). The eggs are laid in the fall (September to November) and hatch in the spring (late April to June; 50 percent hatch at ~225 GDD at base temperature 10.4°C; see the Penn State Extension Spotted Lanternfly Egg Hatch Prediction Map). Egg masses are laid on many surfaces (trees, decks, houses, outdoor equipment, rocks, etc.) and protected with a mud-like covering. Each egg mass contains an average of 35 to 40 individual eggs. After hatching and before reaching adulthood, SLF goes through four nymphal stages called instars. Newly hatched nymphs are small (~1/8 inch) and can be hard to find, often being mistaken for small ticks or spiders. With each molt to the next instar, the nymphs roughly double in size. The first three instars are black with white spots. The last (fourth) instar is red with white dots and black stripes and roughly 1/2 inch long. SLF nymphs and adults are strong jumpers. In Pennsylvania, SLF adults begin to emerge in July (50 percent at ~1,100 GDD at base temperature 10.4°C) and remain active as adults until they are killed by the first hard freeze in the late fall. Adults are the most obvious and easily detectable stage because they are large (about 1 inch) and highly mobile. Adults have black bodies. Their forewings are gray with black spots, and the tips are black with gray veins, while their hindwings are red, black, and white. Only the adults have wings and can fly. However, because SLF adults walk more than fly, their wings often remain closed, leaving only the forewings visible. This makes them more difficult to identify in low numbers, from a distance, or when they are high in a tree.

Figure 1. Life stages of spotted lanternfly

B. Early nymph (actual size = 1/8") Found late April-July. Photo credit: PA Department of Agriculture

C. Late nymph (actual size = 1/2") Found July-September. Photo credit: PA Department of Agriculture

D. Adult, wings closed (Actual size = 1 inch) Founds July-December. Photo credit: PA Department of Agriculture

E. Adult, wings open. Photo credit: PA Department of Agriculture

Feeding Damage

SLF feeds on plant sap (which is contained in the phloem tissue) using a piercing-sucking mouthpart (Figure 2). They acquire nutrients from the plant sap and also rely on associated bacteria in their guts to support their nutritional requirements. The sap they ingest contains high amounts of carbohydrates (sugar), which is not completely digested by the insect. They excrete the excess as a waste substance called honeydew, which can build up below the feeding insects. On sunny days, honeydew can be seen falling from trees, resembling a light rain. Honeydew is attractive to ants, wasps, bees, and other sugar-loving insects.

Figure 2

As the honeydew accumulates, it is often colonized by sooty mold (fungi). Sooty mold does not directly harm plants or the surfaces on which it grows, but it does block photosynthesis in affected plant leaves. With dense groupings of SLF, understory plants may die because of the sooty mold buildup on their leaves. Sooty mold frequently stains objects such as tree trunks, decks, patios, and vehicles that are underneath affected trees. These stains can be very difficult to remove.

Consequences of direct feeding damage by nymphs and adults to the host trees vary greatly by host species, numbers of SLF feeding, and environmental conditions. Death of some TOH and branch dieback on other ornamental trees has been reported in cases of high infestation levels. Some physical damage beneath the bark on branches following heavy feeding has been observed and is being further studied. Based on experiments in 2019 and 2020, we found that high levels of adult SLF feeding can reduce the photosynthetic activity of some trees. It is possible that after heavy feeding, multiple years of sustained damage, or in particularly dry years, SLF may cause significant damage to ornamental and shade trees.

Seasonal Host Preference

SLF has an extremely broad host range and has been recorded feeding on over 70 different plant species. Conifers are generally not considered to be good hosts for SLF. Despite their broad host range, some plants appear to be more favorable to SLF than others, and host preference has been linked to life stage. Numerous variables appear to determine the attractiveness of a particular plant, the most important being what plant species are available or absent in the nearby landscape. Additional factors include the health of the plant, time of year, the SLF population size, and how long SLF has been present in the area. Nymphs, in particular, have an especially large host range that includes perennials and any new and tender plant growth, whereas adults seem to depend more on certain hosts, primarily woody stems of trees and mature vines.

We emphasize that not every tree needs to be treated. Researchers have repeatedly observed strong host preference for specific tree species, though the exact trees will be dependent on the surrounding landscape. In 2020, more than 200 trees were counted for SLF in a 0.1-square-mile shopping center. While only 31 percent of the trees were red maples, they held over 94 percent of the SLF population (Figure 3). Scout the area first and then consider treating if high populations are found and persist.

Figure 3

Table 1 represents the key plant hosts of SLF and the time at which they are most likely to be found on these hosts; it does not represent a comprehensive list of what SLF feeds on, but rather the patterns of SLF feeding that have been observed through the season. As plants begin to senesce at the end of the growing season, they are less likely to serve as hosts for SLF. The patterns of host use may change with varying weather conditions, by region, or due to other factors as yet undetermined.

Please note that while TOH (Ailanthus altissima) is a strongly preferred host, it is not a required host in the development of SLF. However, preliminary evidence suggests that access to TOH may speed SLF development time and improve fitness. Access to multiple host plant species rather than a single host species, regardless of TOH availability, has also been shown to improve fitness.

Table 1. Common plant hosts for spotted lanternfly throughout the season.

Monitoring

Home gardeners have reported SLF nymphs feeding on cucumber, basil, rose, peony, Russian sage, and many more plants. In some cases, damage to these plants has been reported when SLF populations are high. SLF nymphs generally feed on herbaceous plants for only a short period of time (less than one week) and then move to other plants. We recommend monitoring high-value plants on a regular basis to observe where SLF is feeding and to determine if they have moved to or from a specific plant. If there are favorite host plants nearby, we recommend you focus monitoring and potential treatment on those plants. You can monitor with traps (see below) or through periodic visual inspection.

Population Fluctuations

In newly infested areas, SLF populations tend to increase steadily over several seasons, and preferred individual host plants tend to remain consistently favored from year to year. However, observations of populations near the original introduction indicate that numbers can drastically drop or rebound from season to season. It is believed that population density, host fitness, natural enemies, and weather conditions play a role in these fluctuations, but further research is needed. Unfortunately, after a season of low population numbers, it is not uncommon to see an increase in population the following year. In some cases, population numbers may not increase until the late fall in a particular neighborhood, just prior to egg laying, making preemptive treatment timing very difficult. Distance traveled by individual insects in the course of a season is not yet known, but it is suspected to be miles.

Management

It is important to understand that SLF cannot be prevented from coming onto any one property. SLF adults tend to fly to new trees to feed in the late summer. Properties in areas with high populations of SLF can experience sudden increases in populations of nymphs, but this occurs more commonly with adults. While we are currently working to develop biological and cultural management practices for SLF, the most effective control measure to date is the use of insecticides. Table 2 provides a quick reference of roughly when control options should be employed.

Table 2. Management options for spotted lanternfly throughout the year.

Biological Control

Currently, there are no known natural enemies of SLF that are expected to reduce populations in the United States. Some generalist predators (spiders, praying mantises, parasitoids, birds, etc.) will attack and eat SLF. Additionally, two species of fungal pathogens were identified in Pennsylvania that can attack and kill SLF. One species, Beauveria bassiana, was the focus of recent research. This pathogen is commercially available as a biorational insecticide. In 2020, we evaluated the efficacy of B. bassiana in infested woodlots. So far, these test applications have not shown effective control of the local population. We do not currently recommend B. bassiana for management of SLF; however, continued research may lead to optimizing the use of B. bassiana for inclusion in future recommendations. Researchers are exploring the native range of SLF to search for natural enemies for potential release in the United States. These efforts are currently under evaluation in USDA quarantine facilities.

Cultural Control

Removing Preferred Host Plants

Removal of preferred host plants has not been specifically evaluated for success in managing SLF populations, but removing certain trees can prevent honeydew and sooty mold accumulation on property beneath infested trees. If possible and practical, we recommend removal of TOH. It is invasive in the United States and has other negative environmental effects. When removing TOH, use an herbicide to kill the root system (see Tree-of-Heaven for more information). However, removal of TOH or other host plants is unlikely to consistently reduce SLF numbers. In addition to removal, some male TOH can also be left alive and treated with a systemic insecticide to kill SLF as they feed. TOH is a dioecious plant, meaning there are separate male and female trees. If allowing some trees to remain, keep and systemically treat only the male trees where possible, in order to prevent females from reseeding the area.

Using Traps

Traps can capture and kill SLF on individual trees. Trapping is a mechanical control method that does not use insecticides. You may catch a lot of SLF with a trap, but because they move around in the landscape, trapping will not prevent more SLF from coming to that tree. Also, because we do not yet understand how different amounts of SLF feeding affect the health of specific trees, there is currently no way to determine if trapping SLF will have a significant protective effect. Be aware that this method will probably not significantly reduce the greater population of nymphs outside of the trap area, nor will it likely reduce the number of adult SLF you see later in the year.

Traps are used to intercept SLF nymphs and adults as they crawl up the tree trunk. We suggest setting traps as soon as SLF hatch (late April through June). Traps can capture large numbers of nymphs. While adult SLF can also be captured by tree traps, they may avoid them, resulting in less effectiveness later in the season. Two types of traps are often used to capture SLF: sticky bands and a funnel-style trap called a “circle trap.”

Sticky Bands

Sticky bands capture SLF in sticky material as they move up the tree. Several types of sticky bands are available for purchase online or from your local garden center.

Sticky bands have a major drawback: the sticky material can capture other insects and animals, including birds, small mammals, pollinators, butterflies, and more. To reduce the possibility of bycatch, a wildlife barrier of vinyl window screening or other protective material must be installed (Figure 4). Sticky bands deployed without a wildlife barrier are not recommended. A barrier made of chicken wire is not as effective because it can allow beneficial insects and small birds to pass through. Secure the screening to the tree above the sticky band with pushpins and leave it open at the bottom. It should extend several inches above and below the sticky band and be close to the tree at all points to prevent larger creatures from flying or climbing underneath. If you decide to use sticky bands, check them regularly (every day if possible). If you capture an animal, do not attempt to free it by yourself—you may put the animal and yourself in danger. If you wish to try to save the animal, cover any exposed sticky material with plastic wrap or tissue paper to reduce additional entanglement, remove the band from the tree as carefully as possible, and take the animal to a wildlife rehabilitation center. To find a center, see the Pennsylvania Association of Wildlife Rehabilitators website.

To date, we have not found that any commercially available sticky band is more effective at catching SLF than another. There is also a commercially available band that uses a white fiber material to hold the inward-facing sticky side of the band away from the trunk of the tree. This creates a protected sticky surface that reduces the potential of catching birds and other animals. Homemade bands using products like duct tape or petroleum jelly on water-resistant paper are less effective than commercially available sticky bands because they lose their stickiness easily and can allow SLF to escape.

Figure 4

Circle Traps

A circle trap consists of a funnel-shaped piece of screening material that directs SLF into a collection container at the top (Figure 5). Circle traps do not use any sticky material. Much less capture of nontarget insects and animals has been observed in circle traps compared to sticky bands. You can purchase circle traps or build them yourself. For a detailed guide on how to build a circle trap, see “How to Build a New Style Spotted Lanternfly Circle Trap.” Some people have built similar traps, devising a range of methods that work. Building these traps is a good project for anyone who wants to kill SLF while saving money by using materials they may already have on hand.

Figure 5

Installation

Traps work best on trees with smooth bark; bark with deep grooves may allow SLF to crawl underneath the trap. Place the trap about 4 feet from the ground and secure it tightly against the tree by wrapping the material tightly and using pushpins or staples to attach it to the thickest bark on the tree. Avoid using nails or anything that would wound the green, living tissue underneath the bark. Only set up traps on trees on your property or where you have permission to do so. Remember to remove all parts of the trap at the end of the season to reduce damage to the bark and eliminate pollution.

Finding and Destroying SLF Eggs

Female SLF will lay their eggs in a variety of places and on a wide range of surfaces. One common place to find eggs is on or near trees where females were feeding during the egg-laying period in the late fall. Tree hosts preferred by SLF during the late fall include red maple, silver maple, and willows—these trees are an excellent place to start looking for egg masses. However, SLF will also lay eggs on other trees on which they do not typically feed, including black cherry, pine, and others. They will also lay eggs in protected areas (generally on the undersides) of rocks, lawn furniture, decks, fences, rusty metal, and many other surfaces.

SLF eggs can be destroyed by scraping them from the surface where they were laid into an alcohol solution (e.g., rubbing alcohol or hand sanitizer) where they should be left permanently. Eggs can also be destroyed by thoroughly squishing or “popping” them.

It is important to keep in mind that you will not be able to reach all the egg masses deposited on a tree. Researchers have documented that, on average, less than 2 percent of the egg masses laid on test trees were at a reachable height (up to 10 feet from the ground), leaving 98 percent of the egg masses above reach. We do not recommend using ladders or climbing trees to get to the unreachable eggs.

Each destroyed egg mass can remove up to 50 SLF from the next year’s generation, but you are unlikely to destroy all SLF in an area. Continued management strategies may be necessary the following year.

Chemical Control

Ovicides to Kill Egg Masses

Experiments have shown that some insecticide sprays can kill SLF eggs. So far, all experiments were done between February and April using egg masses that had intact protective coverings. The most effective ovicides tested that are registered to use on ornamentals were horticultural and dormant oils. When oils were applied directly to the egg masses at a concentration of at least 3 percent, they were effective in killing up to 75 percent of treated eggs. The only plant-based oil tested was soybean oil, which had similar control of SLF egg masses when applied at a 50 percent concentration in one preliminary test.

These experiments suggest that registered insecticidal oils may provide some control of eggs if they are applied between February and April in high enough volumes to get excellent coverage. Oils not only offer a lower toxicity option but may provide some control for egg masses that are not accessible for scraping or smashing. However, for egg masses that are within a reachable area, scraping or smashing will provide greater efficacy than currently available ovicides. We are actively researching other ovicides that could provide increased control.

Contact Insecticides

Many commonly available insecticides that kill insects on contact are effective against SLF. If you are trying to control SLF for the entire season using only insecticides with contact activity, repeat applications may be needed because contact insecticides vary in their residual effectiveness and new SLF will continue to move onto preferred plants.

Efficacy and toxicity vary among insecticide products. We recommend trying the least toxic options first. Toxicity to mammals can be determined from the LD50 values found on the Safety Data Sheet (SDS) for each product. Toxicity to birds, fish, and bees for some active ingredients can be found in Table 3. Apply contact insecticides only after bloom is finished to protect beneficial pollinating insects.

N = nontoxic; S = slightly toxic; M = moderately toxic; H = highly toxic; — = data not available.
*Some products may have organic labeling.
This table is based on the experiments we have done to date and should not be considered final or complete. The contact insecticides can include spraying on trunk, branch, and foliage.

Systemic Insecticides

Systemic insecticides are translocated through the plant after application via the plant’s vascular system. This process provides efficacy by killing feeding insects that are exposed to the insecticide in the tissues and sap. The duration of efficacy is generally much longer than that of contact insecticides, but it does not expose nontarget organisms that are not feeding on the plant to the insecticide. Four application methods are used to apply systemic insecticides to be taken up by the plant: trunk injection, trunk spray, soil drench and injection, and foliar application. Not all products are labeled for all application methods. Insecticide residue can contaminate flowers, so it is important to apply systemic insecticides only after bloom is finished to protect pollinators and other beneficial insects.

To control adult SLF in landscapes, systemic insecticides containing either dinotefuran or imidacloprid are suggested only for high-value trees and in areas with high SLF populations. Research trials are ongoing to evaluate the efficacy of these active ingredients, different application methods, and timing, and to determine how much insecticide is needed to control SLF and how long the treatment will last.

Always read the label and apply the pesticide according to the directions. Certain products and/or applications may have restrictions on the cumulative amount of pesticide applied per designated timeframe or acreage. It is illegal to exceed limits of product use that are specifically stipulated by the label. This is true even if adequate control has not been achieved due to the variables noted above. Table 4 provides information on systemic products for spotted lanternfly adults.

Trunk Injection

SLF death has been observed in less than 24 hours after injecting a tree with dinotefuran. Injections of imidacloprid have also been successful but take longer to become effective. Trunk injection can provide the most accurate dosing of a tree, often with the least amount of material used, as very little material is lost to the environment outside of the tree. Products labeled for trunk injection may not have restrictions of volume of active ingredient amount per acre per year and can allow more trees per acre to be treated without violating the label restrictions. Be sure to follow the insecticide label and equipment manufacturer’s instructions. As with other application methods, the environmental conditions and vascular health of the tree can greatly affect the translocation speed of the insecticide.

Trunk Spray

Trunk sprays (also referred to as “bark banding” or “bole sprays”) with dinotefuran have also been successful. Observed death of SLF may take longer by trunk spray than with injected applications but is still likely to occur within a few days of treatment. If the label requires a bark penetrant as a spray adjuvant, be sure to include it in your application. It is important to properly dose the trees based on size measurement, not simply “spray until runoff.” It is often necessary to pause the application to wait for the material to be absorbed before resuming the application so that the full dose dictated by tree diameter at breast height (DBH) may be applied without runoff. Large trees with exfoliating bark, such as mature silver maples, may be difficult to properly treat with this method because the bark can reduce the penetration of the insecticide into the living tissue. Additionally, trees that are wounded and have a compromised vascular system may not be able to translocate the insecticide.

Soil Drench and Soil Injection

Soil drench application is commonly used for SLF, especially for systemic imidacloprid formulations that are widely available to home gardeners. Soil injection by plant health professionals with specialized equipment can provide more precise application than soil drenching, but it also relies on applying a water-soluble insecticide to the root zone of an individual plant. Little efficacy data from soil drench or soil injection applications of imidacloprid to control SLF is available. The insecticide needs time to be taken up by the tree roots, giving this method the greatest time delay until it begins to kill SLF. Dinotefuran soil drenches tend to be taken up, and provide efficacy, much faster and more consistently than imidacloprid due to its higher water solubility. In general, soil drenches and soil injections are less precise than trunk sprays or trunk injections. The amount of water needed to carry the insecticide into the tree is also very important. Postbloom applications of imidacloprid soil drenches are recommended in the spring, whereas dinotefuran should be applied midsummer through September to target adult SLF. Read the label carefully and follow the directions to achieve best results. Be aware that imidacloprid binds easily to organic matter, allowing it to remain in some soil types for long periods of time; in some cases, this may mean trees are dosed with imidacloprid in successive years after an initial soil drench, which could contaminate flowers and affect pollinators. By contrast, dinotefuran and its degradate MNG are highly soil mobile, which provides for fast uptake but also increases the risk of water-table pollution, especially in areas of sandy soil or shallow water tables.

Foliar Application

Foliar applications with appropriately labeled systemic products can provide rapid efficacy for the control of SLF. Generally, this application method provides the lowest dose of systemic active ingredient to individual trees compared to the other methods discussed and thus also provides the shortest duration of residual efficacy. Foliar applications with systemic products have the greatest potential to impact nontarget organisms on the site being treated. Foliar applications cannot be made to blooming plants and have greater potential to drift off target. Foliar applications of systemic insecticides also have a greater risk of killing beneficial organisms, which can lead to unintended pest flare-ups.

N = nontoxic; S = slightly toxic; M = moderately toxic; H = highly toxic; — = data not available.
This table is based on the experiments we have done to date and should not be considered final or complete.

Potential Nontarget Effects of Insecticides

Water Contamination

Every precaution should be taken to protect surface water and groundwater from pesticide contamination. Trunk injections pose the smallest risk to contaminating water because the insecticide is placed directly into the tree. Soil drench applications should only occur directly adjacent to the trunk of the tree, as directed on the label. Soil drenches should not be applied to sandy soils, where the water table is shallow, or near open water sources (ponds, lakes, streams). Soil injections should be made in accordance with the insecticide label and the equipment manufacturer’s instructions. Both dinotefuran and imidacloprid and their breakdown degradants can persist in groundwater for extended periods. When exposed to sun, both of these compounds break down readily, but their degradants may persist for much longer.

Pollinators and Other Insects

Some trees on which SLF has been observed feeding in high densities are also pollinated by bees (e.g., maples). Additionally, many native insects (caterpillars, beetles, lady beetles, lace-wings, parasitoid wasps, etc.) utilize these trees. Trees treated with systemic insecticides could have insecticide residue in their flowers and nectar the following spring. The effects of sublethal doses on non-target insects are not completely understood. Neonicotinoid insecticides, in particular, have been associated with bee health decline. Pyrethroids can be damaging to beneficial insects and could cause populations of secondary pests, such as mites and scale, to flare up. Generally, systemic insecticides are considered to have a reduced impact on natural enemies compared to broad-spectrum foliar-applied insecticides. The effect of SLF treatments on pollinators and other beneficial insects is currently under investigation.

Ongoing Research

Research is ongoing to understand the biology and behavior of SLF and to find better SLF management strategies. Research on the impact on tree health is focused on the physiological response of the tree to SLF feeding, which will involve the study of sap flow and the nutritional status of the plant over time. We are also evaluating whether SLF has a required plant host, and developing a ranked list of the preferred hosts.

Better management strategies may be developed by determining economic injury levels on various hosts, searching for useful biological control options (native and introduced predators, parasitoids, and fungal pathogens), evaluating pesticide efficacy and nontarget effects.

Summary

1. Spotted lanternfly is currently considered primarily a nuisance pest in ornamental landscapes.
2. Death of ornamental and shade trees has not been directly linked to SLF to date. SLF is considered a plant stressor. High infestation levels may reduce photosynthetic activity and energy storage.
3. Always scout for spotted lanternfly first before deciding to make a treatment. Not every tree on any given property needs to be treated. Nymphs move frequently within a landscape, feeding on a large variety of plant hosts. Be aware that SLF populations may fluctuate from year to year; do not assume what happened last year will happen in the coming year.
4. The active ingredients, methods, timing, and other treatment suggestions presented here are guidelines. We are conducting research to refine these guidelines.
5. Always follow the label for any pesticide application you make.
6. Check for updated versions of this fact sheet and other news related to spotted lanternfly by visiting the Penn State Extension Spotted Lanternfly website.

Prepared by Heather Leach, Brian Walsh, Amy Korman, and Emelie Swackhamer.