The Spotted Lanternfly (SLF), Lycorma delicatula, is an invasive species that poses a significant threat to agricultural and ornamental plant life. This pest weakens trees by feeding directly on the phloem sap using specialized mouthparts. This feeding results in the excretion of sugary waste known as honeydew, which encourages the growth of black sooty mold on the tree and surrounding surfaces. While a single SLF is unlikely to harm a healthy tree, large populations cause stress, branch dieback, and reduced growth. Protecting valuable trees requires implementing timely management strategies throughout the year.
Immediate Physical and Mechanical Barriers
The most accessible physical control measure occurs during the dormant season (September through May) when the insects are in the egg stage. Female SLFs lay egg masses on tree trunks, branches, rocks, outdoor furniture, and other hard, vertical surfaces. These masses are initially covered with a gray coating that dries and may crack, exposing the eggs underneath.
To destroy the eggs, homeowners should use a stiff tool, such as a putty knife, to scrape the mass off the surface. Scraping the material directly onto the ground is insufficient, as the eggs may still hatch. The scraped material must be immediately placed into a container filled with rubbing alcohol, hand sanitizer, or soapy water. Submerge the eggs for 24 to 48 hours to ensure complete destruction before disposal.
An additional mechanical barrier involves using sticky bands wrapped around tree trunks to trap flightless nymph stages. Banding is effective in the spring and early summer (late April through June) when young nymphs are highly mobile. These traps capture the first three nymph stages, which are black with white spots, before they mature.
A concern with sticky bands is the potential for unintentionally trapping non-target species, including small birds and beneficial insects. To mitigate this risk, all sticky bands must be covered with a protective mesh, such as chicken wire or hardware cloth. Bands should be checked frequently and removed at the end of the season to prevent harm to wildlife.
Strategic Timing for Life Cycle Targeting
Effective management relies on aligning control methods with the SLF’s single annual life cycle. The insect progresses through four nymph stages, beginning with egg hatch in late April or May. The first three stages are small, black insects with white spots that feed on soft, new growth.
The fourth nymph stage appears around late June or early July and develops distinct red patches in addition to the black and white markings. Adults emerge around mid-July to August and remain active until killed by a hard freeze in the late fall. Physical methods, like egg scraping, are best during winter dormancy, while insecticides target the nymph stages.
The SLF exhibits a strong preference for the non-native Tree of Heaven, Ailanthus altissima, which acts as a highly attractive feeding and reproductive host. Managing this invasive tree is a significant part of SLF control. Identifying and removing Ailanthus on a property is recommended to reduce population density.
A highly effective strategy involves using remaining Ailanthus trees as “trap trees.” Homeowners should remove approximately 90% of the Ailanthus, leaving a few male trees that do not produce seeds. These designated trap trees are treated with a systemic insecticide, drawing the SLF to feed on the treated sap and perish before migrating to valued trees. This selective approach concentrates the infestation and minimizes widespread chemical use.
Chemical Treatment Options and Safety Guidelines
Contact Treatments
Chemical control options are categorized into contact and systemic insecticides. Contact insecticides, such as those containing pyrethrins, bifenthrin, or carbaryl, kill the insect upon direct application. These products are best used as spot treatments for visible clusters of nymphs or adults on accessible parts of the tree trunk or foliage.
The main limitation of contact treatments is their short residual activity, offering little protection once the spray has dried. Organic options like insecticidal soap or neem oil require thorough coverage of the insect’s body and repeated applications. Less-toxic options require direct contact with the insect to be effective.
Systemic Treatments
Systemic insecticides provide longer-term defense by circulating the chemical throughout the tree’s vascular system. The insect is killed when it feeds on the treated sap, offering protection for weeks or months. Common active ingredients in systemic treatments include neonicotinoids like imidacloprid and dinotefuran.
Timing is crucial for systemic products, which must be applied early enough for the tree to absorb and distribute the chemical before the peak feeding period. Dinotefuran moves quickly through the tree, often providing faster control than imidacloprid, which can take several weeks to reach effective concentrations. Systemic treatments must be avoided during the tree’s flowering period to protect pollinators.
Application Methods and Safety
Systemic products can be applied as a soil drench, where the chemical is poured around the base of the tree and absorbed by the roots. While simple for homeowners, this method carries a risk of chemical runoff and exposure to nearby flowering plants. Trunk injections, where a concentrated product is injected directly into the tree’s xylem, are often preferred by professionals.
Trunk injection minimizes environmental exposure and is the most precise application method for large, mature trees. For large-scale treatment or the use of restricted-use products, consulting a certified arborist is advisable. The product label must be read and followed precisely to ensure safety and effectiveness, including wearing appropriate personal protective equipment (PPE) and adhering to local regulations.
Monitoring, Recovery, and Community Reporting
After implementing control measures, support the tree’s health to help it recover from the stress of sap loss. Simple cultural practices, such as providing adequate water during dry periods and maintaining mulch around the base, aid recovery. Continuous monitoring should be maintained throughout the year to check for reinfestation.
Monitoring efforts should focus on checking for new egg masses during the fall and winter months. This preventative action is the most efficient way to reduce the population for the following spring. Community involvement is key to controlling the spread of this invasive species.
If an infestation is discovered outside of an established quarantine zone, reporting the sighting to the state department of agriculture or local extension office is mandatory. This action is fundamental for tracking the pest’s expansion and allowing authorities to implement rapid, localized control measures.