The Spotted Lanternfly (SLF), Lycorma delicatula, is an invasive planthopper that poses a significant threat to agricultural crops and ornamental plants across the United States. First detected in Pennsylvania in 2014, this pest feeds on plant sap using piercing-sucking mouthparts, weakening hosts such as grapevines, fruit trees, and various hardwood species. High populations excrete honeydew, a sugary substance that fosters the growth of black sooty mold. This mold further stresses plants and creates a nuisance in public spaces. Due to the insect’s rapid spread and ability to damage multiple industries, chemical intervention is often a necessary component of a comprehensive management plan.
Non-Chemical and Physical Control Methods
Before resorting to insecticides, simple physical methods can help reduce local SLF populations, especially in residential areas. The most direct method is physically destroying the insects by hand-squishing or knocking them into a container filled with rubbing alcohol or soapy water. Since SLF cannot bite or sting, this remains a safe and effective way to manage small numbers of nymphs and adults.
Scraping and destroying egg masses is another important non-chemical activity that targets the pest’s life cycle from late August through May. The eggs are typically laid on trees, rocks, outdoor furniture, and other hard surfaces, protected by a mud-like covering. Scraping the masses into a sealed bag or container with hand sanitizer or alcohol ensures the eggs are killed.
Trapping methods can also be employed to capture nymphs and adults as they crawl up tree trunks to feed. Circle traps, which act as funnels, are a recommended method for catching the insects. Sticky bands wrapped around tree trunks can also capture large numbers of nymphs. If sticky bands are used, a barrier must be installed over the sticky surface to prevent the accidental capture of non-target species, such as birds, bats, and beneficial insects.
Contact Insecticides for Immediate Knockdown
Contact insecticides kill the Spotted Lanternfly upon direct exposure, providing quick, localized control, particularly against clusters of nymphs and adults. These sprays are most effective when thorough coverage of the target insect is achieved. Their activity is short-lived; they do not persist long in the environment, and repeated applications may be necessary as new insects move into the treated area.
Insecticidal soaps and horticultural oils are low-toxicity options that kill the insect by disrupting cell membranes or suffocating it. These products require the spray to physically contact the pest to be effective. While they offer a reduced risk to the environment, their efficacy can be variable, and the insects may take several days to die.
Neem oil, which contains the active ingredient azadirachtin, functions as a contact insecticide and has repellent properties. Its effectiveness is good, but like soaps and oils, it offers little residual activity. Natural pyrethrins, derived from chrysanthemum flowers, are fast-acting contact insecticides that provide rapid knockdown of the pest.
Synthetic pyrethroids, such as bifenthrin and zeta-cypermethrin, are highly effective contact sprays that offer a longer residual effect on treated surfaces. These products can kill SLF that move into the area after the spray has dried. However, they are non-selective and pose a greater risk to beneficial insects. Contact sprays are often the preferred method for controlling early-stage nymphs.
Systemic and Residual Treatments for Host Plants
Systemic insecticides offer a longer-term management solution by being absorbed and distributed throughout the plant’s vascular system. When the Spotted Lanternfly feeds on the sap of a treated host tree, it ingests a lethal dose of the insecticide. This method is typically reserved for high-value trees or those serving as “trap trees” in areas of high infestation.
The most common active ingredients used for systemic control belong to the neonicotinoid class, specifically Dinotefuran and Imidacloprid. Dinotefuran is highly soluble, allowing it to move quickly through the plant tissue after application, making it a good choice for later-season applications. Imidacloprid is less soluble and requires more time for uptake, often functioning best when applied earlier in the season, such as after flowering to July.
Systemic treatments can be applied as a soil drench around the tree base, a basal bark spray on the trunk, or by trunk injection, which requires specialized equipment. Properly applied systemic insecticides can provide control for several weeks to months. The choice of chemical and application method impacts the duration and speed of efficacy.
A significant trade-off with systemic insecticides is the potential risk to non-target insects, particularly pollinators. Residues of these chemicals can be translocated into the nectar and pollen of flowering host plants, such as red maple. Studies indicate that residues from treatments made the previous year can persist in the flowers the following spring, potentially harming solitary bees and other pollinators.
Safe Application and Protecting Non-Target Species
The safe and effective use of any insecticide requires strict adherence to the product label, which is approved by the Environmental Protection Agency (EPA). The label provides detailed instructions on mixing, application rates, personal protective equipment, and environmental precautions. Using any pesticide in a manner inconsistent with its labeling is a violation of federal law.
Applicators should confirm that the specific site they intend to treat, such as an ornamental tree or a grapevine, is listed on the product label. Timing of application is paramount for minimizing harm to beneficial insects. Insecticides should never be sprayed onto plants that are currently in bloom to protect foraging pollinators from direct contact.
For systemic treatments, especially those containing neonicotinoids, applications should be made post-bloom to reduce the contamination of floral resources. Careful calculation of the product amount based on the tree’s size is necessary to avoid over-application, which increases the concentration in plant tissues and the resulting risk to pollinators. Unused or expired chemicals must be stored securely and disposed of according to local regulations to prevent environmental contamination.