The Spotted Lanternfly (Lycorma delicatula) is an invasive planthopper native to Asia, first discovered in Pennsylvania in 2014. Since then, it has spread across numerous states, threatening agricultural crops and ornamental plants. This pest feeds on the sap of over 100 plant species, including trees, shrubs, and vines. Understanding the mechanics of its feeding and the vulnerability of its host plants is necessary to determine if this insect causes tree death.
The Mechanism of Tree Damage
The damage caused by the Spotted Lanternfly (SLF) involves its specialized, piercing-sucking mouthparts, which tap directly into the plant’s vascular system. The insect extracts large quantities of phloem sap, the sugary fluid that transports nutrients created by photosynthesis. This constant sap extraction from the trunk, branches, and leaves depletes the plant’s stored energy and water, weakening the host over time.
As the insect ingests excess sap, it excretes a sticky, sugary substance called honeydew. This honeydew drips onto the plant and surrounding surfaces, creating a medium for black sooty mold growth. While the mold is not directly harmful to tree tissue, it coats leaves and stems, reducing the sunlight reaching the surface. This blockage diminishes the plant’s ability to perform photosynthesis, compounding the stress from sap loss.
Which Trees and Plants are Most Vulnerable?
The Spotted Lanternfly is a polyphagous feeder, meaning it consumes a wide variety of plants, but it prefers certain hosts. Its most significant host is the invasive Tree of Heaven (Ailanthus altissima), which is essential for the insect’s development and where it aggregates in large numbers. SLF survival rates are better, and females produce more eggs when feeding on Tree of Heaven compared to other species.
The SLF also targets plants of high economic value, such as grapevines, hops, and stone fruit trees (peaches, plums, and cherries). Grapevines are particularly susceptible to severe damage and yield reduction. The pest infests many common native and ornamental shade trees, including maple, willow, river birch, and black walnut, due to their high sugar sap content.
Do Spotted Lanternflies Directly Kill Trees?
Direct mortality from SLF feeding alone is rare for mature, healthy hardwood trees. Research indicates that heavy, sustained feeding can reduce the growth of native trees like maple and birch, but these trees often recover once the insect population moves on. For well-established, healthy trees, the stress from sap loss and sooty mold is usually insufficient to cause death, especially since the insects frequently move between hosts.
Death is a more likely outcome for high-value agricultural crops and younger, stressed trees. Intense, repeated infestations have killed cultivated grapevines and young saplings, particularly black walnut and maple. Tree mortality typically occurs due to cumulative stress, where SLF feeding combines with factors like drought, disease, or pre-existing health issues. The resulting nutrient loss makes the tree susceptible to secondary pests or pathogens that deliver the final blow.
Recognizing Infestation and Immediate Steps
Identifying an SLF infestation requires recognizing the insect in its various life stages and noting signs of feeding activity. Adults are about one inch long, with light brown forewings spotted with black and bright red hindwings visible when they move. Nymphs are small and wingless; they are black with white spots in early stages, later developing striking red and black patches before maturing.
Signs of feeding include honeydew coating surfaces beneath the tree and the subsequent growth of black sooty mold. Homeowners may also observe “weeping” wounds on the trunk where sap oozes from feeding sites.
In the fall and winter, egg masses are present, appearing as a smear of gray, putty-like material that dries to resemble cracked mud. Immediate steps should focus on physical removal, such as crushing or scraping egg masses into a solution of hot, soapy water or alcohol. Any sighting outside of a known quarantined area should be reported to local agricultural departments to help track and prevent further spread.