The Spotted Lanternfly (Lycorma delicatula) is an invasive planthopper that threatens agricultural and forestry industries across the United States. Native to parts of Asia, including China, India, and Vietnam, its populations there are typically kept in check by natural predators and pathogens. The species was first confirmed in North America in 2014 in Berks County, Pennsylvania. The lanternfly is a highly mobile hitchhiker that spreads primarily by laying egg masses on vehicles, outdoor furniture, and other portable items, allowing it to rapidly expand its range beyond its limited natural flying ability.
Mechanism of Direct Plant Damage
The primary harm the spotted lanternfly inflicts on plants comes from its specialized feeding behavior. The insect uses piercing-sucking mouthparts to tap directly into the plant’s vascular system, specifically the phloem tissue. Phloem is the living tissue responsible for transporting sugars, amino acids, and other vital nutrients produced during photosynthesis throughout the plant. By continuously drawing out this sugary sap, the lanternfly essentially depletes the host plant’s energy reserves and stored starches.
Heavy feeding pressure from large populations of lanternflies, particularly the late-stage nymphs and adults, can significantly stress the host, resulting in stunted growth, wilting, and reduced ability to withstand other environmental factors. The piercing of the bark and stems also creates small wounds that often ooze fermented sap, which attracts other insects and can serve as an entry point for plant pathogens. In susceptible hosts like grapevines and young saplings, this prolonged feeding can lead to dieback of branches, loss of winter hardiness, and even complete plant death.
The lanternfly is a generalist feeder, documented on over 70 plant species, though it focuses its feeding on key targets. While early-stage nymphs feed on a variety of plants, the adults tend to concentrate on trees like the invasive Tree of Heaven (Ailanthus altissima), black walnut, maples, and, most notably, grapevines. Sustained, high-density feeding on these preferred hosts drastically reduces carbon and nitrogen storage and inhibits gas exchange in the leaves.
The Secondary Harm of Honeydew and Sooty Mold
The indirect damage caused by the spotted lanternfly stems from a sticky, sugary excretion called “honeydew.” Because the insect feeds on vast quantities of phloem sap to extract necessary nutrients, it excretes the excess sugar-water as a sticky waste product. This honeydew coats the host plant’s leaves, stems, and surrounding surfaces, creating a glossy film.
This sugary residue acts as an ideal growth medium for sooty mold. Sooty mold grows on the honeydew coating, forming a thick, black layer that covers the leaves. This layer significantly reduces the amount of sunlight reaching the plant’s surface, decreasing the plant’s ability to photosynthesize. This blockage further compounds the stress already caused by the lanternfly’s sap depletion.
The accumulation of honeydew and sooty mold stains outdoor surfaces, including decks, cars, patio furniture, and equipment underneath infested trees, making them difficult to clean. Furthermore, the honeydew attracts other nuisance insects, such as wasps, bees, and ants, complicating outdoor activities and crop harvests. This secondary harm can make ornamental plants and public spaces unmarketable or unusable, even if the plant itself does not die.
Economic Toll on Agriculture and Timber
Viticulture, or grape growing, faces the greatest risk, as high-density lanternfly feeding can cause rapid vine decline. This leads to loss of the current year’s crop and affects the vine’s ability to produce fruit in subsequent seasons. The sooty mold growing on honeydew also contaminates berries, making the fruit unmarketable even if the vines survive the feeding.
Estimates suggest the overall annual economic impact on a single state like Pennsylvania could reach hundreds of millions of dollars if the pest is not contained. Direct agricultural losses in Pennsylvania could be around $42.6 million, with the nursery, fruit grower, and Christmas tree sectors absorbing the largest financial hits. For the forestry sector, the annual impact of lanternfly feeding on trees like soft maple, oak, and black walnut was estimated to be over $152 million.
Beyond direct crop and timber loss, the presence of the invasive species forces significant management and regulatory costs. Quarantines are established to prevent the movement of the pest, which imposes restrictions on the transport of goods, vehicles, and materials from infested areas to uninfested ones. Businesses must implement costly inspection and treatment protocols for equipment and products leaving the quarantine zones, adding substantial overhead. These costs include pesticide applications, the removal of heavily infested host trees, and extensive public outreach efforts needed to slow the spread of this hitchhiking pest.