The spotted lanternfly (SLF), Lycorma delicatula (White) (Fig. 1), is a non-native planthopper that can feed on a wide range of trees in the USA. SLF is native to China, India, and Vietnam and was first detected in Pennsylvania in September 2014. Since its initial detection, SLF has been confirmed in 12 additional states: New Jersey, Virginia, Delaware, West Virginia, Maryland, Connecticut, New York, Ohio, Indiana, Massachusetts, Tennessee, and North Carolina (Fig. 2). SLF is NOT detected or established in Georgia (as of June 2024). The potential economic and environmental impact of SLF is alarming. In states where SLF is already established, the estimated value of grape and tree fruit industries is $915 million, and that for the ornamentals industry is $2.6 billion (Urban 2020). This not only threatens the livelihoods of many but also the biodiversity and beauty of our landscapes. This underscores the need for immediate action to prevent its spread. There is no evidence of SLF feeding directly on nursery stock, but notable indirect impacts can be found in ornamental nurseries. Nursery stocks should be free of all life SLF stages before sale in the SLF-established zones. This requires insecticidal treatment, which increases labor costs.
Damage
Being polyphagous and capable of laying egg masses on various substrates, the spotted lanternfly (SLF) can impact a broad range of industries. Adult SLF emerges in late summer and aggregates on host plants to feed. Using piercing-sucking mouthparts, SLF takes in plant nutrients. Adults mostly feed on the trunk, whereas nymphs feed on the actively growing shoots. The presence of many adults feeding on a single tree (referred to as a “hot” tree) could result in heavy loss of phloem. This weakens trees over time and causes indirect effects, such as increased susceptibility to drought, secondary pests, or pathogens. Adult feeding sometimes causes weeping bark as the sap oozes out of the trunk (Fig. 3A). Adult SLF ingests more sap than they need, which is excreted as a sugary substance called honeydew. They produce honeydew more than aphids or scales. In some cases, honeydew falls as light rain from the tree canopy of infested trees. In the fall, the activity of ants, bees, and wasps attracted to honeydew is observed. Sooty mold fungus grows on honeydew, which blackens tree trunks and any substrates beneath SLF (Fig. 3B). In some cases, the sugars in honeydew ferment with time, giving an unpleasant appearance (Fig. 3C). The sooty mold growth and fermentation not only reduces the aesthetic value of affected trees but also the general landscape where the affected trees are present. While trees rarely die from SLF attacks, the pest exerts heavy stress on trees. When other biotic (disease or other insect infestation) and abiotic (e.g., drought) stress are present, the damage to SLF-infested trees is compounded. Severe yield reduction is observed in grapes, and it can reduce the value of maple (silver and red) and black walnut in the landscapes.
https://currituck.ces.ncsu.edu/2021/11/spotted-lanternfly-4
Life cycle
In northern US states, there is only one generation per year. In the fall (September to October), mated females lay egg masses on smooth surfaces of trees and shrubs (Fig. 4). Typically, eggs are found on the tree host they feed in the summer and fall. If the tree or hosts are not readily present, they can lay eggs on any structures they find. These structures could be non-living structures, such as fences, brick walls of the building, vehicles, furniture on the patios, etc. Females coat egg masses with a white substance. As they dry up, egg masses appear as mud patches or lichen growing on substrate surfaces (Fig. 5). About 30-50 eggs are found in an egg mass. Eggs are seed-like, brown-colored, and laid vertically. A female can lay up to two egg masses in its lifetime. The eggs overwinter within the patch, and slowly, the patch withers away as it nears hatch in the following year’s spring (Fig. 6).
In northern states, eggs hatch in April and June, which may be a little sooner in the southern states. They undergo four nymphal stages before molting into adults. The first (⅛ inches long), second, and third instars are black with white spots (Fig. 7A). Their size increases as they molt to higher instars. Fourth instars (½ inches long) are red with black and white spots (Fig. 7B) and are often found along with adults. Fourth instars molt into adults around August in northern US states). An adult is 1 inch long and ½ inches wide (Fig.1). The forewing of adults is gray colored with black spots (Fig. 1). The legs are black colored. The head is black with a pair of short, orange-colored antennae. The forewing completely covers the hindwing (Fig. 1). The tip of the hindwing is black (Fig. 8). white and black bands are present towards the abdomen. The lower region of the hindwing is red-colored with black spots. The wingspan is about 2.2 inches when expanded (Fig. 8). The abdomen is yellow-colored with black stripes in the center. Adults are often found in “hot” trees in aggregation (Fig. 9). Some adjacent trees may have no adults.
Dispersal
The egg-laying behavior – with egg mass on any substrate, helps them to disperse quickly in the late fall and winter to new areas. The hitchhiked eggs on rail cars, trailer trucks, recreational vehicles, or campers find new habitats in the following year when they hatch (Fig. 10). They have successfully adapted to new hosts in new locations. Visual monitoring of egg masses on vehicles and materials originating from established areas is a good practice to delay their establishment in new places. When detected, the egg masses can be physically destroyed by stomping or other means.
Host plant range
Spotted lanternfly feeds on more than 103 tree species; however, not all hosts support the development of nymphs. In northern states, the tree of heaven (Ailanthus altissima; Fig. 11) is considered a key host species that helps them develop and reproduce profusely. Some tree hosts do not support reproduction or development as they fail to produce eggs or nymphs without completing adulthood. Feeding hosts besides tree of heaven include red maple (Acer rubrum), silver maple (Acer saccharinum), black walnut (Juglans nigra), butternut (Juglans cinerea), River birch (Betula nigra), Rose (Rosa spp.), Staghorn sumac (Rhus typhina), Weeping willow (Salix babylonica), Wild grape (Vitis spp.) and Wine grape (Vitis vinifera).
Maples and grapes, including muscadine grapes, are common in north and central Georgia and South Carolina. It is not sure how tree hosts in southern states play a role in the population dynamics of SLF. Maples are widely planted in urban areas, including parks and residential and commercial sites. Similarly, wild grapes (including muscadine grapes) are typical in wood undisturbed lots and regions.
Monitoring
SLF adults and nymphs can be monitored using circle traps, sticky traps, jar traps, etc. For the circle trap, a metal mesh funnel is attached to the tree trunk to direct SFL into the collection container or bag (Fig. 12A). Those SLF entering the collection container or bag are trapped inside or killed using an insecticide strip inside the container. A commercially purchased methyl salicylate lure can be used within the collection container or bag to attract the SLF. The sticky trap is deployed by wrapping sticky tape around the tree trunk (Fig. 12B). The metal guard or mesh is used to cover the sticky card to prevent birds and other vertebrates (Fig. 12C). Traps should be monitored at regular intervals (once in 7 or 14 days). For the circle trap, methyl salicylate lure is usually replaced at one-month intervals. These traps are effective when deployed on susceptible tree hosts, such as Tree-of-heaven. These traps provide information on the life stage (s) present at a given time and estimate population size. Egg masses can be monitored using a lampshade trap. Construction of the lampshade trap is described here: Lampshade Trap Construction for Spotted Lanternfly Egg Masses (PDF) (P. Lewis, USDA APHIS, Forest Pest Methods Laboratory, Buzzards, MA)
Management
SLF feeding rarely causes damage to trees. However, extensive populations can cause a nuisance with sooty mold developed on the honeydew produced by SLF. This can also reduce the aesthetic value of the affected trees. Thus, SLF infestation is managed using insecticides. Tree injection, bark sprays, or soil drenches are effective methods of delivery of systemic insecticides, such as neonicotinoids. The best time to apply imidacloprid is from May to July. If dinotefuran is used, the best timing is from July to September. Pyrethroids, such as beta-cyfluthrin, bifenthrin, and zeta-cypermethrin, and reduced-risk insecticides, such as neem oil, horticultural and dormant oils, and insecticidal soap, are effective on adults and nymphs. The residual activity of reduced-risk insecticides is very short compared to pyrethroids and neonicotinoids. Because insecticide exposure can affect pollinators and other nontarget organisms, insecticides should be cautiously used. Biological control agents, such as praying mantis or spiders, are found attacking the SLF, but predator activity is not high enough to suppress the SLF population. Beauveria bassiana strains are effective on SLF adults and nymphs.
References
Barringer, L., and C. M. Ciafré. 2020. Worldwide feeding host plants of spotted lanternfly, with significant additions from North America. Environ. Entomol. 49: 999–1011. https://doi.org/10.1093/ee/nvaa093
Clifton, E. H., L. A. Castrillo, A. Gryganskyi, and A. E. Hajek. 2019. A pair of native fungal pathogens drives the decline of a new invasive herbivore. PNAS 116:199178–80
Simisky, T., J. Piñero, E. Barnes, J. F. Orth, T. LaScola-Miner. 2022. Spotted Lanternfly Management. UMass Extension Landscape, Nursery, and Urban Forestry Program. https://ag.umass.edu/landscape/fact-sheets/spotted-lanternfly-management