The spotted lanternfly (Lycorma delicatula, SLF) is an invasive insect that feeds on many plant species, including economically significant agricultural and horticultural crops, ornamental nursery plants, and trees. Despite its name, SLF is not a fly – it is a planthopper that rarely uses its wings to fly, preferring to use its legs to hop. It is native to parts of Asia, including China, Vietnam, and Bangladesh, and was first discovered in North America in 2014 in Pennsylvania. It has since spread to and become established in twelve states, including Connecticut, Delaware, Indiana, Maryland, Massachusetts, New Jersey, New York, Ohio, Pennsylvania, Virginia, West Virginia, and most recently, North Carolina (Fig. 1).
SLF egg masses are flat and covered in a grayish, waxy, mud-like deposit for protection. They can be found on several surfaces, including plant material, rocks, vehicles, houses, trees, and almost anything else (Fig. 2a-b). SLF have an incomplete metamorphosis, meaning eggs hatch into nymphs, which look somewhat like adults. SLF nymphs are tiny, starting at about one-eighth inch long, and are black with white spots (Fig. 2c). They grow to about one-half inch long, or the size of a nickel, by their final nymphal stage (or instar), where their color changes to red with white dots and black stripes (Fig. 2d). Adult SLF are around one inch long and a half-inch wide with a black head and long black legs (Fig. 2e). The body is primarily black, but females have yellow bands on the underside of their abdomen. The forewings are a grayish color with black spots. The tips of the forewings are also black and gray and appear to have a striped pattern. Their hind wings are more colorful, with red, black, and white markings (Fig. 2f). SLF adults are the only life stage with wings, and while they can fly, they are weak fliers and prefer to use their legs to walk or hop. Thus, their wings are rarely open, which largely hides the colorful hindwings.
SLF has one generation per year in the Mid-Atlantic region of the United States. Egg masses containing 30 to 50 eggs are laid in the fall and hatch in the spring. After hatching, SLF goes through four instars over about eight weeks before becoming adults in mid-summer. Adult SLF feed during the summer and early fall and mate before laying their eggs in the fall.
SLF is a generalist herbivore that can feed on over 100 host species, including several agricultural crops and tree species important to South Carolina. Hosts include apples (Malus), plums and peaches (Prunus), grapes (Vitis), cucumbers (Cucumis), basil (Ocimum), blueberry (Vaccinium), black walnut (Juglans), maple (Acer), oak (Quercus), birch (Betula), willow (Salix), sycamore (Platanus), and many other woody deciduous species. Ornamental species, including roses (Rosa), forsythia (Forsythia), hibiscus (Hibiscus), and zelkova (Zelkova), can also be used as hosts. SLF typically does not use conifer species as hosts for feeding, but they may oviposit on some economically important conifer species (e.g., Christmas trees). The invasive tree of heaven (Ailanthus altissima) is SLF’s preferred host, and both nymphs and adults can be observed feeding on this species (https://blogs.clemson.edu/fnr/2021/10/12/invasive-species-spotlight-tree-of-heaven-ailanthus-altissima/).
Signs of Damage
Different SLF life stages often feed together (Fig. 3a), sometimes in extremely high populations (Fig. 3b). SLF is a sap feeder, and feeding damages the host by removing fluids from the plant. Typically, this feeding is mainly a plant stressor that weakens the plant, though high levels of feeding can cause plant death. Early signs of feeding may include plant wilting, while later feeding damage may appear as branch or plant dieback. SLF feeding causes the insects to produce copious amounts of liquid excrement called honeydew. Sap from the plant is high in sugar content – as is the honeydew – which often results in a sticky covering on anything below SLF feeding sites. Honeydew attracts many different kinds of insects, including ants, wasps, and bees. Eventually, a dark fungus called sooty mold grows on this honeydew (Fig. 3c). Sooty mold can reduce a plant’s ability to photosynthesize and can also stain objects on which it grows, including vehicles and tree trunks.
Economic and Ecological Importance
SLF has already had a significant impact on the agriculture and forest products industries. According to a study completed in 2020, Pennsylvania’s agriculture industry loses an estimated $43 million statewide annually, with worst-case scenario estimates of over $99 million per year. Its forestry industry loses an estimated $153 million statewide, with a worst-case scenario estimate of over $236 million per year due to the damages caused by SLF.
In non-agricultural areas, SLF can be a significant landscape and nuisance pest. It damages ornamental trees through its extensive feeding and the production of honeydew, which then attracts stinging insects and promotes the growth of sooty mold. SLF is estimated to have a $2.6 billion impact on the ornamental plant industry of affected states.
The estimated impact of SLF on the fruit tree and grape industry was $915 million as of 2019, and there are likely risks for peach orchards in South Carolina, one of the largest peach-producing states in the country. Peaches are in the same family as apples, a known host for SLF (Fig. 3b). South Carolina also is home to several vineyards that could be damaged, and native species such as muscadines are potentially at risk. SLF feeding can reduce fruit production and increase management costs. For instance, from 2016 to 2018, the average cost of insecticides used by Pennsylvania vineyards tripled. SLF-infested materials would also not be allowed to be shipped, further impacting South Carolina’s fruit production industry.
There are limited options for SLF management, partly because SLF are highly mobile, and infestations typically occur in large numbers. Broad-spectrum insecticides are effective and will kill SLF, though these will also result in the mortality of other beneficial arthropods. Many insecticides already used to control other pests can protect crops against SLF infestations, but always read and follow the label on the insecticide container – the label is the law! Around homes and businesses, SLF can be managed as a nuisance insect by physically removing the insects. Biological control options are also being researched to aid in the management of SLF. Native generalist predators (e.g., praying mantids, spiders, birds) will feed on SLF, and two fungal pathogens were recently discovered that kill SLF, though these are not currently recommended for management. Research continues to optimize current biocontrol possibilities and to find new potential biocontrol agents from SLF’s native range.
Since SLF frequently congregates in large numbers on host species, monitoring for infestations can be an effective way to detect populations. SLF commonly infest tree of heaven, and the male trees (which do not produce seeds) can be used as sentinel or trap trees. After removing female tree-of-heaven (females that produce seeds should be removed from surrounding areas to decrease the number of hosts near nurseries and agricultural areas), male trap trees can be left to attract SLF. These trees can then be treated with insecticides to kill the SLF. Sticky bands may be added to help monitoring efforts by trapping the nymphs crawling on the host tree, but there are currently no baits available for attracting SLF to traps.
Preventing the Spread
Since the management of SLF is complex and rarely successful at eradicating populations, preventing the spread plays a significant role in controlling this invasive pest. Quarantine zones are established in areas with active populations, and any equipment or vehicles should be checked for SLF life stages. Removing potential host plants (e.g., tree of heaven) from around agricultural areas or nurseries can be beneficial. If an insect is suspected to be SLF, capture the insect or take a picture and report it to your local Clemson Extension agent or to Clemson DPI using the online reporting tool.
- Don’t move firewood: https://www.dontmovefirewood.org/
- LGP paper: Spotted Lanternfly Management in Nurseries, Orchards, Vineyards, and Natural Areas in South Carolina and Georgia | Land-Grant Press (clemson.edu)
- APHIS website: USDA APHIS | Spotted Lanternfly
- Penn State Extension: Spotted Lanternfly Management Guide (psu.edu)
- Penn State Extension Impacts: https://extension.psu.edu/scientists-examine-potential-economic-impact-of-spotted-lanternfly-in-pennsylvania
- NYS IPM website: https://nysipm.cornell.edu/environment/invasive-species-exotic-pests/spotted-lanternfly/