By now, most arborists have heard of spotted lanternfly (SLF), yet another pest from Asia recently arrived to our country that is creating economic and environmental problems in the eastern United States.
First detected in Berks County, Pennsylvania, in 2014, SLF is not a fl y at all. Spotted lanternfly belongs to a group of insects known as fulgorids, part of a large clan of insects called the Hemiptera, many of which are sap-feeding plant pests including aphids, soft scales, mealybugs, whiteflies, plant bugs, stink bugs and others. The common name, lanternfly, was first given to fulgorids with the mistaken belief that a hallmark enlarged structure on their heads was luminescent.
Like the aforementioned plant pests, lanternflies pierce plants with soda strawlike mouthparts, tap into vascular tissue and remove sap. Immature stages, called nymphs, and adults feed on phloem. Densities of lanternflies on individual plants can be staggering. Hundreds and even thousands have been observed on a single tree. By virtue of their high population densities, large amounts of phloem are removed from the tree or shrub.
There are several downsides to all this sucking and sap removal. The sugary waste product of their feeding, called honeydew, often is excreted in prodigious amounts. As with honeydew produced by soft scales and aphids, lanternfly honeydew fouls foliage and fruit, making leaves sticky and fruit unmarketable. This presents a serious economic problem for growers of apples, cherries, peaches and especially grapes, one of their favorite hosts.
Honeydew is also a substrate for sooty mold fungus, which further disfigures leaves and fruit. Honeydew’s high sugar content and the fermentation products associated with honeydew attract a variety of stinging insects such as yellow jackets, bees, and wasps, creating an additional concern for folks, especially those with allergies to stinging insects. Plant sap may continue to weep from wounds where lanternflies have fed.
More than 70 species of ornamental trees, fruit-bearing trees, and vines, including grapes, serve as hosts for SLF. In addition to the aforementioned fruit crops, SLF has been reported on more than 70 species of host plants. According to a recent publication by Siminsky (2019), the list of highly valued and common street and shade trees used by SLF includes “American beech (Fagus grandifolia), American linden (Tilia americana), American sycamore (Platanus occidentalis), big-toothed aspen (Populus grandidentata), black birch (Betula lenta), black cherry (Prunus serotina), black gum (Nyssa sylvatica), black walnut (Juglans nigra), dogwood (Cornus spp.), Japanese snowbell (Styrax japonicus), maple (Acer spp.), oak (Quercus spp.), paper birch (Betula papyrifera), pignut hickory (Carya glabra), sassafras (Sassafras albidum), serviceberry (Amelanchier canadensis), slippery elm (Ulmus rubra), tulip poplar (Liriodendron tulipifera), white ash (Fraxinus americana) and willow (Salix spp.).”
The direct damage to plants caused by vast numbers of probing mouthparts remains a largely unanswered question. However, in their native range, dense populations of lanternflies have been reported to cause wilting and dieback of branches. Here in the U.S., infestations of lanternfly have not been observed to kill ornamental or shade trees to date (Leach et al. 2019). The final insult created by SLF is a significant “yuck” factor when hundreds of large, colorful insects aggregate on trees, shrubs and vines to feed, or accumulate on sidewalks and lawns beneath trees that have been treated with insecticides to die.
Dara et al. (2015) provided a detailed account on the biology and ecology of SLF. In their native range, SLF has a single generation, which is also the case in the invaded regions of the United States. Eggs of SLF are the overwintering stage. Eggs, deposited in late summer and through autumn in batches of 30 to 50, are masked with a gray, waxy, mud-like cover and measure roughly one inch in length. As egg masses age, the color changes from gray to brown. Beneath these covers, small seed-like eggs are found in four to seven parallel rows.
Egg masses are deposited on trunks and branches of trees and shrubs that serve as hosts for nymphs and also on non-plant substrates, including dead plant material, lawn furniture, stones, masonry products, landscaping materials, vehicles and landscaping equipment. This biological quirk allows us to easily understand how this bug might have arrived undetected with a shipment of goods from a foreign land and how it is easily, and unwittingly, transported from location to location.
As temperatures warm in spring, eggs hatch and tiny nymphs begin to suck plant sap. Nymphs pass through four stages as they feed and develop throughout the spring and summer. Egg-laying adults appear in mid-summer and linger into late autumn.
Nymphs sport black background colors when young and later turn red. These background colors are speckled with white spots. Moth-like adu lts have brownish forewings bespectacled with dark spots, and their amazing hindwings have patches of red, white and black with dark spots. The bright colors of the adult are thought to startle predators when displayed and warn them of the noxious nature of the insect. Birds have been reported to vomit after dining on spotted lanternflies.
SLF on the move
Following the initial detection of SLF in Berks County, Pa., in 2014, this rascal has been on the move, first slowly but recently with increasing speed. By 2015, the quarantine zone in Pennsylvania had expanded into neighboring Montgomery County. In 2016 and 2017, it marched eastward into Lehigh, Bucks and Northampton counties, where quarantines were put in place. By 2018, Monroe, Carbon, Schuylkill, Lebanon, Lancaster, Chester, Philadelphia and Delaware counties joined the crowd, and by June of 2019, Dauphin County was added to the list.
Pennsylvania is not alone in its SLF woes. New Castle County, Delaware, reported its first living SLF adult in November In January 2018, an infestation was confirmed in Frederick County, Virginia, near Winchester. Mercer, Hunterdon and Warren counties in New Jersey joined the quarantine club in 2018 when lanternflies crossed the mighty Delaware River from Pennsylvania and entered the Garden State. By late summer of 2019, government agencies initiated programs to suppress populations of lanternflies in Cecil and Harford counties in northeastern Maryland.
Like other recent exotic invaders such as the brown marmorated stink bug, SLF is an excellent hitchhiker and stowaway. The proximity to several major interstate highways passing through eastern Pennsylvania has probably accelerated the dispersal of SLF and will continue to do so. In addition to quarantines triggered by known infestations of SLF, as of June 2019, individual egg masses and adults both dead and alive have been discovered in 11 additional counties in Pennsylvania, five additional counties in New Jersey, 11 counties in New York and one county each in Connecticut, Delaware and Massachusett’s (NY State IPM 2019).
The initial entry of SLF to the U.S. is thought to have taken place as an egg mass attached to a shipment of stones from Asia. Since adult SLF deposit eggs on a wide variety of substrates beyond trees, shrubs and vines, the Pennsylvania quarantine restricts the movement of “any living stage of the spotted lanternfly, Lycorma delicatula, including egg masses, nymphs, and adults; brush, debris, bark, or yard waste; landscaping, remodeling or construction waste; logs, stumps, or any tree parts; firewood of any species; grapevines for decorative purposes or as nursery stock; nursery stock; crated materials; and outdoor household articles including recreational vehicles, lawn tractors and mowers, mower decks, grills, grill and furniture covers, tarps, mobile homes, tile, stone, deck boards, mobile fire pits, any associated equipment and trucks or vehicles not stored indoors.”
Biotic resistance – Mother Nature pushes back
Biotic resistance refers to the ability of living things in one place to limit or prevent the establishment of invasive organisms from another place. Biotic resistance is thought to be one reason why more exotic species that land on our shores fail to establish and spread. In the case of SLF, we see evidence of some of our indigenous natural enemies pushing back on invading SLF.
Early reports of native predators killing SLF came in 2015 when the awesome predatory assassin bug, Arilus cristatus, Circle #47 on RS Card or visit https://tcia.org/rsc was discovered dining on a male lanternfly in Berks County, Pa. (Barringer and Smyers 2016). This voracious generalist predator, also known as the wheel bug, is known to feed on many invasive pests, including gypsy moths, Japanese beetles and brown marmorated stink bugs. A second predatory bug, Apoecilus cynicus, also was observed killing a female lanternfly. Due to the seasonal overlap with lanternfly and habitat preferences of these predators, the authors were optimistic that these bugs could play a role as biological control agents for SLF (Barringer and Smyers 2016).
In 2016, a tiny parasitic wasp, Ooencyrtus kuvanae, that often attacks and kills eggs of the dastardly gypsy moth, was discovered parasitizing eggs of SLF under natural field conditions in Pennsylvania (Liu and Mottern 2016). This wasp may also help stem outbreaks of SLF.
In autumn of 2018, a forested area near an apple orchard was the scene of a massive die-off of SLF. Clever molecular analyses of SLF cadavers revealed that two fungi teamed up to put a beat-down on this high-density population of pests. The microbial agents were Batkoa major and Beauveria bassiana. The former fungus was more commonly associated with SLF in trees, while the latter was more commonly found infecting SLF on the ground. Although it is unknown whether or not these or other pathogens will drive boombust cycles of SLF, the authors expressed hope that fungal inoculum remaining in the environment might help suppress future
local outbreaks of SLF (Clifton et al. 2019). Other observational accounts have listed praying mantises, spiders and lacewings attacking and killing various stages of SLF (Penn State Extension – https://extension.psu.edu/spotted-lanternfly, Kuhn and Martinson personal communication).
IPM for spotted lanternfly
Current management strategies rely on an integrated approach for reducing populations of SLF in landscapes. As with all integrated pest management (IPM) programs, the first step is to correctly identify the causal agent. In the case of SLF, this is an easy one, as no other large sucking insect pest approximates the appearance and plant injury caused by SLF. Images, life-cycle charts and timing of intervention tactics for SLF can be found at Penn State’s remarkable spotted lanternfly website, posted by Leach et al. (2019) (https://extension.psu.edu/spottedlanternfly-management-for-landscapeprofessionals).
Cultural and mechanical tactics
Although SLF is known to use more than 70 plant species as hosts, it does have key plants for feeding and egg laying. Tree of heaven, Alanthus altissima, is one such key plant. If clients have tree of heaven on their properties, a plan for removing them should be discussed. Leach et al. (2019) also recommend removing other favored hosts such as wild grapes and oriental bittersweet, where populations of SLF may build. Branches of trees infested with SLF that overhang patios and decks also may be pruned to reduce honeydew and displaced SLF from landing on tables, guests, food and libations.
Physical removal of egg masses by scraping them from trees and other substrates in the landscape also may help reduce SLF on individual properties. Egg masses should be scraped into containers that can be sealed and destroyed or put into containers containing soapy water and later discarded.
Another mechanical tactic suggested for reducing populations of SLF is the placement of sticky barrier bands on boles of infested trees. Eggs deposited on non-host substrates, such as lawn furniture and rocks, produce nymphs that must find a food source to develop. Barrier bands placed on trees prior to the time of egg hatch may intercept nymphs as they attempt to ascend trees to feed. Bands left in place from May until October may trap nymphs and adults throughout the period that they feed (Dara 2015, Lynch et al. 2019).
Fortunately, several active ingredients and methods for delivering them have proven highly effective in killing various life stages of SLF. Some of the earliest studies of insecticides conducted in Asia found pyrethroids, organophosphates and neonicotinoids lethal to SLF (Dara et al. 2015). Other studies in Asia revealed pyrethrum and neem extracts capable of causing death in 95% or more of SLF adults treated with these insecticides. Here in the United States, SLF are major pests of stone fruit. Insecticidal trials on peaches by Biddinger and Leach (2019) found several active ingredients available to arborists to be highly effective in killing SLF nymphs. Spray residues of bifenthrin, cypermethrin, carbaryl, acephate and dinotefuron provided 100% mortality on the initial day of exposure, and, in the cases of bifenthrin and carbaryl, this level of mortality lasted one week.
Other active ingredients available for arborists and the ingredients’ associated levels of mortality at the first day of exposure (enclosed in parentheses) were as follows: indoxicarb (98%), acetamiprid (89.5%) and spinosad (57.9%). In compiling a list of products to be used by landscape professionals, Leach et al. (2019) provided the following:
The systemic dinotefuron provided excellent levels of control of adult SLF when applied to the soil, injected into the trunk or as trunk sprays with excellent levels of residual activity. Imidacloprid provided excellent control with excellent residual when injected, but variable levels of control and residual activity when applied as a soil drench. Contact insecticides applied as sprays that provided excellent levels of control against nymphs and adults included bifenthrin, cypermethrin, carbaryl, malathion, tau fluvalinate – tebuconazole and natural pyrethrins. However, of these, only bifenthrin and carbaryl provided excellent and good levels of control after two and one weeks, respectively. Other compounds, some of which can be purchased with OMRI labels, and their levels of control (shown parenthetically) include neem oil (good), insecticidal soap (good) and horticultural oil (good). However, all of these showed poor residual activity. Horticultural oil also has been shown to provide mortality of 71% when applied to egg masses at a rate of 3%.
Additional details on non-target effects, timing and application methods are found in very useful detail in the publication by Leach et al. (2019) that can be accessed at this link: https://extension.psu.edu/spotted-lanternfly management-forlandscape-professionals.
As with all pesticide applications, always follow directions on the label, use personal protective gear as directed, be aware of environmental warnings – particularly those related to pollinators and aquatic organisms, and adhere to regulations of state and local jurisdictions regarding pesticide use.
What’s next for SLF?
In the absence of an unforeseen miracle, chances are good for the continued spread of SLF, particularly in the eastern U.S. due to growing populations of this pest, its proclivity to deposit eggs on plants and non-plant substrates and a system of major interstate highways that transect the generally infested region. We can hope that indigenous natural enemies continue to find SLF a suitable source of food and that their impact will help reduce populations in the future. Agencies within USDA have already identified several biological control agents of SLF from abroad that may, upon vetting and approval, be released to help stem threats posed by SLF.
An integrated approach of host-plant reduction, mechanical destruction of life stages and a diverse array of highly efficacious active ingredients and application methods can be combined to protect our valued trees, shrubs and crops from insults caused by this beautiful but noxious exotic pest.
Surendra K. Dara, Lawrence Barringer, and Steven P. Arthurs. 2015. Lycorma delicatula (Hemiptera: Fulgoridae): A New Invasive Pest in the United States. Journal of Integrated Pest Management, Volume 6, Issue 1. https://doi.org/10.1093/jipm/pmv021
Lawrence E. Barringer and Erica Smyers. 2016. Predation of the Spotted
Lanternfl y, Lycorma delicatula (White) (Hemiptera: Fulgoridae) by Two Native Hemiptera. Entomological News 126(1):71-73
Lawrence E. Barringer and Heather L. Leach. 2019. Updated Insecticide Recommendations for Spotted Lanternfly on Grape. https://extension.psu.edu/updatedinsecticide-
Eric H. Clifton, Louela A. Castrillo, Andrii Gryganskyi and Ann E. Hajek. 2019. A pair of native fungal pathogens drives decline of a new invasive herbivore. Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1903579116
Heather L. Leach, Emelie Swackhamer and Amy Korman. 2019. Spotted Lanternfly Management for Landscape Professionals. https://extension.psu.edu/spotted-lanternfly – m a n a g e m e n t – f o r – l a n d s c a p e -professionals
Houping Liu and Jason Mottern. 2017. An Old Remedy for a New Problem?
Identifi cation of Ooencyrtus kuvanae (Hymenoptera: Encyrtidae), an Egg Parasitoid of Lycorma delicatula (Hemiptera: Fulgoridae) in North America. Journal of Insect Science. 17(1): 18
NY State IPM. 2019. Spotted lanternfly. https://nysipm.cornell.edu/environment/invasive-species-exotic-pests/spottedlanternfly/
Tawny Siminsky. 2019. Spotted Lanternfly. University of Massachusetts. https://ag.umass.edu/landscape/fact-sheets/spotted-lanternfly
Michael J. Raupp, aka The Bug Guy, is a professor and extension specialist at the University of Maryland, in College Park, Md. A fellow of the Entomological Society of America, he speaks extensively in this country and abroad, has published numerous articles, chapters and books and frequently appears on television and radio. His most recent book, 26 Things That Bug Me, published by ISA, introduces youngsters to the wonders of insects; and Managing Insects and Mites of Woody Plants: An IPM Approach, is a standard for arborists in its third printing and available through TCIA. His research and outreach are supported through grants from the ISA’s Tree Fund, USDA – SCRI and USDA – McIntire-Stennis Programs.
This article was based on his presentation on the same subject at TCI EXPO
2018 in Charlotte, North Carolina. To listen to an audio recording of that presentation, go to this page in the digital version of this issue of TCI Magazine online, under the Publications tab at www.tcia.org, and click here.