Last November we visited the spotted lanternfly revealed at a truck stop along Route 78 in southeastern Pennsylvania. With the discovery of the lanternfly in Northern Virginia in January of 2018 and the recent press coverage surrounding this announcement, it is time to learn a bit more about the next big invader from China. In what has become a never ending stream of invasive species arriving in the US, the lanternfly was first detected in Berks County, PA, in 2014. How spotted lanternfly arrived in the US is not clear, but like many recent invaders this one is an excellent stowaway and likely arrived on a shipment of goods from Asia. In addition to its native China, the spotted lanternfly is invasive in Korea, Taiwan, and Vietnam. Since its discovery in Pennsylvania, it has been detected in Delaware in 2017 and Northern Virginia and New York in the winter of 2018. First discovered in one small area of Berks County in 2014, it has spread throughout much of Southeastern Pennsylvania and now the following counties are under quarantine for this pest: Berks, Bucks, Chester, Lehigh, Montgomery, Northampton, Monroe, Carbon, Schuylkill, Lebanon, Lancaster, Delaware, and Philadelphia.
Spotted lanternfly is not a fly at all. It belongs to a group of insects known as fulgorids, part of a large clan of insects called the Hemiptera, a clan that includes other sap-feeding plant pests including aphids, soft scales, mealybugs, and whiteflies. Like the aforementioned rogues, lanternflies pierce plants with soda-straw-like mouthparts, tap into vascular tissue, and remove sap. In the case of the spotted lanternfly, nutrient rich phloem is their target. Both adults and the youngsters, called nymphs, remove large quantities of phloem sap from the tree as they feed. The excess is excreted from their rear end as a sugary waste product called honeydew and herein lies the problem. More than seventy species of ornamental trees, fruit bearing trees, and vines including grapes serve as hosts for spotted lanternflies. Hundreds of these rascals have been observed feeding on a single plant where they rain copious amounts of honeydew on vegetation and the earth below. As with honeydew from soft scales and aphids, the honeydew excreted by lanternflies fouls foliage and fruit, making leaves sticky and fruit unmarketable and thus presenting a huge economic problem for growers of apples, cherries, peaches, and grapes, some of their favorite hosts. As with other phloem feeders, honeydew serves as a substrate for the growth of fungus known as sooty mold which further disfigures leaves and fruit. Sweet honeydew and its fermentation products also attract a variety of stinging insects like yellow jackets and other wasps. In addition to excreting honeydew, lanternflies have been reported as so numerous on some plants that they cause wilting and dieback of branches.
On a rainy November day at the edge of a truck stop on an interstate highway in Central Pennsylvania spotted lanternflies lining the trunk of a Tree of Heaven suck sap and try to evade the inquiring lens of a bug geek’s camera.
One plant that seems especially important to their biology is Tree of Heaven, Ailanthus altissima, an invasive and urban colonist made famous by Betty Smith as the “Tree that Grows in Brooklyn.” Tree of Heaven is a widely distributed colonist of disturbed habitats and a favored host for spotted lanternfly egg laying. Adults and nymphs sucking the sap of Tree of Heaven are thought to imbibe toxic alkaloids, thereby making themselves toxic. This is problematic when lanternflies infest grapes and may taint grapes grown in vineyards for wine. Their proclivity to feed on toxin-laden plants has been exploited in Eastern cultures for medicinal purposes. Unfortunately, there are no reports of lanternflies limiting the spread of invasive Tree of Heaven but their fondness for Alianthis makes Tree of Heaven an excellent sentinel plant, one that should be inspected to detect incipient infestations of the lanternfly.
The spotted lanternfly has a single generation in its native range and also in the United States. Winter is spent as eggs. The female lanternfly deposits eggs in rather nondescript batches of 30–50 cloaked with a waxy mud-like cover roughly one inch long that turns brown or gray with age. Beneath the cover, the eggs are seed-like and deposited in 4-7 parallel rows per mass. These egg masses are often laid on tree trunks but have also been discovered on substrates such as stones, vehicles, and lawn furniture. It is easy to see how this bug might have arrived undetected with a shipment of goods from a foreign land. In spring as temperatures warm eggs hatch and tiny nymphs begin to suck plant sap. Four nymphal stages feed throughout the spring and summer and adults appear in mid-summer and linger into autumn when eggs are laid. Nymphs have black and later red bodies speckled with white spots. Adults are moth-like with brownish forewings bespectacled with dark spots, and dazzling hindwings sporting red, black, and white with dark spots. The bright colors of the adult are thought to warm predators of the noxious nature of the insect.
What has been done to stop the spread of this pest? To date more than 1.5 million spotted lanternflies have been killed by volunteers in Berks and surrounding counties. At present, a quarantine to stop its spread to new areas and slow its spread within the quarantined area has been placed around municipalities in thirteen Southeastern counties. This quarantine restricts the movement of “Any living stage of the Spotted Lanternfly, Lycorma delicatula. This includes 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; 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.” Delimiting surveys were conducted to determine the spread of the bug and attempts are underway to destroy the pest where it is found.
Other control measures include scraping egg masses from trees and putting sticky barrier bands around the trunks of trees to prevent lanternflies from reaching the canopy. Brown sticky bands appear to be more effective in trapping nymphs than those of other colors. Several insecticides labeled for use on ornamental trees and shrubs have proven effective in killing lanternfly nymphs and adults. Many of these compounds are on EPAs reduced risk list and others listed by the Organic Materials Review Institute (OMRI). These should be used whenever possible to minimize risk to the environment and non-target organisms, including pollinators and natural enemies. In Asia a host of predators and parasitoids attack spotted lanternfly and assist in reducing populations of lanternflies in its native range. As of yet, the impact of natural enemies on this pest are largely unknown. Due to the intimate association between Tree of Heaven and spotted lanternfly, some growers are removing Tree of Heaven near their orchards and tree nurseries.
What can private citizens do to help? During the waning days of winter and in spring, keep an eye out for egg masses on tree trunks and other objects outdoors. The Pennsylvania Department of Agriculture has established a remarkable web site (link provided below) to assist citizens with identification of this new pest, to learn how to destroy egg masses, and to report sightings. If you discover an egg mass, nymphs, or adult lanternflies, report these to your University Extension Service or State Department of Agriculture.
In an ever-changing world where a global economy has resulted in a global biota, private citizens are likely to be the first ones to discover new invaders as they arrive and spread. You are the boots on the ground and have a role to play detecting and limiting the spread of the unrelenting legions of invasive species.
Factual details in this article came from the fascinating article “Lycorma delicatula (Hemiptera: Fulgoridae): A New Invasive Pest in the United States”, by S.K. Dara, L.E. Barringer, and S.P. Arthurs. 2015. Journal of Integrated Pest Management, Volume 7, Issue 1, 1 January 2016, pmw009, https://doi.org/10.1093/jipm/pmw009
More information on the spotted lanternfly can be found at the following websites:
Entomological Society of America: https://entomologytoday.org/2018/02/26/spotted-lanternfly-states-urge-citizens-report-sightings-invasive-insect-hitchhiker/