Slender spotted lanternflies like this one that landed on a small twig just before I snapped this photo are often flight capable, unmated females searching for suitable host plants on which to feed and produce batches of eggs.
Last week weather radar stations reported unusual low altitude clutter over several locations in the Mid-Atlantic region. News outlets including the Washington Post proclaimed that “So many spotted lanternflies are out right now, you can see it on radar.” To catch up with this story a bit, this week we will update parts of an episode first published in September 2020.
Lanternfly adults and their youngsters, called nymphs, remove large quantities of phloem sap from woody plants as they feed. The excess is excreted from their rear end in copious amounts as a sugary waste product called honeydew. More than 100 plant taxa of woody and herbaceous plants serve as hosts for spotted lanternflies. Spotted lanternflies can be severe pests of fruit and shade trees, grapes, and hops. Massive infestations in vineyards have withstood repeated applications of insecticides and still caused the demise of entire vineyards. In home landscapes, hundreds of these rascals have been observed feeding on a single plant, where they rain scads of honeydew onto vegetation and the earth below. As with honeydew produced by other phloem feeders such as soft scales and aphids, the honeydew excreted by lanternflies fouls foliage, fruit, and underlying plants, and serves as a substrate for the growth of a fungus known as sooty mold. Honeydew makes leaves sticky and fruit unmarketable, and sooty mold further disfigures leaves and fruit and may impair photosynthesis. This presents a huge economic problem for growers of apples, cherries, peaches, and grapes. Sweet honeydew and its fermentation products also attract a variety of stinging insects like yellowjackets and paper wasps.
Rotund spotted lanternflies like this one with a bright yellow underbelly are generally mated females with limited flight ability.
How far do spotted lanternflies move? The immature stages called nymphs don’t move all that far. A clever study conducted by Kelli Hoover and her colleagues at Penn State found that some spotted lanternfly nymphs travel as much as 213 feet in their quest to find a suitable host, but only about half traveled 56 feet. However, studies by scientists in Pennsylvania reveal some of the secrets to the longer distance autumnal movements of adult spotted lanternflies. Thomas Baker and his colleagues at Penn State discovered that slim fancy flyers are primarily unmated females capable of flights ranging from roughly 30 to 150 feet. Their spontaneous flights are believed to be quests to find suitable host plants that will supply sufficient nutrients for them to fatten up and deposit a complete complement of eggs before cold weather puts an end to their mischief. The Penn State team also assessed the flight worthiness of plump yellow-bellied lanternflies commonly found on hosts like tree of heaven. A vast majority of these heavy females had successfully mated but their ability to fly was weak and limited to only about 12 feet when launched into the air.
To see spotted lanternflies in flight and see why they are showing up on radar, please click this here (Courtesy of Cornell Integrated Pest Management). Radar sightings of insects are not all that unusual. Four years ago in 2021, during the emergence of Brood X periodical cicadas, cicadas in flight were captured on radar in the DMV. Swarms of devastating locusts in Africa and Asia are often tracked on radar.
While spontaneous autumnal flights have been witnessed on a regular basis, these relatively short distance flights of hundreds of feet likely account for only a minor component of the spotted lanternflies’ prodigious spread in the eastern United States. From their initial discovery point in Berks County in 2014, it has moved more than 650 miles and established populations of spotted lanternflies have been discovered in Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, West Virginia and, of course, the District of Columbia.
This map shows the current locations of established infestations of spotted lanternflies (blue counties) throughout the eastern United States. Map courtesy of Brian Eshenaur and the New York State Integrated Pest Management Program of Cornell University.
Spotted lanternflies are on the wing to find new host plants, bringing them in contact with the human-built world where they will wander buildings and benches in search of food. Many will perish of starvation or dehydration on sidewalks and in parking lots. Others will be squashed beneath feet and automobile tires. Some may visit shoppers and diners briefly before flying off, while others will be snared and killed by urban spiders. Before you leave a parking area infested with lanternflies, inspect your car to make sure these clever vagabonds are not hitching a ride with you.
Non-descript lanternfly egg masses are easily overlooked.
According to entomologist Julie Urban, the most likely explanation for these long-distance peregrinations lies in human-assisted transport of lanternfly eggs. It is believed that spotted lanternflies arrived in Pennsylvania around 2012 from Asia in a shipment of stone products bearing lanternfly eggs, a trip of some 7,000 miles. Unlike many herbivorous insects that lay eggs on food plants for their young, spotted lanternfly mothers often deposit egg masses on human-made non-host objects including stones, cinder blocks, lawn furniture, pallets, and vehicles, in addition to trees. These rather nondescript egg masses are easily overlooked on natural and human-made items and transported inadvertently by road or rail, moving this invasive pest significant distances and accounting for a major component of the long-range spread of spotted lanternflies.
So, how far will spotted lanternfly spread in the US? Based on climatic data from the US and Asia, scientists suggest that much of the eastern United States and portions of California, Oregon, and Washington State have climates suitable for the survival of spotted lanternfly. This is not good news for the magnificent and economically important grape growing regions in our western states. Will spotted lanternflies soon be coming to your neighborhood? Time will tell, but as I have often heard, you can usually bet on the bug.
This map shows the potential distribution of spotted lanternfly in the United States based on climatological data. Areas with the highest probability of supporting lanternflies appear in dark orange and areas unsuitable for lanternflies are white. Map courtesy of the Entomological Society of America at Entomology Today, October 3, 2019.
To learn more about spotted lanternfly please visit the brilliant, fact-packed Penn State Cooperative Extension Website at this link: https://extension.psu.edu/spotted-lanternfly
Acknowledgements
Bug of the Week thanks Dr. Shrewsbury for spotting and wrangling spotted lanternflies for this episode. Thanks to Jessica Kronzer for providing inspiration for this story. We acknowledge the great work of scientists contributing to our knowledge of this pest, with particular thanks to authors of articles used as references, including Flight “Dispersal Capabilities of Female Spotted Lanternflies (Lycorma delicatula) Related to Size and Mating Status” by Michael S. Wolfin, Muhammad Binyameen, Yanchen Wang, Julie M. Urban, Dana C. Roberts, and Thomas Charles Baker, “Worldwide Feeding Host Plants of Spotted Lanternfly, With Significant Additions from North America” by Lawrence Barringer and Claire M. Ciafré, “Perspective: shedding light on spotted lanternfly impacts in the USA” by Julie M. Urban, “Dispersal of Lycorma delicatula (Hemiptera: Fulgoridae) Nymphs Through Contiguous, Deciduous Forest” by Joseph A. Keller, Anne E. Johnson, Osariyekemwen Uyi, Sarah Wurzbacher, David Long, and Kelli Hoover, and “The Establishment Risk of Lycorma delicatula (Hemiptera: Fulgoridae) in the United States and Globally” by Tewodros T. Wakie, Lisa G. Neven, Wee L. Yee, and Zhaozhi Lu. Thanks to Brian Eshenaur and the entire team at the New York State Integrated Pest Management Program of Cornell University for providing the updated maps of spotted lanternfly in the US and to the Entomological Society of America for providing the map of the potential distribution of spotted lanternfly in the US.