The Spotted Lanternfly, an obscure insect from Asia, has recently established itself as an invasive species in Pennsylvania, where frantic efforts are being made to halt its spread.
The Lanternflies are a widespread group of insects in the order known as Hemipterans, or “True Bugs”. There are about 125 genera of Lanternflies in the Fulgoridae family which can be found from tropical South America to Africa, Asia and Australia, but despite their wide range they are obscure and little-known. The group was originally described by Linnaeus from a number of specimens that were sent to him from China. Some of these species have a beaklike head formed from fused mouthparts which they use to pierce the stems of plants for feeding, and it was a popular belief in China that these structures produced light and glowed at night. Although this was untrue, Linnaeus accepted the story anyway and dubbed them “Lanternflies”.
Like most Hemipterans, the Lanternflies are plant-feeders, using their sharp beaks to suck the juices from stems and leaves. Most of them are innocuous, but a handful of species are agricultural pests on fruit trees and crops.
One of these pests is the Spotted Lanternfly, Lycorma delicatula. This is a fairly large insect, about an inch long, which looks vaguely like a butterfly. Despite the name, it is not a fly either.
Unlike most insects, which go through a life cycle of larval and pupal stages, the Hemipterans hatch into nymphs which look like smaller wingless adults. Eggs are laid in a mass of grayish-brown wax which blends into tree bark, and hatch the following spring. The young nymphs are black with white spots, while the adults have a body and outer wings that are light grey with black spots. The inner wings are bright red.
In Asia, the insect itself is eaten by birds and small mammalian predators. Rather than flying, when escaping danger the Lanternfly prefers to make short hopping jumps. In China the species is widely believed to be poisonous and is used in traditional medicine: in reality it has no dangerous toxins and is harmless to humans. It is speculated though that the red colors may be a warning to birds that the bug is unpalatable.
Lycorma delicatula ranges naturally in India, China and Vietnam. Its preferred host tree is the Ailanthus or “Tree of Heaven”, which has been widely exported across the world as an ornamental. Female Lanternflies prefer the Ailanthus tree for egg-laying. But it can also lay egg masses on any outdoors surface, such as a wall or a wheel well or a piece of lawn furniture. In addition, the insect is willing to feed on a wide variety of plants, including domestic crops such as apples, grapes, soybean, grain, rose bushes, and trees and shrubs including walnut and maple—at least 70 different plants are known to serve as a food source. And that has caused all the problems.
In 2004, the Spotted Lanternfly was introduced into Korea, perhaps by hitching a ride on an imported Ailanthus tree. Lacking any of its natural predators there, it almost immediately became established as a serious pest by feeding on Korea’s extensive peach tree orchards and causing enormous damage to the industry. Within three years it had covered most of the country.
In September 2014, the species was found in Berks County, near Philadelphia PA. Older egg cases were also found indicating that the Lanternflies had probably arrived a year or two earlier.
Recognizing the danger that the insect could pose to Pennsylvania’s fruit and timber industry, state and Federal authorities immediately swung into action. An area of several counties in southeastern PA was declared a “quarantine zone”, and every effort was made to prevent the bugs from being carried to new areas. Checkpoints were set up at county borders to examine passing vehicles for hitchhiking Lanternflies, and it became illegal to move firewood, lawn mowers, RVs and other potential carriers out of the quarantine area.
The zone itself quickly grew from 175 square miles to over 3000. Businesses which export wood and plants were required to have certificates indicting they are Lanternfly-free. Residents were asked to report any insects they sighted and to kill them when found. Programs have begun that treat infected trees with pesticides. The strategy has been to remove the Lanternflies from the extreme edges of their range, then gradually move inwards towards the core population until it is eradicated. So far the USDA alone has spent almost $18 million to try to contain the threat.
But the invader has proven to be up to the challenge. By 2018, not only was most of southeastern Pennsylvania infested, but populations of Spotted Lanternflies had spread to surrounding areas in Virginia, Maryland, Delaware, New Jersey and New York. New York in particular is concerned about the effects if the pest reaches the grape vineyards in the Finger Lakes area, which is well-known for its thriving wine industry.
In an effort at potential biological warfare, wildlife officials are examining a tiny parasitic wasp, Anastatus orientalis, which kills large numbers of Lanternfly eggs and nymphs in its native China. Tests are being done to see if the wasp can be released into the infested areas to remove the bug without harming any of the native North American wildlife. Another option being studied is to remove the Ailanthus trees which the female Lanternfly prefers to produce eggs. But the Ailanthus is itself an invasive species in the US, and has proven difficult to get rid of. The wide range of introduced Ailanthus trees may well aid the spread of the Lanternfly.