Signs of Spring 7: Two Invasive Bugs

Photo by J. F. Orth, FLickr

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The spotted lanternfly (Lycorma delicatula) is one of the latest species in a long line of destructive, exotic insects that have invaded our agricultural and forested ecosystems. The lanternfly in spite its name is not a fly, nor is it, in spite of its often photographed spread-winged, moth-like appearance, a lepidopteran. It is a hemipteran (a true bug) with piercing, sucking mouthparts that is capable of doing great damage to a wide range of plants.

The lanternfly was first reported in Berk’s County in southeastern Pennsylvania in 2014. It is a native to China, India and Vietnam and is also a recent, and very destructive, invasive species in South Korea. It is thought to have initially entered Pennsylvania in 2012. In November 2014, the Pennsylvania Department of Agriculture established a quarantine of five townships in Berk’s County prohibiting the movement of firewood, lawn mowers, outdoor furniture, RV’s, wreaths, Christmas trees, etc. out of the area. This quarantine area has since been expanded to include a total of thirteen counties in the southeast corner of the state. The lanternfly is not a strong flyer and relies on human-aided transport to move significant distances, so this quarantine has been fairly effective in stopping the spread of this pest.

Photo by MTSOfan, Flcikr

Adult lanternflies are only 1 to 1 ¼ inches long and are fairly inconspicuous until they open their underwings to fly. The underwings are brightly colored (orange and red and white) and present a very distinctive, highly recognizable appearance. In the fall adult females lay eggs in grayish, mud-colored masses of 30 to 50 eggs that they attach to almost any solid object (including tree trunks and branches, outdoor furniture, rocks, etc.). The long list of objects enumerated in the quarantine regulations reflects the wide range of possible lanternfly egg deposition sites.

Eggs hatch in the spring, and the tiny nymphs (the first of four rapidly growing instars) find and feed on a wide variety of woody plants (including hardwood trees like willow, maple and poplar), pine trees, many types of fruit trees (including apple, plum, cherry and peach) and grape vines. The adults may continue to feed on this broad array of plant hosts but seem to prefer the exotic invasive tree called the tree-or-heaven (Ailanthus altissima) (see Signs of Fall 9, November 2, 2017). Large numbers of adult lantern flies and large numbers of egg masses can be found on tree-of-heaven, and proximity to tree-of-heaven in this quarantine area is major factor in the likelihood of finding lanternfly egg masses on surrounding objects.

Direct damage to the plants being fed upon by lanternflies can be severe, but even more extensive harm can be caused by secondary consequences associated with this initial feeding. Lanternflies feeding on a plant secrete a frothy substance called “honeydew.” The presence of this honeydew is often the way that a lanternfly infested plant is identified. This honeydew may attract other plant damaging insects and may also serve as the growth medium for some plant damaging fungi such as sooty mold.

Ongoing research at Penn State on these invasive hemipterans have involved genetic sequencing of the invasive population in order to determine the precise location from which they originated. Determining this location could then allow on-site evaluation of the native population to look for biological control agents like parasites, predators or parasitoids. The lanternfly’s microbiome is also being explored to look for potential pathogens or symbionts that may be useful in its control. The microbiomes of the plants on which the lanternfly feeds are also being evaluated to look for changes triggered by the lanternfly’s feeding and production of honeydew. The chemical ecology of the tree-of-heaven is also being examined to try to determine the exact nature of the lanternfly attraction and symbiosis.

Photo by D. Sillman

Another exotic invasive hemipteran that has been raising havoc in Pennsylvania is the brown, marmorated stink bug (Halyomorpha halys). These stink bugs are natives of northeast Asia (Japan, Korea, and China) and over the past twenty years have become a serious invasive pest throughout the United States. It is thought that this insect was first released into the United States in Allentown, PA in 1996. It apparently traveled from northeast Asia in a shipping container that was delivered either to the port of Philadelphia or Elizabeth, New Jersey and then trucked to Allentown. In 2001 this new, alien, invasive species was recognized and identified by entomologists at Cornell University, but by then large populations were being observed throughout eastern Pennsylvania, New Jersey and New York. This insect has now spread to forty states and is especially abundant in the eastern United States. It has very large populations in Pennsylvania, Maryland, Virginia, New York, New Jersey, Massachusetts, Delaware, Ohio, and North and South Carolina. Its spread to California and Oregon was allegedly via a car driven by a person traveling from Pennsylvania to California in 2005!

Many of these stink bugs find their way into our houses where they spend the winter months hibernating in tiny crevices and hideouts all around us. Their periodic emergence through the winter is often the only reminder that they are close by! Their mass emergence in May and June has become a very unfortunate sign of spring!

Brown marmorated stink bugs feed on over one hundred and fifty plant species including a number of crops that are of great economic importance to humans. Fruit trees (especially apple and pear), soybeans, and peanuts can all be significantly damaged by these insects. I have also seen adult stink bugs in my yard feeding avidly on the grapes growing on my grape vine.

Spider Eating Stink Bug  Photo by D. Sillman

I have talked in previous blogs about how local predators of insects (spiders and a variety of birds) have overcome their initial aversion to the protective secretions of these stink bugs and have begun to consume these slow moving bugs. Apparently, these emerging natural control systems in conjunction with increasingly sophisticated agricultural control regimes have reduced the overall impact of these pests considerably.

Dr. Greg Krawczk, a fruit tree entomologist and associate research professor in the Penn State College of Agricultural Sciences, says that the brown marmorated stink bug explosion peaked between 2010 and 2013 and that “we now know how to manage them.” In an October 25, 2017 article on the Penn State Newswire, Dr. Krawczk states that crop losses from these invasive bugs have been greatly reduced and that Penn State is exporting its knowledge and pest control technologies to many countries. For example, agricultural researchers from the Republic of Georgia are working with Dr. Krawczk and other scientists from Penn State, the USDA and Virginia Tech to develop programs to control their own recent explosions of brown marmorated stink bugs.

I hope the Georgian spiders and chickadee-equivalents learn how to feast on the bugs, too!

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