SALISBURY, Md. — If you thought kudzu vines were invasive, just wait until you meet the bug that bears their name.
William Lamb, an entomologist with the University of Maryland, gave farmers some bad news at the annual Lower Shore Agronomy Day Jan. 29. The event was organized by University of Maryland Extension and was held on one of the snowiest days this year on the Eastern Shore.
“The major agricultural concern is international trade,” Lamb said. Some South American companies are refusing to import American soybeans for fear the kudzu bug will spread to their countries. A project Lamb is working on related to the kudzu bug has been underwritten by the Maryland Soybean Board.
Kudzu bugs, also known as bean plataspid, kudzu beetle and globular stink bugs, are attracted to kudzu vines as a food source and as a place to lay their eggs. They are equally fond of soybeans and therein lies the rub.
“An infestation of kudzu bugs can reduce biomass by 33 percent,” Lamb said.
Since the Asian invader first appeared in Georgia in 2009, scientists have learned some things about the pest but are far from having a plan to bring it under control. It is a sap-feeding insect similar to the brown marmorated stink bug, but it behaves differently in that it is not a home invader.
Researchers have found that the kudzu bug is attracted to white surfaces, a characteristic they hope they can use to trap the bugs for study. In Georgia, researchers had success with a modified beetle trap, but it didn’t work well in Maryland. To discover if — or how — kudzu bugs have taken up residence in fields, researchers use a sweep net.
In spring, kudzu adults emerge from hibernation to feed on legumes, especially kudzu vine and early plantings of soybeans, which are closely related. Kudzu bugs also eat a variety of legumes and Wisteria, but show a clear preference for kudzu and soybeans.
“The insect’s piercing, sucking mouth parts can lay waste to as much as 20 percent of your crop when they reach high densities in the summer,” Lamb said.
There are generally two populations that reach adulthood per year and they reproduce by laying their small white eggs on the underside of kudzu or soybean leaves. By the time the insect reaches the larvae stage, their light brown color is virtually indistinguishable from the leaf without taking a close look.
Kudzu bugs lack natural enemies or damaging parasites. But researchers have discovered there is a native tachinid fly that will lay its eggs on the mature bug. When the eggs hatch, they will feed on their host and destroy it.
The USDA has considered importing the Asian platygastrid wasp as a potential predator for the kudzu bugs, but Lamb said someone jumped the gun and brought the wasp to the U.S. without permission, so monitoring its impact will be difficult.
Lamb’s team has been charged with preparing educational materials about the kudzu bug. He distributed a fact sheet to agronomy day attendees to help with field identification. He said his team had also surveyed kudzu and soybean patches, especially in parts of Maryland close to the Virginia state line, since the bug appears to be moving north.
Lamb gave farmers an update on what the team of University of Maryland scientists, working in cooperation with colleagues in other states, had learned in 2013 about the kudzu bug, with a projected distribution for 2014. Dorchester County on the Eastern Shore and several counties in southern Maryland, as well as Delaware and several counties in Northern Virginia, have already confirmed incidents of kudzu bug infestation.
“Kudzu vines are key to discovery,” Lamb said. He said the research team had located 41 patches with a low number of kudzu bugs in mid-June. By the end of summer, 17 patches were infested. Research suggests that two new generations of adults are produced each year, the last of which hibernates over winter and re-emerges in the spring to lay eggs in late June.
Last spring, researchers tried to catch adults for study in overwintering traps like the ones used successfully in Georgia. They were unsuccessful, but they plan on trying again this spring.
Much of the research is being directed toward developing an integrated pest management, or IPM, protocol to guide farmers for successful management of the pest. One strategy is to make farm areas inhospitable for kudzu bugs. This would include allowing natural enemies into a field, but researchers haven’t figured out how to accomplish this yet due to a lack of natural predators in the U.S.
Researchers have also learned that the threshold for spraying is low.
“When you find one immature kudzu bug in your sweep net, it’s time to spray,” Lamb said.
However, the use of insecticide does pose potential problems; insect pests often develop resistance to a product in as little as one generation. Information about the effectiveness, thus far, of various products can be found at the website, www.MDkudzuug.org.