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Kudzu bug is making presence known
Megacopta cribraria, also known as the kudzu bug or globular stink bug, is a pest insect that recently has appeared in the area. The bugs are much like the loathed brown marmorated stink bug. (Contributed photo by Joe Keiper)
Friday, December 6, 2013
By BEN R. WILLIAMS - Bulletin Staff Writer
Winter may be just around the corner, but that hasn’t stopped the kudzu bug from appearing in and around area homes.
Megacopta cribraria, also known as the kudzu bug or — aptly — globular stink bug, is a pest insect that has only recently appeared in Henry County and Martinsville, perhaps only this year.
According to Virginia Museum of Natural History Executive Director Dr. Joe Keiper, the hard-shelled grey insects, which are about as big around as the end of a pencil eraser, originally hail from Asia.
“Based on the genetics,” Keiper said, “the insects are all very closely related to one other in a familial sense. So basically, it could have been one female that got established over here, laid a bunch of eggs, and her offspring grew up and they mated together. What you have is a very genetically uniform population of insects that have been breeding prolifically in the last few years.”
There’s an emphasis on prolific; kudzu bugs are spreading surprisingly quickly. Keiper said the insects first were found in the U.S. in Atlanta in 2009, and they have been spreading from there ever since.
“Normally (with introduced insects) what you’re looking at is that the radius might increase naturally, say, a quarter mile per year,” Keiper said. “There’s a lot of variation in that; there are some insects that are terribly strong fliers, and there are others, like the gypsy moth, where the female is flightless. So that’s going to vary quite a bit.”
In the case of the kudzu bug, Keiper said, if it expanded its radius only a quarter mile per year, it would not yet be outside the Atlanta city limits. Instead, it has spread hundreds of miles across multiple states, and it seems to be preferentially headed northeast.
Keiper has a couple of theories about why the kudzu bug has spread so quickly — and is so difficult to eradicate — and both theories involve the reason it is considered such a pest: its food source.
Kudzu bugs, Keiper said, eat not only kudzu, but also soybeans, bean plants, sweet potatoes and various other farm crops. They do this by driving their tiny mouthparts into the plants and sucking out the juices, leaving brown spots and reducing the crop yield.
This part of the country, Keiper said, is dotted with large farms, providing the perfect feeding and breeding ground for the insects.
“A generation might be spent on a soybean field,” Keiper said, “but as they disperse from that soybean field, a certain number are going to wind up on wild plants, non-cultivated plants. Because of that, it’s going to be more difficult to target them.”
If the kudzu bugs ate only soybeans, Keiper said, it would be easy to eradicate them by spraying soybean fields with pesticides. However, because they can feed on a variety of plants, including plants such as kudzu that grow wild, it’s difficult to target them.
“They’re going to have to put pesticides on farm fields, and I understand that,” Keiper said, “but you can’t just go spraying broadly for them. It’s not like they’re transmitting disease or anything like that. They’re nothing more than a pest.”
The kudzu bugs aren’t only a pest to farmers. Much like the non-native brown marmorated stink bugs that also have seen a population explosion in Martinsville and Henry County, the kudzu bugs release a foul scent when they feel threatened. Some Bulletin readers have argued that the smell of the kudzu bugs is worse than the smell of the brown marmorated stink bugs.
Additionally, Keiper said, “they have the same kind of habit that stink bugs do. In natural situations, they’ll move into leaf litter and behind the bark of a dead tree, underneath logs and things like that, to hide out during the winter. But any crack or crevice will do, so they’re moving into people’s houses,” much like the brown marmorated stink bugs.
The kudzu bugs also can produce an irritating fluid intended to ward off predators. However, Keiper said, “apparently some people react badly to the fluid they release as a defensive mechanism. It should be just an annoyance that would normally deter a predator, but some people apparently kind of blister up a bit from it.”
Another reason Keiper suspects that the kudzu bugs have spread so quickly is that kudzu tends to grow along the sides of roads. Some of the kudzu bugs, he believes, probably hitch rides on passing vehicles and are introduced to new areas.
However, he doesn’t believe that these hitchhikers are solely responsible for the rapid spread, because their distribution would “become more spotty,” he said.
“You’d have hitchhikers that might travel for miles before they’re dropped off. In this case, it seems to be a uniform spread. I think a lot of it has to do with the explosive breeding potential of the critter. You’ve got the kudzu basically allowing them to spread with ease,” he said.
Because the kudzu bugs are new to the area, unanswered questions remain. For example, Keiper is not yet certain why the kudzu bugs seem to be active during colder temperatures that send the brown marmorated stink bugs scurrying for places to hide.
However, it seems likely that there will be ample opportunities to continue studying the kudzu bugs next year.