A pesky beetle has been moving across Missouri, damaging fields, shrubs and fruit crops.
The Japanese beetle, which was introduced into the United States from Japan around 1916, likely came to the Midwest in a shipment of flowers or shrubs. The pests then spread to St. Louis, Kansas City, Springfield and Columbia during the 1940s in their pupal stage — white grubs lurking in potted plants used for golf courses — said Wayne Bailey, an MU Extension associate professor of entomology.
In recent years, they’ve been spreading from their four original locations to southern areas of Missouri.
Jay Chism, an agronomy specialist with MU Extension, said the beetles are appearing for the first time in Barton County in "significant numbers."
"Last year, I didn't catch a handful of them for the whole season," Chism said in an interview with the The Joplin Globe. "Last week, I caught 600 beetles in two days. Then, four days later, I caught 1,100 more."
That doesn’t mean they’re moving out of Columbia, where the beetle population has “increased exponentially,” Bailey said. He said he’s gotten a few calls from soybean farmers and landscapers, whose ornamental plants are some of the beetles’ favorite foods.
Wineries also tend to have a tough time combating the pests because of the bugs’ penchant for sugary grape juice. Cory Bomgaars, head winemaker at Les Bourgeois Winery, said he’s started to see beetles in the vineyards over the past couple summers.
He said the amount of damage the beetles do to the vines is “pretty mild.” New vines, though, haven’t had a chance to develop as many shoots and leaves as the more established plants, so the plant suffers the most damage.
Workers at the winery have tried using traps to rid vines of the beetles, but the results were sometimes unwanted.
“The traps, we found through a lot of research, are attracting as many as you trap, so the population actually increases in the area,” he said.
For homeowners looking to protect their roses and any of the other 219 North American plants the beetles love to eat, Bailey suggests looking for traps at gardening stores. Most combine pheromones and the scent of roses to attract both male and female beetles.
Les Bourgeois uses carefully timed and targeted bouts of insecticide to control the population, Bomgaars said.
Chism said insecticide works to rid gardens of pests, but dousing plants with a morning bath of soapy water is a more environmentally friendly method. He also suggests using a cheesecloth or a similar protective barrier over garden plants, but even those measures might not be enough to get rid of all the beetles.
“They are an insect that is rarely killed, but they’re not a difficult insect to kill,” Bailey said. “It’s just more of a problem that they overwhelm whatever insecticide you’re using by sheer numbers. You’re killing 95 or 90 percent — you’re never killing all of them.”
Although the peak of beetle season is typically around July 10, and numbers on the MU pest monitoring website are beginning to show a downward trend in Boone County, this year’s season is expected to run a little longer than normal, Bailey said.
“I really think we still have a situation where the high numbers will remain for a while,” Bailey said. “We would expect to see them around the state and Columbia until the third or fourth week of July, maybe even August.”
The pest is easy to identify but is confused with another insect common to the area, the June beetle. The Japanese beetle is about half an inch long and about half the size of the June beetle.
The Japanese beetle is metallic green, with bronze- or copper-colored wings. They also have five white tufts of bristles that run alongside the shell.
Chism advised people to be alert and report any infestations to the county extension office.
"If you can control the early ones, it is less likely that large mobs will come in and take over an area," he said.
The Associated Press contributed to this report.