Life in 1916

Des Moines Register: Japanese beetle munching away on Iowa plants, trees with fury
Kirkwood Community College in Cedar Rapids has spent hundreds of dollars in the past few years spraying its cherished vineyard to control a colorful but unwelcome invader that is munching trees and plants over much of Iowa.

Japanese beetles took a long time to reach Iowa — they were first spotted in the United States in 1916 from nursery stock in New Jersey.

But they are now making themselves at home here with a fury, documented in 55 counties. That includes three that discovered the pests for the first time this year — Poweshiek, Fremont and Humboldt. Last year, Audubon, Carroll, Cherokee, Hamilton, Harrison and Ida joined the list.

In 2008, only 25 Iowa counties had Japanese beetles. In 1994, only the Davenport area had recorded the beetle, which feeds on the leaves of 300 tree and plant species and on grass roots.

“They are continuing to expand their territory,” said state entomologist Robin Pruisner. “There is not a lot you can do to stop them. I call them flying little tanks. They seem to bounce back from treatments.”

The beetles usually don’t kill healthy plants, but they can reduce production on a grape vine. If a tree is weakened, the beetle’s leaf-munching ways are just one more invitation to disease, Pruisner said.

Iowa’s resurgent wine-grape industry is particularly on guard.

“They are a major threat,” said Tom Moore, Kirkwood’s wine-grape authority. The school has a vineyard and a winery and sprays pesticides weekly as needed to kill the beetles.

“If you don’t treat for them, you would lose your vineyard,” Moore added. The beetles also like to eat soybeans, Linden trees and grapevines from top to bottom. They don’t dine on the grapes, but they can reduce yields.

They are trespassers spreading across the Midwest and expanding their range out West after firmly establishing their territory along the East Coast.

The beetles can be knocked down with pesticides, but even that leaves a mess.

“One year we had a solid layer of dead beetles,” Moore said. “You couldn’t see the ground.”

Homeowners sometimes buy traps for the beetles. It’s a bad idea.

“They tend to bring more of the beetles in than they trap,” said Pruisner.

Linden trees and grapevines are like chocolate to these little guys, but they regularly eat the greenery of more than 300 species of trees and plants, including roses.

“I usually look at the poplar trees,” Pruisner said of her checks for infestations. “They are like a hot fudge sundae to them.”

Mike White, Iowa State University’s wine-grape expert, said 10 to 15 percent of Iowa’s 300 vineyards get damage bad enough to spray for the pests in any given year. Those operations feed 92 wineries statewide.

It’s a high-visibility problem.

“You don’t have to look for them, they are just everywhere,” he said.

The beetles quickly spread to Davenport, Muscatine, Cedar Rapids, Des Moines, Ames and Council Bluffs once they found their way over the Mississippi River.

“That is where we are seeing the biggest problems, because they’ve been there the longest,” White said.

Iowa State University entomologist Laura Jesse said the initial shock wave of the beetles may ease in coming years.

“When a new insect moves into an area, we have explosions of numbers,” Jesse said. “Over the next decade, the natural controls or parasitic insects will catch up with the population.”