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Japanese beetles cause headaches for growers this time of year

BY SCOTT FITZGERALD, THE SOUTHERN

Monday, July 21, 2008 12:57 PM CDT

They've been migrating westward by land inch by inch since their arrival in 1916 at a Riverton, N.J., nursery in a carton of iris bulbs imported from Japan.

And much to the dismay of Southern Illinois growers and just about everyone who does nursery work, they are at peak population now, when it is hot and dry.

They are voracious feeders, eating just about everything on the green landscape.

"I don't know of any grape grower that doesn't express consternation about their presence," said Jackson County grape grower Mike Deuel.

Japanese beetles are a problem that appears to worsen every year, said Richard Cole, greenhouse manager for plant biology at Southern Illinois University Carbondale.

"There seem to be a lot this year. It varies each year, depending on the carrying capacity of the land," said Doug Jones, an integrated pest management specialist with the University of Illinois Extension.

In this particular area, Japanese beetles go after corn, soybeans and most fruit trees.

"They like the silks on corn. With plum trees, they will eat the fruit itself. They really like grapes. They are a menace to just about anything you are trying to grow this time of year," Jones said.

The metallic green-bodied insects feed on upper leaf tissue between the veins, creating a skeleton look to the leaf. They also munch on grass, leaving big brown splotches when they are done.

Japanese beetles caused $450 million damage to nurseries alone across the country in 2002, according to the Annual Review of Entomology.

Deuel said growers incur expense through eradication procedures such as spraying and other methods involving fuel costs.

What's tough about getting rid of Japanese beetles is they have very few, if any, predators.

"It's unfortunate. There are not an awful lot of predators that have developed a taste for them. And you've got to be cautious to bring something in," Deuel said about bringing in a predator such as a parasitic fly or wasp that has been used in the Orient to control Japanese beetle populations.

Meanwhile, spraying is effective now, but like all insects, the beetles could have the ability to develop insecticide resistance, he said.

Another effective method of eradication is using traps sitting on poles that lure the beetles in with a floral scent.

Jones has traps on his property and scoops out many dead beetles at night. It's an amount that has to be weighed, not counted.

Cole estimates traps he has set inside the SIUC greenhouse will garner anywhere from 2,500 to 3,500 beetles in a single day.

"They're unbelievable. I use traps in conjunction with spraying. Thankfully, we only deal with (Japanese beetles) for about six to eight weeks," Cole said.

If growers use traps to control the beetles, they should be careful of a "Catch 22" situation, both Cole and Jones advise.

The traps lure more and more beetles and any nearby vegetation is susceptible to their attacks.

"Keep (Japanese beetle traps) at least 40 to 50 feet away from your garden," Cole said.

scott.fitzgerald@thesouthern.com

351-5076