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Japanese beetle sightings in Ada and Kootenai counties spark warning from state

The Japanese Beetle has been sighted in Ada and Kootenai Counties more times than state officials feel comfortable with this year. The bug can be particularly harmful to rose bushes and lawns. File photo

The Idaho State Department of Agriculture is raising a red flag after increased sightings of the Japanese beetle, a pest that can feed on about 300 different types of plants.

The department, along with its federal counterpart, the U.S. Department of Agriculture, have been trying to keep the beetle from establishing a foothold in Idaho and other western states for decades.

But the last several weeks have led state officials to worry that more bug sightings in Ada and Kootenai Counties could mean that a population of beetles has made its way to the state, said Mike Cooper, Idaho Department of Agriculture plant industries division bureau chief.

“We’ve caught more in the last two weeks than we have in the last two years,” Cooper said.

High populations of the beetle can wreak havoc on various garden plants, especially roses and stone fruits. The larval form of the bug lives underground and feeds on the roots of the grass, which can destroy sod farm productivity and neighborhood lawns.

Cooper said that the sightings could be a fluke, but the department is asking for people who see the bug to send a sample of a dead specimen to the department. The state agency also has set out more traps, which will be seen around the university area in Boise, to see if they attract numerous beetles. The yellow traps are nontoxic, but the public should avoid them anyway, Cooper said.

“We’re doing everything we can right now to find out if we really have a problem,” he said.

Local nurseries say they aren’t too concerned about the Japanese Beetle yet, but the threat is on their radar.

Kevin Thibault, co-owner of the Du-Rite Nursery in Meridian, said there have been no beetle sightings in their grow areas, but they are keeping up with any state findings.

He said the worry is that the beetle could get established before nurseries are properly prepared.

“My understanding is once you see the beetle, the larvae is already in the ground,” Thibault said.

Tom Wilson, retail sales manager of Cloverdale Nursery and Turf in Boise, said there is not enough evidence of a threat to worry about the Japanese Beetle.

“It’s got to get pretty bad before we get too concerned about it,” he said.

Andrea Simao, Animal and Plant Health Inspection Agency program manager for the USDA, said the beetle has been on the East Coast for nearly 100 years already. The “front” of the moving beetle population — which can travel with plant shipments in trucks, by plane or slowly migrate west as it finds new food sources — is in the Midwest at the moment and sightings have remained rare in the West, Simao said.

She said high populations can eat leafy material to the point the material becomes skeletal and affects the plants’ ability to flower or grow fruit.

“If (the population) gets high enough you will see damage in your gardens,” she said.

But Simao stressed that serious damage only comes with a great number of the bugs in one area. There are many ways to protect against the pest’s effects, she added.

She said some chemical treatments worked well, but natural solutions like milky spore can interfere with the beetle’s grub stage and cause it not to reproduce.

Thibault said nurseries have to use chemical treatments and often are allowed to use different chemicals from those allowed for use by the general public. Still, he said, systemics — or insecticides sprayed on plants that become part of the plant’s natural makeup — are the best for dealing with unknown and unwanted pests.

With the Japanese beetle, people can’t skip any of their flora, however.

“It’s not like it is going to stay to one species (of plant),” Thibault said. “You pretty much have to spray everything.”

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