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Area bracing for ash borer

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Officials have discovered emerald ash borer beetles in two separate areas in Walworth County, according the state Department of Agriculture, Trade and Consumer Protection. The tree-killing insect hasn’t been found in Rock County, but workers plan to start searching.

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LAKE GENEVA — State workers will search along the state line in Rock and Walworth counties next week after two new infestations of the tree-killing emerald ash borer beetle were confirmed.

The infestations are in a tree in downtown Lake Geneva and in a private woodlot about 10 miles southwest of Lake Geneva near the state line, according the state Department of Agriculture, Trade and Consumer Protection.

The beetle has not been found in Rock County, but officials believe it's worthwhile to search in both counties, said Mick Skwarok, department spokesman.

"It just makes sense given Rock County's proximity to known infestations in Illinois," Skwarok said. "If we're going to do paperwork for Walworth County, we might as well do Rock County."

Skwarok said his department is limited in what it can do because of limited resources, but even so, it's too late in the season to set traps to determine how widespread the newly discovered infestations might be.

Jonathan Foster, a Lake Geneva city worker who spends part of his time as city forester, said he discovered the infested tree when doing some pruning.

Foster noticed the signs, including split bark, D-shaped holes the beetles leave when they emerge and the S-shaped galleries that the larvae leave under the bark.

Coincidentally, the state was confirming the rural infestation around the same time.

Emerald ash borers are an invasive species from Asia. They attack only ash trees, which have no natural defenses here. The beetles have now been discovered in 10 Wisconsin counties. The other counties are Brown, Crawford, Kenosha, La Crosse, Milwaukee, Ozaukee, Racine, Vernon, and Washington.

"Walworth County will be quarantined soon," according to a state news release. "Neighboring counties may be added to the quarantine pending further review."

For most people, the quarantine means that hardwood firewood, regardless of tree species, cannot leave the quarantine area.

The quarantine also affects some businesses that use certain ash products.

Residents in the area of the infestations are not required to do anything to combat the beetles, Skwarok said. Decisions about cutting trees or treating them with chemicals are up to the owners, private or municipal.

Scientists believe that in general, ash borers will spread between one-half mile to one mile each year.

Some cities have cut all their ash trees in an effort to stop the spread. Chemical treatments are prohibitively expensive if a large number of trees is threatened, especially in woodlots, Skwarok said.

"Some of the really good products that are administered by licensed professionals, they have a dollar amount attached to them. Some people can readily absorb that, and for others it's difficult," Skwarok said.

Foster said Lake Geneva has only about 300 ash trees on public property but many more on private land. More than 90 percent of city trees are not ashes.

The city probably will cut down smaller ash trees that become infested, Foster said, and he's hoping the city council will allocate money to chemically treat "specimen trees that mean something to us."

Foster said it's too late to treat trees now because of the beetle's life cycle, so treatments would start next spring.

The hope is to preserve trees until some tiny Asian wasps that are the beetle's natural predators can be released to control the population, Foster said.

"I think in a real practical sense it comes down to dollars: What can a community or an individual afford to do, and that is going to vary on a case-by-case situation," Skwarok said.

Skwarok said he knows of people in Walworth County who have been treating trees to protect them in case of an infestation, and he expects that activity will now increase.

EMERALD ASH BORER FACTS

Latin name: Agrilus plannipennis.

Nickname: EAB.

Home: China, Russia, North and South Korea, Japan.

Food: Only ash trees, including green, white, black, and blue ash, as well as horticultural cultivars of these species. Asian ash trees are the most resistant. The mountain ash and prickly ash are not true ash trees and are not affected.

Description: The adult beetle, which emerges from May to September—is about three-quarters the diameter of a penny, colored a metallic green.

Damage if they spread: A quarter of Wisconsin's urban forest is ash trees. States with the most to lose: Wisconsin and Minnesota, where the densest ash populations are in the north.

Most common way it moves: Hitching a ride with campers who transport firewood from infested areas. Quarantines in certain states and counties come with fines for violators.

Other ways they can move: They normally fly no further than one-half mile a year. Nursery-grown ash trees, wood packing materials such as pallets and ash hauled to make veneer or tool handles also could carry the beetles or larvae.

Possible symptoms of infestation: Branch die-off, growths of new branches from the tree's lower extremities, woodpecker damage, split bark.

Symptoms specific to EABs: "S"-shaped tracks under the bark, where the larvae have fed. Other borers make such tracks, but only the EAB makes the meandering "S" shapes. Also, D-shaped holes where the adults emerged from the trees. The flat side of the "D" is about one-eighth inch long.

Life cycle: Adults mate and lay eggs on bark. The eggs become worm-like larvae. The larvae chew their way into the trees and begin feasting, leaving behind S-shaped tunnels filled with frass, a mixture of fecal and plant material. Larvae transform into pupae in late fall.

More information: emeraldashborer.wi.gov.