By Lee Bergquist of the Journal Sentinel

An area in Vernon and Crawford counties in southwestern Wisconsin
appears to have a larger emerald ash borer infestation than Ozaukee
and Washington counties – the state’s only other site known to be
infected by the insect.

Wisconsin agriculture officials said a preliminary examination of
almost 7,000 purple traps hung on ash trees around the state shows the
invasive beetle hasn’t been detected outside the two areas.

That could change when crews start removing the traps in southern
Wisconsin in early August to analyze insects found in them, according
to Jennifer Statz, emerald ash borer program manager for the
Department of Agriculture, Trade and Consumer Protection.

The work will continue in northern Wisconsin until the end of
September.

Statz said Monday that the area of infestation in southwestern
Wisconsin covers about 6 miles.

The emerald ash borer was found in Victory, along the Mississippi
River in Vernon County, in early April, and was recently detected 6
miles away to the southeast in Crawford County.

The infestation near Newburg in Ozaukee and Washington counties
appears to be within 3 miles north and west of Highway 33 and county
Highway Y, she said.

All told, 6,893 traps were set in Wisconsin this year – one of the
largest such efforts in the country. The surveillance calls for a trap
every 1.5 miles over a 50-mile wide band from Marinette to Vilas
counties. The emerald ash borer had been previously found in the
eastern portion of Michigan’s Upper Peninsula.

The beetle was first found in Wisconsin last summer in Newburg.

Nationally, it was discovered in 2002 in suburban Detroit and is
believed to have arrived in wooden packing crates from Asia. Since
then, it’s killed tens of millions of trees in southeastern Michigan
and tens of millions more trees from Ontario to Missouri.

Adult beetles are metallic green and about one-half inch long. They
eat ash foliage but cause little damage to trees. The threat comes
from larvae, which feed on the inner bark and disrupt the flow of
nutrients of a tree.

Although chemical treatments have become available, an infestation can
kill an ash tree in just two years.

Milwaukee officials have decided to treat their as-of-yet uninfected
ash trees with a chemical injection, emamectin benzoate. Thus far,
crews have applied the pesticide on 7,500 trees, said David Sivyer,
forest services manager.