SPRINGFIELD, Ill. — State agriculture officials announced last week the emerald ash borer (EAB) has been found in two more counties in Illinois, bringing to 41 the number under quarantine.

It is an area that covers nearly half of Illinois, and the tree-killing beetle is showing no signs of slowing the pace of its infestation across the Midwest. The latest two counties, Knox and Henry, are in the northwestern part of Illinois.

The EAB’s larvae burrow into the bark of ash trees, essentially starving the trees to a slow death. The metallic-green beetle is native to Asia and was first discovered in Michigan about 10 years ago; ag officials now estimate the species has killed more than 25 million ash trees.

Once discovered in an area, the county remains under quarantine with penalties for moving any firewood past county lines. The transporting of firewood is the principal way for the EAB to spread.

“When you travel, don’t load up your camper with firewood, and by the same token, don’t bring it home with you,” said Jeff Squibb, spokesman for the Illinois Department of Agriculture (IDOA). “Use it at the campsite or leave it.

“The quarantine will stay in place until the entire state is infected or we find a product that can contain it. I think it’s safe to say that every ash tree is at risk.”

Beetles were discovered in Henry County at a park on the northwest side of Kewanee and on Knox College grounds in Galesburg.

While some pesticides have helped in the control of the beetle, a treated tree can still be infected. The IDOA recommends property owners contact the department or a local forester, if they believe they have an infected tree. In most cases, the tree likely will have to come down.

To help landowners identify the beetle, as well as other disease-carrying pests, the University of Illinois extension is offering its inaugural first-detector training program, with courses at five locations throughout the state in February and March.

Registrations will take place through those local extension offices, with details forthcoming in January. The courses will provide in-depth training on current and emerging pathogens and insects that affect trees.

The program will focus on the ash borer, thousand cankers disease and invasive plant species and will include identification/detection, life cycle/biology, management, commonly confused lookalikes and regulation.

The first classes will run from 9 a.m.-3 p.m. in Springfield on Feb. 12, in the Quad Cities area on Feb. 26, in Mt. Vernon on March 7, in Collinsville on March 14 and in Champaign on March 21.

The fee is $25 per person and includes lunch. For more information, call those counties’ extension offices.