A penny-sized green beetle may not sound like the stuff of horror movies, but the way Champaign-Urbana and other communities were once cleared of elm trees makes the emerald ash borer scary.
Dutch elm disease, which killed nearly 14,000 elm trees here from the mid-1940s to the early '70s, was caused by a fungus-spreading beetle that, like the ash borer, probably originated in Asia.
Many of those dead elms were replaced by ash, another tree popular with homeowners and developers of new subdivisions today.
This is the time of year to keep an eye out for signs of emerald ash borers, found in the Chicago area and Indianapolis in recent years, said Phil Nixon, University of Illinois Extension entomologist.
From late May to July, the beetles emerge from inside the trees where they pupate and feed for a couple years while growing out of their caterpillar- or wormlike stage. The pests chew up sugar and water processing areas of a tree, essentially girdling it, Nixon said.
The beetles are a bright metallic emerald green, about half an inch long and bullet shaped. While fairly distinct, Nixon said, they can be confused with other beetles – the tiger beetle for instance, and even some bees and wasps with greenish coloring.
The thing that makes emerald ash borers easily identifiable is the eighth-inch exit holes in the bark they make in boring out of a tree, which are distinctly shaped like a capital D, Nixon said.
While not prevalent in Illinois yet, especially downstate, ash borers have the potential "to take a nice shaded neighborhood and turn it into bright sunlight," he said. That's what happened in Michigan, where the beetles are believed to have entered the country first, probably hitchhiking in shipping containers.
"I've seen ash trees in Michigan that were 60, 70 feet tall, took two people to reach around the trunk, and they're deader than doornails," Nixon said.
In Illinois, the beetles were identified in 10 spots in Kane County and six in Northern Cook County last year. Estimates are that the invaders have killed 20 million trees in the Midwest, mostly in Michigan, said Champaign City Forester Bill Vander Weit.
"It's just a matter of time before it comes down here," he said.
Champaign has about 2,000 ash trees on city rights of way, about 10 percent of its 20,000 trees total.
"We strive to diversify our population as much as possible," Vander Weit said. "Those are the lessons we learned from Dutch elm disease."
Urbana City Arborist Mike Brunk said about 700 of the 13,000 trees owned by the city are ash.
"That's still a big hit if we had to remove them if we did get infested," Brunk said.
Urbana stopped planting ash trees a few years ago because of the ash borer threat, and the city is gradually removing unhealthy ash trees, which would be more susceptible to the beetle in the event of its arrival here.
Other than keeping an eye out for the pests if you have ash trees, and reporting likely sightings, using local firewood is perhaps the most important step residents here can take to curtail the possibility of an infestation, Nixon and the two city officials said.
Nixon said the beetles migrate less than a mile a year naturally. They need human transportation to move further faster, generally in infested nursery stock, which has been largely eliminated, or in firewood.
The rule of thumb is to buy wood from within a 50-mile radius of your home and not to bring any back with you if you go camping somewhere farther away.
Nixon said insecticides with the ingredient imidacloprid have proven effective in treating trees against emerald ash borers. But it is expensive – about $20 a tree homeowner-applied, more for professional application – and each treatment's effectiveness is limited to about a year.
Brunk said the best defense against the ash borer and other tree threats is a diverse tree population. In Urbana's case, the city tries not to let any one variety make up more than 10 percent.
"Under the Canopy," a pamphlet available through the city at libraries and the Urbana farmers' market, among other places, offers new tree suggestions and tree care tips geared to homeowners.