With summers devoted to eating and mating, the emerald ash borer might be the 1-inch equivalent of a boy in his late teens.
Winters are more laid back, with the larvae nestled behind the bark of an ash tree as the insects try to survive the long, cold winter.
Survive they did, despite last week’s extreme cold snap. Temperatures of 9 degrees below zero were enough to shut down schools and stop mail service, but the bullet-shaped, exotic insect from Asia carries on to continue decimating Missouri’s ash tree population as soon as the days turn longer and warmer.
“I would say most of the invasive species we see are pretty well adapted to survive our Missouri weather, unfortunately,” said Tom Fowler, horticulture specialist with University of Missouri Extension. “To actually kill an ash borer in a tree, it would need to be 25 below or more. We’d have to have longer sustained cold temperatures.”
It was cold last week, but not that cold. The ash borer, first spotted in Missouri in 2008, might have met its partial demise in Wisconsin and other Upper Midwestern states where the actual air temperature lingered at 30 degrees below zero or more.
In Missouri, at least for the purposes of invasive species, it wasn’t cold enough.
“You don’t want to relax on management,” said Lonnie Messbarger, a forester with the Missouri Department of Conservation. “Don’t assume this is going to kill off a bunch of bugs. It would be possible but not likely.”
The insect species destroyed up to 90 percent of the ash tree population in Michigan, where the borer was first spotted in the United States. The impact in Missouri is expected to be less severe, because ash makes up a small percentage of the state’s forests.
The tree is a popular choice in urban areas for shade and landscaping, so the loss of it could impact golf courses, neighborhood aesthetics and property values in some areas. Clusters of ash trees are at risk at the Shoppes of North Village and Missouri Western State University.
“It’s probably urban areas where you’re going to see the effects of the ash borer,” Fowler said. “It bores in and destroys the area right under the bark of the tree. They can do a lot of damage.”
Fowler said University Extension is monitoring other species and expects to see continued nuisances from the Japanese beetle and the brown marmorated stink bug.
“There are several we are monitoring,” he said. “They may be problems in the future. Some are in the building state right now.”
Of particular concern, he said, is the spread of the walnut twig beetle that causes thousand cankers disease. It kills black walnut trees, which are commercially valuable in Missouri because of their strong wood and flavorful nuts.
So far, that disease been found mostly in western states and Tennessee. According to Fowler and Messbarger, invasive species are hard to stop because modern transportation moves much farther and faster than insects.
The first emerald ash borer probably hitched a ride to the United States on a shipping container from the Far East, and it’s been a battle to save trees ever since
“Humans make the spread of insects worse,” Messbarger said.