Feb. 28 2019 12:00 AM

It just didn’t get cold enough to kill them, experts say.

Debbie Miller, US Forest Service, Bugwood.org

“Cold enough for you?” was a common question this winter. For those hoping for a chilly end to a certain invasive pest, the answer was “No,” at least in the state of Missouri, according to a story by Greg Kozol published on the St. Joseph News-Press Now website.

The state was plenty cold to the humans living there, but not deadly enough to kill off emerald ash borer larvae hibernating under the bark of ash trees.

While states further north like Wisconsin and Minnesota were trumpeting that this years’ Polar Vortex had slowed the green tree-killer’s destructive swath, alas, ‘twas not the case a little further south. While the upper Midwest experienced mind-bogglingly cold temperatures of 30 degrees below zero and even lower, Missouri’s arctic winds were much milder.

Temperatures of 9 below were enough to shut down schools and stop mail service. However, experts say that the iridescent Asian pest will probably continue chewing through the Show Me state’s ash trees as soon as things start warming up.

“I would say most of the invasive species we see are pretty well adapted to survive our Missouri weather, unfortunately,” says 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.”

The emerald ash borer has been on a long, destructive road trip since it was first detected in Detroit in 2002. So far, it’s visited 35 states and the District of Columbia; Alabama, Arkansas, Colorado, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New York and North Carolina, killing millions of ash trees as it travels. It was first spotted in Missouri in 2008.

“You don’t want to relax on management,” says 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.”

Since its arrival in Michigan, probably embedded in a shipping crate, it’s killed 90 percent of the ash trees there. Missouri is expected to be less severely impacted, as ash makes up only a small percentage of the state’s forests.

But ash trees are a popular choice in urban areas for shade and landscaping. Golf courses, neighborhoods and property values could take a hit. There are clusters of ash trees at the Shoppes of North Village development and on the campus of 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.”

The University Extension is monitoring other damaging invasive species as well, like the like the Japanese beetle and the brown marmorated stink bug.

“There are several we are monitoring,” Fowler says. “They may be problems in the future. Some populations are in the building state right now.”

The walnut twig beetle is also of concern. That’s the bug that that spreads thousand cankers disease, which is what kills black walnut trees. These trees are commercially valuable in Missouri because of their strong wood and delicious nuts. So far, that disease been found mostly in western states and Tennessee.

Fowler and Messbarger say invasive species are hard to combat, because modern transportation moves much farther and faster than insects can fly.

“Humans make the spread of insects worse,” Messbarger said.