Western Integrated Pest Management Center

 

September 2013 was a tough month for Boulder, Colorado.

First, a storm dumped nine inches of rain in a single day and caused extensive flooding in Boulder and other Front Range communities.

Then a city forester made the first discovery in Colorado of an Emerald Ash Borer, an invasive beetle native to Asia that's killed tens of millions of ash trees in the Midwest since first being detected in Michigan in 2002.

Boulder Assistant Forester Kendra Nash was marking a dead tree for removal, when her spray-painted “X” crossed a D-shaped exit hole characteristic of the insect. That discovery set in motion a multi-agency response to determine the extent of the infestation and a coordinated response to quarantine, control and contain the beetle if possible.

“It was a massive response with a lot of different agencies,” said Carol O’Meara, the Colorado State University extension agent in Boulder County. “The Colorado Department of Agriculture is leading the response.”

First the detection was confirmed by the USDA’s Animal and Plant Health Inspection Service and an initial screening found seven infested trees. The next step was a delimitation survey to determine the scope of the infestation.

“Boulder was divided into 38 one-square-mile grids,” O’Meara explained. “It was really up to the City of Boulder how they wanted the delimitation survey to look, and it chose the most comprehensive approach.”

Ten trees were selected randomly in each grid for inspection, and additional trees were sampled in high-impact areas. For each selected tree, two branches were removed, then examined by extension agents by painstakingly peeling each log into paper-thin layers using a draw knife.

“We spent two-and-a-half months in a forestry shed, peeling every single day,” O’Meara said.

Advanced Medical Imaging in Louisville, Colorado offered to conduct CT scans of the branches to help speed the process, but it didn’t work out because the cost was high and “our sitting in the medical lobbies with logs swaddled in blankets on our laps alarmed patients,” O’Meara said.

The survey identified four infested grids and allowed officials to set a quarantine area that encompassed all of Boulder County. (Beetles have now been confirmed in nine grids and Boulder is considered “generally infested” at this point.)

Setting the quarantine area and being able to advise people whether or not to use insecticides to protect their trees based on their proximity to known infestations was a priority, but researchers are learning important and unexpected things about the emerald ash borer and the trees it infests in the West.

“Colorado is the westernmost state with the insect, and we’ve learned a lot about how to recognize infested trees in the West,” O’Meara said. “Our trees don’t act like the trees in the Midwest.”

Because Western trees routinely deal with the effects of drought and higher solar intensities, they don’t show the same pattern of distress as Midwest trees, and often tolerate infestations longer, O’Meara explained.

“It’s hard to be a tree in the West,” she said.

For emerald ash borer resources in Colorado, visit the state Department of Agriculture website.