U.S. Air Force Academy foresters battling beetles

  • Published
  • By Carole Chiles Fuller
  • AFCEC Public Affairs
U.S. AIR FORCE ACADEMY, Colorado --  A tiny insect is posing a monumental threat to the thousands of acres of Ponderosa pine trees on Air Force Academy property.

Fighting the gnat-sized ips engraver beetle is among the duties of Diane Strohm, natural resource manager and forester at the academy, and her assistant, forester James Donahey. They have a big challenge: The academy grounds encompass about 18,500 acres, and about 13,000 acres are forested. Ponderosa pines, the target of four of the 11 species of ips beetles in Colorado, account for 95 percent of those trees. Individual trees used in landscaping also are subject to infestation.

The beetles thrive in dry conditions, and Colorado has been in drought, off and on, the last 15 years, said Strohm. Clearing trees to reduce wildfire hazards may inadvertently help the beetle population boom: They love freshly cut trees and logging slash, or the debris left from cutting down trees.

"Drought reduces the trees' ability to respond to a beetle infestation," said Donahey. 
Normally, trees can fight off an infestation by pitching out, or flooding the beetles' tunnels. The last few years, Ponderosa pines have been losing that battle.

"Starting in about 2012, we took out 700 trees that were infested," said Strohm. "That went up to 1,000 in '13 and 1,100 in 2014. This year, fortunately, populations have dropped down to approximately 600. That's still very high for the ips beetle, but it's a positive trend."

Strohm attributes the downturn to abundant moisture in spring 2015 and to her team's aggressive control measures: finding infested trees, removing them and debarking or chipping them up before the beetles can emerge and attack more trees. Quickly identifying infested trees is important because these beetles can reproduce every eight weeks.

"They are polygamists," said Donahey.

The male constructs a chamber beneath the bark of a tree and attracts multiple females, who create egg galleries radiating from that "nuptial chamber," he said.  The larvae hatch and create more tunnels, eventually killing the tree. The first sign of damage, a fading tree crown, appears about the time the young beetles are ready to find a new victim. 

"We need to be very vigilant in finding these trees and treating them ... to prevent additional spread," said Strohm.

Recently, the foresters gained an ally.

"We're starting an innovative partnership with a cadet Capstone course, which is a group of senior cadets gathering together to try to solve a problem. We are looking at employing aerial reconnaissance to help us do frequent monitoring of forest health problems, in particular the ips beetle," said Strohm.

They plan to use winged aircraft outfitted with cameras to fly over the grounds every three weeks. Using spectrometry, areas that need to be field-checked will be identified.

"We have had a couple of test flights so far and are still working on getting this program going, but the idea is to help us identify areas for on-the-ground monitoring," she said.

Flights are expected to resume in the spring, when the beetles emerge from spending the winter on the forest floor or in infected trees.

"The money that we are spending looking for these trees and treating them is a very sound investment. We are taking out the trees rather than letting an infestation spread and dealing with the consequences in the future," said Strohm. "It's very important to be proactive with our resources."

Engraver beetles, including the ips, are a nationwide problem. Home- and land owners can help control their populations by taking these measures:

- Watch for damaged trees. Look for a change of color in the crown, or evidence of the tree creating pitch tubes.

- Look for frass, which Strohm describes as a combination of beetle scat and sawdust. Look for little reddish brown to orange sawdust in the crevices of the bark, at the base of the tree or on firewood.

- Prune accessible infested branches and chip them to kill beetles.

- Recently cut trees and logging slash are the prime attractant for the beetles. Chip them up, debark them or cover them in plastic and solarize them.

- Do not stack firewood close to living trees.

"If you have green firewood, that's an attractant for beetles, and they will spread to the trees it's stacked against, or spread to nearby trees," said Strohm.

While the foresters are making progress in the battle against the ips, they are monitoring threats from the Douglas fir tussock moth and the Western spruce budworm. 

"There are two populations which have caused extensive defoliation. On the Academy, we have been doing egg mass surveys to try to see if we have a population coming close," said Strohm.

"Right now our populations are low enough that we are not looking at control measures except for some landscape trees. We're trying to be very proactive in monitoring for these new upcoming pests. They are cyclical; they tend to be around every seven to 10 years. It just looks like this outbreak, particularly of the tussock moth, is more serious than we've seen in recent years. We are watching that closely," she said.