Ips bark beetles have already devastated acres of piÃ±on pines in southwest Colorado. Soon, the beetle may launch an attack on Moffat County trees as well.
Ips beetles have lived in parts of Rio Blanco County for years. While working with the U.S. Forest Service in Grand Junction, John Denison said he has often seen dead stands of piÃ±on pine atop hills, signifying the presence of the beetle. But ips beetles have always existed there in natural balance with that region.
"The concern now is epidemic levels in southwest Colorado," Denison said. "Huge areas of trees have been killed."
The mountain pine beetle has long been a scourge to Colorado, killing millions of ponderosa and lodgepole pines. But ips beetles have become more prevalent after years of drought conditions have weakened piÃ±on pines. Ips beetles rarely attack healthy trees, preferring weak trees suffering root injuries or other stresses.
However, if a population gets strong enough, it will begin to attack healthy trees. Denison said the beetle has been reproducing four times a year at lower elevations. One female can produce 30 to 50 beetles.
"A population can build quickly," Denison said. "Literally, in a period of two years, it went from endemic to epidemic."
Terry Wattles, district forester in Steamboat Springs, oversees U.S. Forest Service land in Routt, Jackson and Moffat counties. He said Moffat County would be at the highest risk of ips beetle attacks, because private lands here are at a lower elevation and piÃ±on pines are more abundant.
Adult ips beetles winter under the tree bark or in litter surrounding the tree base, according to a report by W. Cranshaw and D. A. Leatherman for the Colorado State University Cooperative Extension Office.
In the spring, the beetles emerge and begin to attack weakened trees. The male constructs a cavity under the bark, known as the nuptial chamber. After mating, the female digs egg galleries off the central chamber. The larvae that soon hatch will mature into quarter-inch grubs, white to dirty gray, legless and with dark heads. They'll tunnel small galleries themselves, producing discolorations in the tree and eventually killing it.
The Forest Service and Bureau of Land Management are treating the ips beetle epidemic as a natural phenomenon, Denison said. Like wildfire, this is a way for forests to thin themselves.
But homeowners can protect their trees by thinning dense clumps of piÃ±ons. When piÃ±on roots must compete against other trees for moisture, they become weak and therefore more susceptible to ips beetle attacks.
Slash produced by thinning should be removed from the vicinity of valuable trees. Chipping or debarking will destroy any ips larvae living in the slash. Slash can also be scattered to promote rapid drying.
Particularly valuable trees can be treated with approved insecticides, Denison said. Insecticide treatments, such as permethrin or carbaryl, should be applied before wintering adults emerge for spring, typically when afternoon temperatures consistently reach 50 to 60 degrees. No treatment exists for trees already infested by ips beetles.
Rob Gebhart can be reached at 824-7031 or by e-mail at firstname.lastname@example.org.