Scientists offer advice for combating Bozeman pine beetle outbreak

“Mountain pine beetle larvae will continue to develop in dead standing or downed
trees, including small pieces of firewood,” said DNRC’s Tesmer. Larvae become
adult beetles in the summer, he said, emerging from their natal tree around mid-
July to take flight and locate living trees. The adults bore into a healthy host, lay
eggs, and the cycle begins anew.
“It can get expensive, but people who have beetle-killed trees need to consider
burning, chipping, burying or removing all of the infested wood prior to June 15,”
said Gannon. “Placing a tarp over infested wood doesn’t reliably kill mountain pine
beetles in our climate.”
Stover and Tesmer said they are looking into the possibility of a disposal yard where
Bozeman residents can drop off infested logs.
Healthy trees can be protected by spraying them next spring with any one of several
commercial brands of insecticide, Wanner said. “Just make sure bark beetles are
among the listed species on the label. Specialized equipment and precise
application are critical, so hiring a certified applicator is a good idea.” Thoroughly
covering the tree trunk is a key to success, he said; applications must be made on
all sides of the tree from ground level up to a five-inch caliper.
Another successful tool for preventing attacks is the chemical Verbenone, which
mimics the “no vacancy” message that beetles send out after an infested tree has
become too crowded to support any newcomers. The synthetic hormone is sealed in
a permeable plastic pouch – the pouch is stapled to the tree.
“Verbenone can be fairly effective in low populations,” Gannon said. “In residential
areas it’s best to apply 2 – 4 pouches per tree. Be sure to follow all label
instructions.” Verbenone can be ordered directly from the two companies that
manufacture the stuff: Pherotech (604-940-9944) and Synergy (604-454-1121).
Gannon said both companies have excellent Web sites with detailed information.
Identifying trees under attack by mountain pine beetles isn’t difficult. As they bore
into the trunk, the tree produces popcorn-shaped nodules of sap, called “pitch
tubes,” in an effort to repel the insects. Small piles of wood dust collect near the
base of the tree.
“Infested trees may remain green during the fall and have green crowns, but if you
see pitch tubes and wood dust, that tree is done for,” said Stover, “no treatment is
going to save it.” The feeding activity of the larvae will disrupt the tree’s circulatory
system, he said. Beetles also carry a blue-stain fungus which has a detrimental
effect on the host tree.
In Bozeman, mountain pine beetles thus far have gone after ornamental Scotch
pine and some spruce, said Stover, though all species of pine – ponderosa,
lodgepole, limber, Austrian, mugo and whitebark – are susceptible to attack.
Beetles target trees greater than five inches in diameter.