More than 600 species of bark beetles in the U.S. and Canada kill thousands of pine trees each year. There are guidelines for preventing the spread of bark beetles, but there is little you can do once your trees are infested. Different varieties of beetles kill trees in widespread areas of the U.S. For proper control, you need to identify the beetle infesting your trees.
Avoid Tree Stress
Avoid damaging the roots and trunk of your trees. Thin dense stands of trees so that the remaining trees are more vigorous and able to withstand infestations of bark beetles. Water around the outer canopy, not near the trunk of the tree. Water your tree twice a month during periods of drought. The water should penetrate at least 1 foot below the surface.
Prune Diseased Trees
Remove infested limbs or dying trees so that beetles don't move to nearby trees. Don't prune when bark beetles are flying. Don't prune pines from February to mid-October.
Some beetles like freshly cut wood and trees that are dying or have recently died. Get rid of that wood. Chip it or burn it. Cover firewood with clear plastic and put it under the sun to kill any beetles.
Predator insects won't eliminate bark beetles, but they can help. The blackbellied clend (Enclerus lecontei), the predaceous fly (Medetera aldrochii), the trogossitid beetle (Temnochila chlorodia), parasitic wasps and snakeflies will all attack pine bark beetles.
Once bark beetles have penetrated the bark, it is too late to control them with insecticides. Target beetles with chemicals when they land on trees and begin boring into the bark to lay eggs. There is no benefit to using insecticides to kill beetles on trees that have been attacked previously. You will only kill insects that are beneficial. Carbamates, pyrethroids and other insecticides can be applied before trees of value are attacked. Contact your state agricultural extension service or state department of agriculture for a list of insecticides registered to prevent bark beetle infestation.
Monitor Beetle Spread
If you know there are bark beetles in your area, you can use insecticides effectively, but you need to detect the beetles quickly. Semiochemicals are used as bait trap beetles. They are pheromones excreted by congregations of beetles or scents of trees that lure beetles. Seriochemical baits are placed in cardboard or plastic funnel traps that flying beetles see as a dark, cylindrical silhouettes.
To trap the Mediterranean pine engraver beetle, the U.S. Forest Service recommends a semiochemical attractant of Ipsdienol, 2-methyl-3-buten-2-ol and a-pinene. This beetle attacks loblolly, ponderosa and tamarack pines, plus Douglas fir and spruce trees.
The Forest Service recommends a-pinene and trans-verbenol to trap the red-haired bark beetle that infests Eastern white, jack, loblolly, lodgepole and ponderosa pines among other trees.
To trap the pine shoot beetle, use a-pinene and trans-verbenol. The pine shoot beetle attacks jack, loblolly, lodgepole, red, Scots, slash, ponderosa and Virginia pines.
Contact your local agricultural extension service or state department of agriculture on how to obtain and use these baits and traps.