Mountain Pine Beetles
Mountain pine beetles (MPB) are the most important insect pest of Colorado's pine forests. MPB often kill large numbers of trees annually during outbreaks.
Trees that are not growing vigorously due to old age, crowding, poor growing conditions, drought, fire or mechanical damage, root disease and other causes are most likely to be attacked.
Trees attacked by mountain pine beetles are generally killed. Attacks may occur on individual pines or involve variable-sized groups of hosts. Normally, mountain pine beetles attack trees that are under stress due to competition with other trees, are weakened by pathogens, or are otherwise debilitated. Periodically on some hosts, large-scale outbreaks can occur and infestations can extend into stands of healthy trees.
For a long-term remedy, thin susceptible stands. Leave well-spaced, healthy trees.
For short-term controls, spray, cover, burn or peel attacked trees to kill the beetles. Preventive sprays can protect green, unattacked trees.
Mountain pine beetles develop in pines, particularly ponderosa, lodgepole, Scotch and limber pine. Bristlecone and pinyon pine are less commonly attacked. During early stages of an outbreak, attacks are limited largely to trees under stress from injury, poor site conditions, fire damage, overcrowding, root disease or old age. However, as beetle populations increase, MPB attacks may involve most large trees in the outbreak area.
We are targeting both the Denver Metro and the mountain areas for Beetle kill and IPS as well.
Signs and Symptoms of MPB Attack
Popcorn-shaped masses of resin, called "pitch tubes," on the trunk where beetle tunneling begins. Pitch tubes may be brown, pink or white (Figures 2 and 6).
Boring dust in bark crevices and on the ground immediately adjacent to the tree base.
Evidence of woodpecker feeding on trunk. Patches of bark are removed and bark flakes lie on the ground or snow below tree.
Foliage turning yellowish to reddish throughout the entire tree crown. This usually occurs eight to 10 months after a successful MPB attack.
Presence of live MPB (eggs, larvae, pupae and/or adults) as well as galleries under bark. This is the most certain indicator of infestation. A hatchet for removal of bark is needed to check trees correctly (Figures 3, 5 and 8).
Bluestained sapwood (Figure 9). Check at more than one point around the tree's circumference.
Control
Natural controls of mountain pine beetle include woodpeckers and insects such as clerid beetles that feed on adults and larvae under the bark. However, during outbreaks these natural controls often fail to prevent additional attacks.
Extreme cold temperatures also can reduce MPB populations. For winter mortality to be a significant factor, a severe freeze is necessary while the insect is in its most vulnerable stage; i.e., in the fall before the larvae have metabolized glycerols, or in late spring when the insect is molting into the pupal stage. For freezing temperatures to affect a large number of larvae during the middle of winter, temperatures of at least 30 degrees below zero (Fahrenheit) must be sustained for at least five days.
Logs infested with MPB can be treated in various ways to kill developing beetles before they emerge as adults in summer.
A Touch of Class Tree Service highly recommends that a professional service perform this service rather than doing it yourself. They have the high-pressure equipment, the personal protective gear, and can get restricted-use chemicals. If you choose to spray yourself, YOU MUST follow the label exactly, and dispose of the leftover spray and rinse water according to directions. Use only insecticides that are labeled for use to protect trees from bark beetle attack. These insecticide formulations have additives that bind the active ingredient to the bark. If you hire someone to spray, they must be a licensed applicator. Make sure to ask to see their license, and request references. Also make sure to get a commitment that they will spray before July.
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