 The tiny mountain pine beetle can attack all pines native to the Swan Valley. The beetles lay eggs in the phloem layer of the inner bark where they create vertical egg 'galleries.' After the eggs hatch, the larvae travel horizontally during fall and winter, eating the phloem and eventually girdling and killing the trees. The larvae pupate and hatch in late spring. The adults then fly, looking for new host trees. The beetles also introduce the blue stain fungus, which interferes with the trees' water transferring system and speeds the trees' decline.
A mountain pine beetle infestation is recognizable by the light-colored reddish-yellow, half-inch diameter pitch tubes that form on the bark, giving the tree trunks a spotted look. Fine reddish-brown boring dust can often be found on the bark and at the base of the tree. By the time the pitch tubes and boring dust are visible, the trees are usually dead, although the needles may still be green.
Mountain Pine Beetle Management Options
Mountain pine beetles can infect entire stands of lodgepole pine, which tend to grow in dense monocultures. Thousands of trees may be attacked. Left alone, a dense beetle-infested lodgepole stand would eventually burn, the cones would open in the heat, new trees would germinate, grow and reach maturity, and the cycle would repeat itself.
Preventative thinning
Thinning young lodgepole, ages 15-20 years, to create 10-15 feet of space between trees, can reduce stress from competition and lessen the potential for an outbreak as the trees mature. In an older stand, thinning can reduce the possibility of a minor infestation. Yet, once a major outbreak is established, thinning is unlikely to be effective. Wind damage also can be a result of thinning.
Sanitation and Salvage
Removing affected trees before the beetles have flown (June - August) will reduce the number of beetles. Infected log decks and slash piles should be removed. Firewood should be split to dry and stacked away from live trees.
Lodgepole clearcuts
Clear-cutting or creating small, 2-10 acre clear-cut patches prior to a mountain pine beetle outbreak, are effective ways to capitalize on timber value and create space for young trees. Yet, wind can cause blow-down on the edges of clear cuts, especially at the top of ridges.
Creating resiliency
For long-term protection against mountain pine beetle, clear cuts and thinned stands can be converted to a diverse forest type by planting a variety of tree species that do not host mountain pine beetle. To build resiliency, a series of plantings over several years can produce an uneven-aged stand. If a forest is already diverse, mountain pine beetles may move through, creating dead standing trees and down woody material for cavity nesting birds and animals, nutrient recycling, and soil building without killing the entire forest.
Retaining economic value after an outbreak
Quickly harvesting trees after a mountain pine beetle outbreak can reduce economic loss due to the blue stain fungus, which infiltrates the water transporting system of the tree when the beetles attack. Blue stain affects boards aesthetically but not the strength of the lumber. It reduces the purchase price of the logs at the mill.
For more information visit
www.fs.fed.us/r1-r4/spf/fhp/mgt_guide/index.htm and www.beetles.mt.gov/. |
