Common Forest Health Agents
Common Forest Health Agents
Several forest health agents common to the Inland Northwest are Douglas-fir beetle, pine bark beetles, dwarf mistletoe, pine engraver beetles, fir engraver beetle, western gall rust, root diseases, stem decays, and physical damage from weather and animals. Eliminating impacts to individual trees is nearly impossible, but minimizing their scope and impact throughout a forest area is achievable. A brief description of a few insects and diseases follows.
Douglas-fir Beetle
Douglas-fir beetle outbreaks are usually
initiated by catastrophic events such as blow down or winter breakage.
Downed or weakened trees are attacked and beetles build up large populations.
The next year, new generations emerge and attack susceptible trees in surrounding
stands. Damage in standing trees is greatest in dense stands containing
a high percentage of large, mature Douglas-fir.
Salvage of down or weakened Douglas-fir is a primary tool in preventing Douglas-fir beetle outbreaks. When attacks have already occurred removing standing green or faded infested trees will help reduce or prevent further damage in the area. The risk of Douglas-fir beetle damage is reduced when dense mature stands are commercially thinned.
Pine Bark Beetles
Four different pine bark beetles affect
the pine trees in the Inland Northwest area—western pine beetle, mountain
pine beetle, red turpentine beetle, and pine engraver beetle. The
beetles generally favor trees that are water stressed. Trees can
become water stressed during a drought or by having too many trees in an
area (overstocked). The bark beetle bores through the bark and lays
its eggs in the cambium layer between the bark and the wood; the cambium
is full of sugar and nutrients that feed the larvae.
Trees killed by bark beetles can often times be recognized as red trees in the stand that appear suddenly. A tree can turn from green to red within weeks. However, other indicators of bark beetle such as pitch tubes, boring dust, or frass on the bark of the tree would have been present for months. Red trees, themselves, are usually not a forest health risk. They are an indicator of what has happened in the stand and what may happen in the future.
The western and mountain pine beetles are considered major tree killers in Northern Idaho and Eastern Washington. Both prefer trees greater than 6 inches in diameter. Trees that they attack usually die.
Root Diseases
Root diseases are the most damaging group
of tree diseases. Diagnosis and identification is based on:
Dead and dying trees can be salvaged; however, rates of disease spread and tree mortality may not be reduced. There is some evidence that partial cutting increases the rate of mortality in root-diseased stands.
Recognizing the various insects and diseases
on your forest land and striving to keep forest land healthy is a worthwhile
goal. Salvage of blowdown timber from last winter and springs wind
events is very important. Please call Northwest Management, Inc.
if you have any concerns about the health of your forestland. We
can assist you in managing your property to achieve your management objectives.
Contact us today for a free consultation about the management of your forestlands, marketing of your timber products, wildfire control efforts, or prescribed burning needs. We also provide the region's best wildlife management, watershed management, and forest regeneration services. Explore our site and let us know how we can best serve you!