FOREST PROTECTION

Insects

Insects constitute the largest group in the animal kingdom. The great variety of species fills many roles in the ecosystem. The forest depends on insects for pollination and decomposition. Insects are also a major food source for other forest animals and other insects. Certain insects feed on tree foliage, seeds, or inner bark and wood, and spread tree diseases.

Damaging insects of concern to the tree growing industry can be categorized as defoliators, bark beetles and wood borers.

Defoliators eat leaves and tree needles (foliage). They are commonly the larvae of moths. When leaves are consumed, the tree's ability to produce food by photosynthesis is lost causing a reduction in growth and vigor.

Since conifers do not have the ability to grow all their needles back each year like hardwood trees, attacks by large numbers of defoliators can be lethal. Two important defoliators are the Tussock Moth and the Western Spruce Bud Worm. Both species cause more damage east of the Cascades than in Whatcom County.

Bark Beetles lay eggs in the bark of trees. The larvae, or grubs, bore extensive galleries in the layer between the bark and the wood and feed on the inner bark or cambium. These galleries reduce the flow of water and nutrients up and down the tree affecting the tree's health. The weakened tree may then become susceptible to other insect attacks and diseases. If the tree dies, its fallen limbs become fuel for fires.

Wood boring beetle larvae tunnel through the wood of weakened and dead trees creating holes that reduce the quality of milled lumber. These holes range in size from pinholes to 3/4" depending on the size of the beetle larva.We find all of these insects at low densities in the forest. Healthy trees are usually capable of withstanding minor insect attack. However, using bark beetles as an example, if a stand of trees is in a weakened condition from some other cause they may not be able to produce an abundant flow of pitch to push the beetles out. The bark beetles will then have enormous reproductive success, creating an epidemic population that can overwhelm even healthy trees. Under these conditions thousands of acres of trees can be damaged or killed. Acres of dead trees in turn create severe fire hazards.