Pine Bark Beetle Signs, Life Cycle, and Damage
Several species of bark beetles breed in Great Plains pines, and once a tree is infested, group-killing of nearby trees is common.
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Identification
Larvae are usually C-shaped, legless, and white with brown heads. Adults range from 3 to 10 mm long and are brown or black.
Life cycle and overwintering
If winters are not severe enough, most bark beetle species can live over winter as adults, larvae, or eggs. Eggs are laid in galleries constructed between the bark and wood, and larval feeding galleries radiate out from these egg galleries.
The number of generations per year varies from one to three or more, depending on the species involved and the severity of the winter.
Signs of infestation
The first signs of attack are small holes in the bark, pitch masses on the bark, and boring dust in bark crevices and at the base of the tree.
Infested trees develop a characteristic blue-gray sapwood, caused by blue stain fungi that the beetles introduce as they bore. Feeding by larvae combined with the spread of blue stain fungi eventually girdles infested trees, and needles on girdled trees turn a characteristic reddish-brown color.
Why group-killing happens
Group-killing of trees is characteristic of all bark beetle species — once one tree is compromised, beetles frequently move to weakened neighbors, which is why prompt identification and treatment matter for the rest of a stand of pines.
