Green Horizons

Trees across the state have been stressed this year by winter ice storm damage, severe April freeze, and a long summer drought. As a result pine bark beetles are attacking weakened trees less able to defend themselves. Isolated pockets of dying shortleaf pine, ranging from a few individuals to several dozen trees, have appeared in late summer southeastern Missouri. Foliage starts fading and entire tree crowns turn reddish brown in a few weeks. In many cases, the beetles attack the upper trunk and limbs, and no evidence of attack is seen on lower trunks.

Pockets of shortleaf pine mortality are typically caused by Ips bark beetles attacking drought-stressed trees. Signs of attacks are reddish-brown boring dust (frass), pitch tubes (entrances) and a shot-hole pattern of exit holes on the bark surface, and galleries (tunnels) beneath the bark. These beetles also carry spores of a bluestain fungus that hastens tree death by blocking water flow in the outer sapwood.

The duration of Ips outbreaks in forest stands is often short-lived, lasting only one season. If infested spots are isolated and widely scattered, the best course of action often is to let the infestation die out on its own. Cutting and removing trees to stop the outbreak may actually accelerate it because harvesting produces fresh host odors (attractants), logging slash (potential breeding sites) and additional stress or injury to the residual trees.