Observations About Pine Mortality in Arkansas County

Submitted by Grant Beckwith, County Extension Agent – Staff Chair, Arkansas County

We have received several phone calls to the Arkansas County Extension Office this spring about pine trees that had green needles last fall now being brown and dead. (Picture 1) We reached out to Dr. Vic Ford, Associate Vice President – Agriculture and Natural Resources with the University of Arkansas System Division of Agriculture, to come to Arkansas County and advise on what is happening to the pine trees. Below is his report.

“I examined pine mortality at six separate locations across Arkansas County, accompanied by County Extension Agents, Grant Beckwith and Phil Horton. All the trees dying were loblolly pine. Loblolly pine is very tolerant to flooding during the winter and is not stressed unless the flooded conditions last into the growing season. About half of the dead trees show a proliferation of cones and is a reaction to stress and often before mortality. It takes cones two years to reach maturity because the primordia of the cones are formed in the bud two falls before the cone releases seed. Stressors during the previous growing season before the cone primordia formed lead to the proliferation of the cones. Stress factors are numerous and can be drought, saturated conditions, lightning, injury to stem or roots, soil disturbance around the roots, crowded conditions, pollutants, herbicide or other chemical exposure, and many other factors. The living trees around the dead ones showed various signs of stress.

Stress leads to insects and disease attack that will further weaken the tree. It may take years or over a decade before and tree dies due to stress. Ips beetles (1/8 to 3/8 inch long) are attracted to stress trees due to the release of certain terrapenes into the air. The beetles attack the trees by boring into the bark causing the pine to attempt to repel the beetle by using resin to pitch the beetles out of the tree. The remains of the battle can be seen by the pitch tubes left on the bark. (Picture 2)

If the tree is overly stressed, it cannot produce enough resin to repel the beetle and the beetle bores into tree and feeds at the cambial layer between the bark and the wood. Galleries left by this feeding of the adults and larvae can be seen by peeling the bark. The beetles lay eggs in these galleries and the larvae grow, pupate and emerge as adults. The evidence of emergence can be seen by the small round holes in the bark and is often called “buckshot holes” because it is reminiscent of some one shooting a tree at distance with very small shot.

The beetle introduces a blue stain fungus into the tree that will grow throughout the tree and clog the water conduction to the needles that will lead to death of the tree. All dead trees had “buckshot holes” and some still had pitch tubes.

Stress factors are additive, and an introduction of another stress can lead to the decline in tree health. Stresses like drought are always there and often stresses the pine tree to the point of Ips attack. The Mississippi Delta Region has seen similar stressors to herbicide drift that eventually leads to Ips attack and death. The trees observed during my visit mostly were not in areas where drift was a possibility, but they were in areas where a volatile herbicide could have reached them after application. This would be especially true if pines were sensitive the type of herbicide. It is not possible to determine if this was the cause of the decline.”

We would like to thank Dr. Vic Ford for his time spent inspecting the injured trees in the county and giving his diagnosis. Please contact Grant Beckwith (870-692-4445), Phil Horton (870-830-1624) or the Arkansas County Extension Office (870-659-2058) if you have questions or would like additional information. The University of Arkansas System Division of Agriculture offers all its Extension and Research programs to all eligible persons regardless of race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.