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Arkansas Loblolly Pine Decline

Members of the public can report pine tree discoloration and/or mortality by filling out this survey:

Loblolly and shortleaf pines are the only two native pines in Arkansas. Shortleaf pine has a range
throughout the state except in lowland areas. Loblolly pine occurs naturally in the southwest corner up
to the Ouachita foothills, and it is planted throughout the region. It grows in a wide range of
environments and is the major commercial pine in the southern U.S. Both species of pines exist as
natural stands, plantations, small stands, and yard trees.

Trees suffer from various stresses and modify their anatomy and physiology to adjust to the
environment. Drought is a readily recognized stress, but too much water, lack of mineral nutrients,
excess of various soil nutrients, air pollution, temperature, too high or too low of soil pH, root, stem,
crown disturbance, agricultural and other chemicals, lightning, and fire are stress factors that affect trees
and other plant life. Diseases and insects also stress trees, either directly or by taking advantage of a
previously stressed tree. An example of a direct stress caused by insects is the defoliation of pines by
redheaded sawfly. Ips beetles attacking pine trees that were struck by lightning is an example of pests
taking advantage of stressed trees. Stress is generally additive where the combination of factors results
in increased risk of tree death. Cold sensitive trees are more susceptible if they are under drought
stress. Trees are rarely killed by a single reason; a “decline” is a series of stresses that allow secondary
pathogens and insects cause tree mortality. Pine trees usually die from drought damage more rapidly
than hardwoods, but it has been documented that after severe drought it may take some trees up to 15
years to die as a result.

Looking at various pine tree mortality rates across the state, it is apparent that there are several factors
at play. First is the weather pattern that has included years of high rainfall with a period of about 3
months of severe drought. Trees build crown volume to match the roots capacity to provide water.
Periods of high rain result in lower root mass and higher leaf area. A severe drought that occurs almost
suddenly causes the roots to not support the crown that results in a moisture deficient stress that
attracts beetles due to volatile terpenes being released during stress. According to the US Drought
Monitor, 100% of the state was classified as “abnormally dry” or worse on the July 12, 2022 report, and
drought conditions existed in most of the state, peaking in mid-October. The second factor is flooded
soils during the growing season. Shortleaf is intolerant to any prolonged flooding, but loblolly can survive
flooding during the dormant season. The third factor is chemical exposure from drift or volatilization of
herbicides. Volatile herbicides, such as dicamba, can drift for miles in the presence of a temperature
inversion at the surface of the earth. In the Delta, the topography is conducive to daily temperature
inversions during the growing season. Herbicide drift from overspray of herbicides is always at risk of
being impacted due to vicinity to the site of application. Herbicide off-target affects are evaluated based
on an observable pattern of damage where the trees bordering the target crop are more symptomatic.
There has been an increase in the use of paraquat in field burndown before planting. Pines have very
little tolerance to paraquat, and other states have noticed pine decline next to fields where paraquat was

The last factor is the presence of foliar diseases on pines. In Arkansas, there are three major types of
foliar diseases: needle cast, needle rust, and brown spot needle blight. Infection occurs during wet
weather in the growing season. These fungi cause needle drop (typically observed in the winter and
spring months) and a reduction in growth, but it is not considered a perennial problem. Susceptibility is a
function of weather and the resistance of each individual tree. Some trees are more resistant although
there are no genetic screenings for this trait. In Alabama, it has been reported that brown spot needle
blight has been observed on every growth stage of loblolly pine. In some cases, stunted growth and
death have been reported after 2 or 3 years of subsequent defoliation. This is the same blight fungus
that infects longleaf pine and is controlled by burning.

Opportunistic insects such as Ips beetles, turpentine beetles, and root-feeding weevils attach to
weakening trees and often are the last stress that leads to tree decline. However, they are rarely the
only cause.

In summary, tree decline is affected by many factors. One factor alone generally does not lead to tree
death. Herbicide may be a factor on one site and not another. The presence of repeated brown spot
may contribute to the decline at other locations. The weather conditions have certainly played a role in
setting up stress and a severe drought following this wet period is detrimental to tree health.

This information was provided by Dr. Vic Ford, Associate Vice President of Agriculture and Natural
Resources at the University of Arkansas System Division of Agriculture Cooperative Extension Service, and
Chandler Barton, Forest Health Specialist at the Arkansas Department of Agriculture.