Over the past year, the Extension office has received numerous phone calls from residents concerned about pine trees on their property that are turning brown. What could be troubling these trees?
A variety of problems could be causing them to suffer, such as drought stress, but some are infested with pine beetles, insects that are roughly 1/8 inch long, and despite their small size, they do enormous damage.
There are several species of pine beetles and pine trees become more vulnerable to these insects as a result of the lack of rainfall last summer and damage from construction activity. They are relatively inactive during the winter, but as the weather becomes warmer, the insects will become more troublesome.
Most species of pines in Georgia are susceptible to pine beetles. The primary symptoms are the needles changing color from green to yellowish-brown. Pitch tubes composed of pine resin, which look like popcorn, appear on the bark, and sawdust accumulates at the base of the tree. The beetles bore into the tree, dig galleries, and lay eggs. Their larvae begin feeding on the water and food carrying tissues of the tree under the bark girdling it. They also introduce a wood staining fungus for food, which clogs the vascular system of the tree, causing it to die slowly. The adult beetles cut a small exit hole the bark and then fly to another tree. Once the beetles begin attacking the tree, they produce chemical scents called ‘pheromones’ that attract other beetles to the tree and nearby trees.
Unfortunately, once the tree is infested with the beetles, the only course of action is to remove the tree. There are no chemical controls available to stop an infestation once it has begun. Sometimes pesticides can be applied to trees that have not been infested as a preventative measure. Only a licensed tree care company can do the spraying since it requires specialized equipment and expertise that only a tree care professionals can provide.
Keeping the trees healthy is the best way to reduce the likelihood of a pine beetle infestation. Trees produce large quantities of sap that help prevent the insects from becoming established in them. During dry spells, apply supplemental water to the trees tree at a rate of one inch per week. Avoid digging or trenching around the roots. Do not pile soil or other debris on the tree root zone. This can cause compaction, which restricts the penetration of water and air into the soil leading to the damage and death of roots. Also, prevent mechanical damage to the bark of the trees by keeping lawn mowers, construction equipment, and vehicles away from them.
If you observe pine trees that appear sickly, have a certified arborist assess to determine if the tree is infested with pine beetles or if the symptoms are the result of another cause. You can find one through the Georgia Arborist Association website at http://georgiaarborist.org.
Timothy Daly is a County Extension Agent with the University of Georgia Cooperative Extension, Gwinnett County. He can be reached at 678-377-4011or firstname.lastname@example.org