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Drought makes pine trees more susceptible to attacks

The drought of the past year, and its continuation, is having a detrimental effect on trees. As I drive down the roads in Gwinnett County, I see many trees dead or beginning to die. For pine trees, the drought has made them more vulnerable to pine beetles, small insects that can kill large pine trees, usually several trees in an area at once.

There are several species of pine beetles, and they are quite small, only a few millimeters long. Despite the small size, these insects have the potential to do enormous damage.

Black turpentine beetles infest the lower two feet of the trunk and potentially can spread up the tree to 15 feet. Southern Pine Beetles usually invade the upper part of the tree, while the Ips beetle infests the whole tree, from top to bottom.

Most species of pines in Georgia are susceptible to pine beetles, but loblolly, shortleaf and Virginia pines are most often preferred by the insects. The primary symptoms are the needles changing color from green to yellowish-brown. Pitch tubes, which look like popcorn, or larger-sized balls of resin, appear on the bark and sawdust accumulates at the base of the tree. The beetles bore into the tree, dig out galleries, and lay eggs. Their larvae begin feeding on the cambium, which is a layer of cells that produces the water and food carrying tissues of the tree under the bark. The adults also introduce a wood-staining fungus they feed on. The fungus clogs the vascular system of the tree causing it to slowly die. The adults emerge from the tree by cutting a small exit hole the bark and then flying to another tree. The beetles can have several generations per year. Once the beetles begin attacking the tree, they produce "pheromones," chemical scents that attract other beetles to the tree and nearby trees.

The bad news is that once the tree is infested with the beetles, the only course of action is to remove the tree. There are no chemical controls that can stop an infestation once it has begun. Sometimes chemicals 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 only a tree care professional can provide.

There are several methods of prevention that will reduce the likelihood that a pine tree will be attacked. Healthy, vigorous growing trees can fight the beetles by producing large amounts of sap to prevent them from becoming established in the tree. Keeping trees watered during times of prolonged drought will keep them in better health.

Give them roughly one inch of water a week. Do not dig around the roots, pile soil or other debris on top of the root zone, or drive equipment over the roots. These activities will cause compaction of the soil, limiting the amount of water and air flow in the soil causing root damage and death. Also, prevent mechanical damage to the trees by keeping lawn mowers and construction equipment away from them. Pine trees hit by lightning or have been damaged in other ways should be removed so they will not attract the beetles. If you are planning to prune the pine trees, do so between November and February to prevent the sap from attracting beetles. If you notice symptoms of pine beetles on your trees, contact a tree care company immediately to have the trees assessed, removed, and have preventative sprays applied if necessary.

Unfortunately, as the drought continues and potentially worsens, more and more pine trees will fall victim to these insects. For more information on pine beetles and license tree care companies in your area go to the following web link www.treesaregood.com or call the Gwinnett County Extension office.

Timothy Daly is an agricultural and natural resource agent with the Gwinnett County Extension Service. He can be reached at 678-377-4010 or timothy.daly@gwinnettcounty.com.