Campbell Vaughn: Beware pine bark beetles on the move

Last year’s floods, droughts and heat equaled a tough time for trees.  Be on the lookout for stressed pine trees.  Pine bark beetles are on the move and the can really cause big problems in forests as well as your own neighborhoods.

I was up at the lake a couple of week ago and found a recently deceased pine tree where you could see saw dust at the base. Getting close to the tree, I could actually hear a clicking from beetles chewing on the inside of the poor dead pine.

According to UGA’s own Forest Health Specialist Dr. Elizabeth Benton, weather-related stresses weakens trees, making them more likely to be attacked by bark beetles.  For instance, when under drought, trees do not receive enough water to perform their normal life processes, like converting sunlight to energy.

Tree drought responses include leaf wilting, early leaf fall, dying tissue, shutting down roots, and changing chemical process within the tree.  Many of these changes occur to conserve water and keep the tree from dying.  Even as rainfall conditions return to normal, trees require time to fully recover from their drought response.  So there can be a time-lag between increased rainfall and full tree health recovery.  Unfortunately, this time-lag and milder winter temperatures gives bark beetles more time to attack pine trees.

In Georgia we have three types of beetle that feast on pine trees, the Southern Pine Beetle (Dendroctonus frontalis), Ips Engraver Beetle (Ips spp.) and Black Turpentine Beetle (Dendroctonus terebrans).  All of the bark beetles have similar life histories. Usually, the adult beetles are attracted to trees under stress. They bore into the bark and hollow out areas where the females can lay eggs.  After about a week the larvae hatch and start feeding on the cambium layer.

Simply speaking, the cambium is thin layer of a tree that produces the vascular system that moves water and nutrients up and down the plant.  When the beetles mature, they pupate in cells constructed in the bark.  When the adults emerge, a small exit hole is cut in the bark and the beetles fly to another tree. Several generations are produced each year. Infested green trees are attractive to adult beetles.

The southern pine beetle is the most destructive forest insect in the South, and can also cause damage in urban settings. A lot of times an infestation can be 25 to 50 acres in size.  These type infestations can be catastrophic to timber growers.  Foresters have to remove huge quantities of timber to keep from losing stands of trees.

Southern pine beetle usually enters the trees from 6 to 30 feet above the base where the Ips beetle will attack any part of the tree. This means that spraying insecticides is almost completely ineffective. Once these two types of beetle are in the tree, the tree is going to die.

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To tell the difference between these beetles, southern pine beetles chew “S” patterns under the bark which is different from the Ips beetle that which has a pattern like an I, H or Y shape.  Both SPB and Ips can also infect the trees with a blue stain fungus that affects water flow and hastens tree mortality. Southern pine beetle and Ips may be present in the same tree. The other beetle is the black turpentine beetle and is not a major problem, only attacking a few stressed trees in the forest.  The turpentine beetles enter from the base of the tree up to about five feet.

The best control is to keep trees healthy which is not always easy in the landscape but very challenging in large acreage. Healthy trees will usually prevent the initial attack by adult beetles by creating a heavy flow of pitch (similar to sap) and can "drown" the beetles as they bore through the bark. It is not possible to prevent natural weakening factors such as old age, prolonged floods, fire, drought, and lightning strikes from occurring. However, in the homeowner situation, water and fertilization go a long way towards keeping the tree healthy. Avoid injuring trees with riding lawnmowers helps, too.

If you see the top dying out of a pine tree it is a goner. Check the base for sawdust which will confirm the presence of beetles. Then check your bank account to see how you are going to pay for a tree surgeon to bring in a crane to remove the dead pine before the beetles move to other trees in the yard.

This article originally appeared on Augusta Chronicle: Vaughn: Pine bark beetles are on the move looking for stressed trees