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Extracting a red oak borer beetle

A researcher extracts an adult red oak borer beetle from a tree in Arkansas for later examination

Research specialist Vaughn Salisbury of the University of Arkansas extracts an adult red oak borer beetle from a tree for examination in the laboratory. Scientists estimate that the inch-long insect has damaged about $1 billion worth of commercial timber in Arkansas and Missouri over the past three years.

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The red oak borer, an insect native to the Ozark National Forest in Arkansas and Missouri, lives most of its life cycle inside of oak trees. In recent years for unknown reasons, it has experienced a population explosion, causing the death of tens of thousands of trees in the Ozark forests. The insects have never before caused this kind of devastation and entomologists at the University of Arkansas are questioning what brought about the change.

Red oak borers have a two-year life cycle, most of which is spent inside a tree. Adult females lay their eggs under the lichens on the bark. The eggs hatch into larvae that bore into the bark and carve galleries in the phloem--a soft layer of woody tissue that lies beneath the bark. Later they migrate into the heart of the tree, chewing holes in the middle.

The trees can defend themselves against a few invaders--normally the average tree may have three or four adults emerge from its interior--but with the immense explosion in population, the attempt is futile. Researchers have seen as many as 700 to 800 emerging from one tree. The trees may look healthy for a while--sprouting green foliage--but by August, the top leaves turn brown, crumble and fall off, indicating the trees have become stressed.

Researchers are using modern technology to track progression of the problem. Satellite imagery can detect the presence and absence of chlorophyll in a given area, as well as give detailed data on the slope, aspect, vegetation type, soil type, and ridge top and valley locations in the landscape. This information, when combined with information on the age, density, diameter and vegetation composition of the forest, will be used to determine which forests have the heaviest infestations of the insect and see if it's possible to predict its spread. (Year of image: 2002)

Credit: 2002 University Relations, University of Arkansas

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