The winter is passed by larvae in varying stages of development within the tree. In the spring, they change to pupae in their burrows, emerging as adults during the spring and summer. The female beetles deposit their eggs in cracks or bruises in the bark. The larvae which hatch from these eggs feed during the remainder of the season and pass the winter. There is only one generation each year.
Figure 22. Adult twig girdler and characteristic injury to twig.
Control.—The beetles are attracted to trees or areas of trees in a devitalized condition, induced by transplanting, drouth, sunscald, bruises or poor growing conditions. The trees must be kept in a healthy, vigorous condition by proper fertilization and watering. On young or transplanted trees, wrapping the trunks in early spring before the adults appear is the only effective control known for these insects. Injury can be prevented by thoroughly wrapping the entire trunk from ground level to the branches with heavy paper or other wrapping material. The wrapping should be tied securely with twine and should be maintained on the tree for 2 years. Regular observations should be made to see that the twine does not girdle the tree.
In older trees, the borers can be removed with a sharp knife. Care should be taken to injure as little of the healthy wood as possible. If the wound is extensive, it should be trimmed and then painted with a commercial tree paint or with a mixture of one part creosote and three parts coal tar. Dead and dying limbs and trees should be removed from the orchard each year and burned before the following spring. If they are not burned, the borers in them may mature and re-infest surrounding trees. Commercial tree borer preparations are of little value in controlling this insect.
OBSCURE SCALE
The obscure scale, Chrysomphalus obscurus (Comst.), is a pest of considerable importance, particularly in the more arid portions of the State. The tiny insect under its scale covering sucks the sap from the limbs and branches, causing them to lose their leaves and die back from the tips. The tree is so devitalized by the feeding of this insect that it is made vulnerable to attack by wood borers.
The scale covering over a full-grown female is about one-eighth inch long and is usually dark gray, and closely resembles the bark of the tree. Infested limbs appear to have had wood ashes sprinkled over them, [Figure 23]. Numerous pits appear in the bark where the insects feed, producing a roughened appearance.
Figure 23. Severe infestation of obscure scale on a pecan twig.