Part 8

The adult beetle is about one-half inch long, broad and blunt at the head end and tapering to a point posteriorly. Its wing covers, which have a metallic sheen, are dark colored and corrugated.

The larva, or borer, which is legless and yellowish white, attains a length of 1¼ inches when full grown. Immediately behind the head is a broad, flattened expanded area from which the insect takes its name.

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.

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.

The winter is passed by the female scales under their coverings on the bark. Eggs laid in the spring hatch into tiny, salmon-colored crawlers which move about for a short time, then settle down and insert their beaks. While they are feeding, a scale covering develops which is made up of secreted wax and cast skins.

The females never move again from the spot they have selected, but the adult males develop wings and emerge from their scale coverings to mate with the females. Only one generation is produced each year.

Control.—When damaging populations develop, a spray application of 3½ gallons of 97 percent miscible dormant oil per 100 gallons of water during the dormant season will keep this pest under control.

Application of Fungicides and Insecticides

When possible, fungicides for disease control and insecticides for insect control should be combined in the spray tank and applied to the trees in one operation. The spray materials should be applied evenly and thoroughly to all the leaf and nut surfaces to provide a chemical barrier to disease organisms and insects. Do not neglect the tops of the trees. Diseases and insects can harbor and multiply in all unsprayed areas of the tree.

Thorough coverage with spray materials is essential for effective control. As a guideline, apply approximately 1 gallon of spray mixture for each foot of tree height. Apply 20 gallons to a 20-foot tree and 40 gallons to a 40-foot tree, etc.

Spray Equipment

Various types of spray machines for application of fungicides and insecticides to pecan trees are available. The spray machines employ either a high pressure hydraulic pump, high pressure centrifugal pump or low pressure high air velocity systems. All the machines are portable and are equipped with a gasoline engine or operate from a truck or tractor power takeoff shaft.

For pecan spraying, a tank having a minimum capacity of 300 gallons is desirable. The pump should deliver 20 to 30 gallons per minute and maintain a pressure of 400 to 600 pounds per square inch while operating. A spray gun which is adjustable to produce a mist spray for spraying small trees or the lower canopy of large trees and a narrow stream that will reach the tops of tall trees is essential.

For safety and durability high pressure rubber hose having an inside diameter of three-fourths inch should be used with all high pressure spray machines.

Literature Cited

Bilsing, S. W., 1916; Life history of the pecan twig girdler. Journal Econ. Ent. 9:110-115.

Bilsing, S. W., 1927; Studies on the biology of the pecan nut casebearer. Texas Agricultural Experiment Station Bulletin 347, 71 pp.

Bilsing, S. W., 1941; An economical method of removing Spanish moss (Tillandsia usenoides) and Ball moss (Tillandsia recurvata) from trees. Texas Agricultural Experiment Station Progress Report 747.

Dobbins, Traber Norman, 1932; The biology of the pecan phylloxera. Master’s Degree Thesis, Texas A. and M. College.

Dorman, Harvey S., 1934; The life history of the yellow pecan aphid Monellia nigropunctata Granovsky. Master’s Degree Thesis. Texas A. and M. College.

King, D. R. and David W. Rosberg, 1955; Experiments for the control of pecan insects and diseases, 1954. Texas Agricultural Experiment Station Progress Report 1786.

King, D. R. and David W. Rosberg, 1956; Control of Tetranychus hicoriae McG. on pecans. Journal Econ. Ent. 49 (3):404-5.

Nickels, C. B., 1952; Control of the pecan weevil in Texas. Journal Econ. Ent. 45 (6): 1099-1100.

Osburn, M. R., A. M. Phillips, William C. Pierce, and John R. Cole, 1954; Insects and diseases of the pecan and their control. USDA Farmers Bulletin 1829, 56 pp.