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.
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
[1]Bilsing, S. W., 1916; Life history of the pecan twig girdler. Journal Econ. Ent. 9:110-115.
[2]Bilsing, S. W., 1927; Studies on the biology of the pecan nut casebearer. Texas Agricultural Experiment Station Bulletin 347, 71 pp.
[3]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.
[4]Dobbins, Traber Norman, 1932; The biology of the pecan phylloxera. Master’s Degree Thesis, Texas A. and M. College.
[5]Dorman, Harvey S., 1934; The life history of the yellow pecan aphid Monellia nigropunctata Granovsky. Master’s Degree Thesis. Texas A. and M. College.
[6]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.
[7]King, D. R. and David W. Rosberg, 1956; Control of Tetranychus hicoriae McG. on pecans. Journal Econ. Ent. 49 (3):404-5.
[8]Nickels, C. B., 1952; Control of the pecan weevil in Texas. Journal Econ. Ent. 45 (6): 1099-1100.
[9]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.
[10]Rosberg, David W., 1950; Control of pecan diseases in 1950. Texas Agricultural Experiment Station Progress Report 1330.
[11]Rosberg, David W. and D. R. King, 1954; Pecan disease and insect control experiments in Texas, 1953. Texas Agricultural Experiment Station Progress Report 1671.
Your County EXTENSION AGENTS
can furnish you the latest information on farming, ranching and homemaking. They represent both The Texas A. & M. College System and the United States Department of Agriculture in your county.
Most county extension agents have their offices in the county courthouse or agriculture building. They welcome your visits, calls or letters for assistance.
This publication is one of many prepared by the Texas Agricultural Extension Service to present up-to-date, authoritative information, based on results of research. Extension publications are available from your local agents or from the Agricultural Information Office, College Station, Texas.
Cooperative Extension Work in Agriculture and Home Economics. The Texas A. & M. College System and United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, and June 30, 1914.
10M-3-59. Reprint.