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.
[Illustration: 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
[Illustration: 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.