The obscure scale and other scale insects can be controlled with lubricating-oil emulsion during the dormant period. However, nut trees are often susceptible to oil damage, especially at 3 percent concentration. Since healthy trees are more resistant to oil injury, it is therefore advisable to watch for scale infestations so as to spray them before the trees are weakened.
~Twig girdler.~ Nut trees are sometimes attacked by the twig girdler[24] (Fig. 11). This beetle lays eggs in the twigs, which are girdled so as to stop the flow of sap that would normally prevent hatching. The girdled twigs usually become detached from the trees and as a result the nut-bearing wood is reduced.
[24] ~Oncideres cingulata~ (Say).
The standard recommendation for control of this insect has been to gather and destroy the infested twigs in the orchard and from any infested trees nearby. Recent tests on pecan in northern Florida indicate that DDT and parathion may be effective against this insect. Three applications (the first on August 26 when the first girdled twigs were observed and the others on September 9 and 23) of DDT, 4 pounds of 50 percent wettable powder per 100 gallons of water, or parathion, 3 pounds of 15 percent wettable powder per 100 gallons, gave complete control. Further experiments will be required to determine the minimum effective concentration of spray and the number of applications needed for control. It is suggested that DDT be used for the control of this insect until more information is available on how to handle and to use parathion.
~Flatheaded apple tree borer.~ The adult beetle of the flathead apple tree borer[25] (Fig. 12) deposits its eggs throughout the summer season, preferably in the small grooves of bark on the unshaded portions of the trunk of pecan and other trees. The borers (Fig. 13) hatch and tunnel through the bark to the cambium layer. Young trees may readily be girdled (Fig. 14).
[25] ~Chrysobothris femorata~ (Oliv.).
To avoid this insect as far as possible, orchard sanitation should be practiced and the trees should be kept in a healthy condition. In some plantings wrapping the trunks with paper or burlap to protect against egg laying and maintaining low branches to shade the trunk have been helpful. Cutting out the borers with a knife has also been resorted to; trunk washes have likewise been used but have not been very effective.
~Buffalo treehopper and periodical cicada.~ Buffalo treehoppers[26] (Fig. 15) and the periodical cicada[27] weaken twigs by inserting their eggs in them. The injured bark becomes roughened as it heals (Fig. 16), and the growth of the limb is retarded.
[26] ~Ceresa bubalus~ (L.).
[27] ~Magicicada septendecim~ (L.).