[Illustration: Fig. 4.—Adult of a leaf-footed bug. Enlarged.]
[Illustration: Fig. 5.—Defoliation caused by the black pecan aphid.]
Nut curculios. Several species of curculios, such as the butternut curculio[9] (Fig. 2) and the hickorynut curculio,[10] infest the fruit of these and other nut trees. Their life histories and methods of attack are somewhat alike and for the purpose of this report the butternut curiculio is given as an example. This insect lays its eggs in both the young shoots and nuts, which usually drop as a result of the injury. The larvae then develop to maturity within the dying tissues after which they enter the soil and transform to adults. Subsequently they leave the soil to pass the winter above ground protected from low temperatures by weeds or other vegetation.
[9] ~Conotrachelus juglandis~ Lee.
[10] ~Conotrachelus affinis~ Boh.
Lead arsenate, 4 pounds per 100 gallons of water, has been relied upon in the past for control of various nut curculios. Among the newer insecticides, benzene hexachloride (6 percent gamma), 4 to 6 pounds per 100 gallons, has shown promise against a shoot curculio on pecans when applied soon after the trees start growth in the spring.
~Hickory shuckworm.~ The hickory shuckworm[11] is another serious pest of pecan and hickory nuts. Early in the year, previous to the hardening of the shells, the kernels are eaten. This injury causes many of the nuts to drop. In the fall, the later generations tunnel within and feed upon the shucks only. The affected nuts are usually smaller than normal; in addition the shells are often stained and are more difficult to separate from the husks.
[11] ~Laspeyresia caryana~ (Fitch).
Extensive experimentation in the control of this insect has been carried out without much success. No effective insecticide treatment can be recommended for its control.
~Walnut husk maggot.~ The adult of the walnut husk maggot[12] is a fly (Fig. 3); it is related to other injurious fruit flies such as the apple maggot, Mediterranean fruit fly, and the oriental fruit fly, which has recently been found in Hawaii. Adults emerge from the soil and fly to the trees in midsummer. Egg laying follows in 1 to 3 weeks, the eggs being deposited on the husks of several kinds of nuts. The maggots feed within the husks. Not only is the quality of infested nuts lowered, but, in addition, the husks are more difficult to remove. A closely related species is particularly damaging to the Persian or English walnut in California.