Succeeding generations develop in pecan shucks. Before pupating, the larvae cut a hole to the outside, and then spin a cocoon. When the moth emerges, the empty pupal skin is left projecting from the hole and can be seen afterward on the shuck. As many as five generations may be completed each year before the last generation larvae go into hibernation.
Control.—No economical chemical control for the shuckworm has been developed. Cultural measures will aid in reducing populations. Plowing during July and August to turn under the infested shucks is relatively effective. The larvae are unable to mature in the decaying shucks, and the adults cannot emerge from the soil. Care should be taken to completely cover the fallen shucks, but the depth of plowing should be regulated or damage to the roots will result.
Figure 10. Location of overwintering cocoons, or hibernacula, of the pecan nut casebearer.
PECAN WEEVIL
The pecan weevil, Curculio caryae (Horn), is a late-season pest of pecans in Texas. In years when severe infestations occur, this insect may destroy a large portion of the pecan crop. The kernels are eaten out by the larvae.
The adult is a brownish weevil which is about three-eighths inch long. The female has a snout which is as long as the body; the male’s is somewhat shorter.
The weevil appears in late August and early September. After the nut kernels have hardened, the female chews a hole in the shell and deposits her eggs in little pockets in the nuts. Creamy white grubs hatch from the eggs and feed inside the nuts during the fall, attaining a length of about three-fifths inch. When they reach maturity, the grubs chew a hole about one-eighth inch in diameter in the shell, emerge from the nut and drop to the ground in late fall and early winter. They burrow in the soil to a depth of 4 to 12 inches and construct a cell. Some individuals remain in the larval stage until the following fall when pupation occurs. Other larvae do not transform to pupae until the succeeding year. The adults appear during the summer, following pupation. The entire life cycle requires from 2 to 3 years, most of this time being spent in the soil.
Figure 11. Overwintered larva of the pecan nut casebearer and characteristic injury to the developing shoots.