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.
Control.—Frequently, certain trees in the orchard are more heavily infested than others, since the adults usually do not go far from the tree upon which they developed. The time at which insecticide applications should be made to control this insect can be determined by jarring the trees. Begin checking the first week in August. A large sheet should be placed under a tree and the limbs jarred with a padded pole. The weevils drop to the ground and remain motionless for a short period, at which time they may be counted. When three or more weevils are jarred from each tree, an application of spray containing 6 pounds of 50 percent DDT wettable powder per 100 gallons of water should be made[8].
Figure 12. Eggs of the first generation pecan nut casebearer deposited on the tips of the young nuts.