Prior to shell hardening, the presence of a larva in the nut indicates damage by some other insect, usually nut curculio or hickory shuckworm. Pecan weevil grubs are not found in nuts with unhardened shells. Early feeding damage by adult weevils can be serious if the nut crop is light. After pecan shells harden, female weevils drill holes through the shucks and hardened shells and place an average of about 3 eggs each in separate pockets within the kernels. Grubs hatch and feed on the kernels, destroying the interior of the nut.
Trees growing in low areas and near hickory trees are more likely to be infested.
Certain trees may be infested year after year, while nearby trees, even of the same variety, may be almost weevil free. Trees with history of infestation should be checked when sampling for weevils. Weevil emergence is dependent upon soil moisture and is usually higher following rains. Adult pecan weevils emerge from the soil from July to October with most emergence from August 1 through September 20. They construct earthen cells where they remain for 1 - 2 years.