Pecan weevil can be very harmful to pecan and hickory trees, both weakening the trees and destroying the nuts. The presence of pecan weevils can be seen in a few identifiable symptom including: 1) during the mid summer, immature pecans drop to the ground and are marked with dark patches and stains; 2) late season mature nuts have small holes in them about 1/8 of an inch in size; and 3) when nuts are cut open, the kernels are often destroyed and small white worms can be seen inside.
Both the adult and juvenile pecan weevils are damaging to pecans. Adult weevils emerge from the soil in late summer and feed on immature pecan nuts, causing the under-developed pecan to drop mid-season. As the shells on the pecan nuts harden, the female weevils drill into them to lay eggs inside the nut. When the eggs hatch, the grubs feed on the kernel of the nut for a few weeks. Then, they leave the nut, drop to the ground, and burrow into the soil. The grubs then emerge as adults after two to three seasons and begin the feeding process again.
Because the grubs remain in the soil for two to three years, to be successful a control program needs to be undertaken several years in a row. In the spring, spray infected trees with Bug Buster Pyrethrin Insect Spray to help control adult feeding. Repeat spray every seven to fourteen days. When the shells begin to harden, spray every seven days with Bug Buster, until the shucks split from the shells. The weevils can also be controlled, in part, by shaking the tree and killing the weevils after they fall to the ground. To do this, place sheets or a tarp under the tree and give the tree and the branches a gentle shake, to dislodge the weevils. Repeat this process every three to five days until the weevil population declines.