Pecan showing signs of pecan weevils. (Photo contributed) Have you ever thought you were going to have a bumper crop of pecans, only to have empty shells? This could be caused by low fertility, dry weather, or pecan weevils. Chances are you have pecan weevil damage. Pecan weevil can easily be identified as a small hole on the side of the shell, with no meat inside. Pecan weevils usually do not infest one or two, but usually wreak-havoc on the entire crop.

Pecan weevil larvae (caterpillar stage) live in earthen cells in the soil. In early September, the larvae pupate into adults, in which they emerge when soil becomes soft due to harrowing or wet conditions. In drought conditions, emergence maybe slowed due to soil compaction. Weevils emerge from the soil in the adult form, where both sexes will begin feeding on pecans. After the shells become hardened and kernel formation begins, the female chews a hole through the shell and deposits eggs inside the nuts. The eggs (usually 3 to 5 per pecan) and larvae that develop from them remain in the nuts for about a month. Upon completion of development, larvae chew“exit” holes in the pecans and drop to the soil. This occurs primarily during October and November but can extend into December. Many times larvae will leave the nuts while the pecans are still on the trees. In these instances, the “exit” holes will be evident through the green shucks, and these weevil-damaged pecans will tend to hang on the trees longer than normal. The larvae from infested pecans will then return to the soil, and live there until the following year.

The pecan weevil causes two types of direct damage to pecans. Prior to shell hardening, feeding punctures by adults cause immature pecans to fall from the trees.

The second type of damage occurs later in the season. After the shell hardens and the kernel begins to form, females lay eggs in the pecan. The grubs that hatch from these eggs destroy the kernel by their feeding. This damage shows up at harvest either as wormy pecans or hollowed out nuts with larval emergence holes present.

Control

As someone who owns a few trees in the back yard, or someone that has 100 acres, control can be obtained. As a homeowner, the best level of control is spraying the base of the tree with a 10% application of Sevin. As weevils emerge from the ground, they must come into contact with the trunk to make their way to the rest of the tree. Sevin tends to hang around a while, and again provides the best level of control. A homeowner can spray low hanging limbs with Sevin, as this will prevent weevils from jumping from the ground to these limbs. All of this can be obtained with a hand sprayer.

Pecan weevils cause the most economic damage to pecans than any other insect. However, from a commercial and homeowner stand point, they can be controlled. I have heard people time and time again complain about weevil damage to their back yard pecans! In a few weeks, you will have a chance to redeem yourself from weevil damage.