How many times have you picked up pecans only to find a small hole near the end of the shell and empty? If you grow pecans, my guess is too many. If you have experienced this damage in the previous two years, you will likely see the same damage again this year unless you take proactive measures now.
The culprit behind this damage is the pecan weevil, a beetle with a long slender snout and thin legs. They are reddish brown and about the size of a pencil eraser. The female weevil punctures the shell in mid to late August and lays an egg inside the developing nut. Once the egg hatches, the larva begin to feed on the nut and grow. This is typically the time that the nut falls off the tree and onto the ground. Once the larva has finished eating your delicious pecan, it chews a hole through the nut shell, exits, and buries itself in the soil. The larva, or grub, will then live in the soil for one to two years. To complete the life cycle, the grub will pupate and emerge from the soil as adults and begin to search for developing nuts.
To control pecan weevil larvae and adults, a good practice is to apply any liquid carbaryl product (Sevin) to the ground underneath the pecan tree out to the drip-line. Begin in mid August and make applications weekly through mid September. If you don’t feel comfortable with this many pesticide applications, you can monitor the tree for weevil populations and spray when the adults are detected. Once adult activity is detected, you can begin applications of carbaryl on the tree trunk, in the branches, and on the ground. However, this method may not provide full protection against the weevil larvae.
An easy way to monitor for pecan weevils is to tie a burlap cloth around the trunk of the trees in layers and check daily for weevil activity. You will be able to see the adult pecan weevils climbing up the burlap cloth towards the developing pecans. It is also a good practice to monitor pecans that fall from the tree and discard any with damage. This will prevent any larvae from completing their life cycle.
Remember to read and follow all labels and labeling instructions when using any pesticide. Follow all recommendations for mixing and application rates to prevent any harm to the environment. Finally, be sure to utilize all the personal protection equipment required to prevent any injury or harm to yourself.
To learn more, you can view or download the NC Cooperative Extension publication, Growing Pecans in NC, available online at http://content.ces.ncsu.edu/growing-pecans-in-north-carolina, or contact your local horticulture extension agent.
Brad Hardison is an agriculture extension agent specializing in horticulture in Sampson County.