This time of year our thoughts usually turn to the sights, tastes, and aromas of autumn, such as the beautiful fall foliage and pumpkin pie or sweet potato pudding. I fondly remember my mother’s sweet potato bread, warm from the oven and absolutely delicious. It had to have chopped pecans to be complete. She would prepare it sometimes without pecans, but it just didn’t taste the same.
Speaking of pecans, I know many folks will soon be harvesting the valuable nut or just picking them up in the smaller yard setting. As we begin our search for the perfect pecans, we will see many imperfect or diseased pecans. Pecan trees are subject to attack by more than 20 insects and mites. However, only four insects — the pecan weevil, twig girdler, stink bug, and aphids — are usually of economic importance in North Carolina.
The pecan weevils’ damage may be most easily recognized. The full-sized shell will feel lighter and have a very obvious bb-sized hole where the developing larvae will exit the shell and enter the ground to mature into the adult weevil. The adults emerge during August and September of the following year to repeat the cycle. Collecting the infected nuts as soon as possible prevents the larvae from entering the ground. Spraying the ground, starting early August, with four to five applications every 10 to 14 days will reduce the emerging population. The carbaryl application should be surface applied from the trunk to the drip line of the tree. Always follow the directions on the label of any pesticide — the label is the law.
Twig girdler pressure can be reduced with simple sanitation by keeping the broken twigs and branches picked up as soon as they fall and burning them. This will kill the eggs and larvae present. Twig girdlers girdle the tips of small pencil-size branches in September, laying their eggs in the hewn out area of the branch. Larvae feed on the damaged branch until wind causes the weakened branch to fall to the ground. This larva also exits the twig to enter the ground to mature.
Stink bugs are very mobile, making them hard to control, but their damage can be early nut drop when they puncture the nut to feed before shell hardening. They can also feed after shell hardening, causing black spots to develop on the nut kernel. These spots are bitter. Stink bugs overwinter in debris and vegetation in the orchard or yard. Sanitation will reduce stink bug populations.
Aphids feed on the leaves of pecan trees, leaving honeydew, a sweet excrement, on the leaves. A black, sooty mold fungus develops on the honeydew ,turning the surface of the leaves black. Heavily infected trees can exhibit early leaf fall. Aphids are usually held in check by natural predators. Pesticides should be the last resort. The common element in reducing these pest populations is also the simplest — sanitation. Remember, keeping leaves, nuts, and branches picked up and off the ground will result in a more edible harvest for you.
Mack Johnson is an Extension horticultural agent with North Carolina Cooperative Extension, Robeson County Center. He can be reached at 910-671-3276 or by email at Mack_Johnson@ncsu.edu.