Pecan Insect and Disease Control
Phylloxera is an aphid-like insect that causes tumor-like galls or growths on the stems and leafstalks of pecan trees. These growths usually are large enough to be noticed by late May or early June. If infestations of these insects are moderate to high, pecan production will be severely cut, and successive, yearly infestations will reduce the life of the tree. The only control is an insecticide application, and the timing of this application is very important. Apply the insecticide at or shortly after bud break. If new stem growth reaches one inch in length or longer without an insecticide application, some damage may have occurred.
May Beetles May beetles are brown beetles that feed on leaves at night in May and June. Pecan Weevils Pecan weevils are light brown or grayish beetles about 1/2 inch in length with long beaks. The weevil is called a grub in its young stage and spends its time inside the nut feeding on the kernel. When the grub comes out to enter the soil, it leaves a 1/8-inch-round hole in the nut. The time the adults emerge from the soil may vary, but it usually occurs in late July or early August and lasts into September. Egg laying will start with shell hardening. Begin control measures when emergence has occurred and the shell begins to harden. Apply a minimum of four applications one week apart. Walnut Caterpillars Walnut caterpillars are black with long, soft hairs. They feed in colonies on leaves. Fall Webworms Fall webworms are hairy, pale-yellow caterpillars up to 1 1/4 inches long that feed on leaves in large, white webs during summer. Yellow Pecan Aphids Yellow pecan aphids are soft-bodied, yellow to green sucking insects that occur on the underside of leaves. They produce and secrete honeydew from their bodies. The honeydew drips onto the leaves below, giving them a shiny appearance. Leaves later become blackened by sooty mold. Black Pecan Aphids Black pecan aphids are small, black, sucking insects. They cause bright-yellow spots on leaves that later turn brown, and they cause leaves to shed. They may cause severe damage and shedding of leaves from July to September. Twig Girdlers Twig girdlers are very destructive to young trees. They lay eggs on twigs and branches that become girdled and fall from the trees. Other Pests Other pests of pecans include pecan nut casebearers, leaf casebearers, spider mites, obscure scale, shuck worm, and spittle bugs.
Scab Disease Scab disease is a fungus that causes damage on susceptible varieties, especially during rainy seasons. Pecan varieties most seriously affected include Schley, Mahan, Success, Van Deeman, and Stuart. The fungus lives through the winter on leaves, shucks, and twigs. The disease attacks the young leaves then spreads to the small nuts. Black, sunken spots on the leaves and the nuts may become so numerous the entire surface is covered. Severe leaf and nut infections cause shedding of both.
Leaf Spot Disease Leaf spot diseases are caused by several different fungi that cause leaves to shed.
Sanitation or Destruction
Sanitation or destruction of leaves, shucks, and faulty nuts under trees each winter will help reduce damage from scab and leaf spot diseases, shuck worm, and other pests.