Nut weevils cause a lot of damage to hickory and other nut trees when they attack the kernels developing in the nuts that are growing on the trees. Commercial growers can use insecticides to help control weevil problems, but insecticides are too expensive for most backyard growers. To sort weevil-infested nuts from edible ones, put the hickory nuts in water. Edible nuts will sink. Floating nuts should be thrown away because they don't contain good kernels.
Hickory shuckworms are the caterpillars of a moth that lays eggs on and near hickory and pecan nuts. The caterpillars are white with a reddish-brown head and grow to be between 1/3 and 1/2 inch long. After the caterpillars hatch, they eat the nuts and husks, then enter the nut before the shell hardens, and eat the kernel inside. This feeding causes the nuts to drop from the tree prematurely. Symptoms of shuckworm damage include the appearance of black stains on the shell, scarring on the shell and poor kernel development.Hickory shuckworms overwinter in nut husks on the ground.
Rake up all nut husks in the fall or spring and burn them. Burn or remove immature nuts that fall off the tree during the growing season. Shuckworms can also be controlled with several applications of insecticidal spray. The pH of the water being used for spraying should be between 5.5 and 6.5 for maximum efficiency.
Pecan weevil larvae are creamy white grubs that grow to be about 3/5 inch long. They have reddish-brown heads and no legs. The adult beetles lay their eggs in the husks of pecan and hickory nuts, and the grubs that hatch from the eggs bore into the nuts and feed on the kernel from late summer through the fall. At that point, they chew their way out of the shell and fall to the ground where they spend the winter in cells about 4 to 12 inches under the soil. Adult beetles, which are reddish-brown with thick olive-brown hairs, grow to be about 3/8 inch long and damage hickory nuts by feeding on the nuts and causing them to drop prematurely. Grubs also cause damage to the nut kernels by feeding on them.
Trees should be monitored for the presence of adult weevils and, when three or more adults are found per tree, they should be sprayed with an insecticidal spray every two to three weeks during the summer. Raking and removing nut husks won't control this pest because pecan weevils overwinter in the ground.
- Illinois College of Agricultural, Consumer, and Environmental Sciences: Major Insect Pests
- Tulsa Master Gardeners: Hickory Shuckworm
- Texas Agrilife Extension: Pecan Weevil
- LSU AgCenter; Hickory Shuckworm; Michael J. Hall
- University of Kentucky College of Agriculture; Nut Weevils; Ric Bessin
- Iowa State University; Wormy Acorns and Hickory Nuts; Donald Lewis; October 2008