Major Insect Pests

Pecan weevil

Pecan weevil damage to pecan nuts.

Adult weevils feed on young pecan nuts. This feeding injury may cause the nut to drop. Later in the season, eggs are laid in the husks of both pecan and hickory nuts. The eggs hatch into legless grubs, which bore into the nut and eat the kernel. Because the pecan weevil overwinters in the ground, sanitation is not an effective control against this pest, sprays must be applied every 2 to 3 weeks throughout the summer.

To be effective against this pest, sprays must be applied every 2 to 3 weeks throughout the summer.

Hickory shuckworm

Hickory shuckworm in young pecan nut. After the shell hardens, later generations of shuckworms work in the husk.

The adult stage of this insect is a moth that lays eggs on or near pecan and hickory nuts. The eggs hatch into caterpillars that feed on the nut or husks. During the growing season more than 1 generation may develop. Before the shell hardens, the caterpillars enter the nut and feed on the young kernel, thus causing the nut to drop. After the shell hardens, the caterpillars bore into the husks (see image). This feeding interferes with normal nut filling and causes black stains on the shell.

The hickory shuckworm overwinters in the husks on the ground. Sanitation will help control this pest in small, isolated plantings. Each fall or early spring, rake up and burn or haul away all husks. During the growing season, burn or haul away any immature nuts that fall.

Walnut huskfly maggot

The maggot overwinters in the ground and emerges in mid- to late summer as a fly. The adult fly lays eggs in the husks of black and Persian walnuts.

The eggs hatch into small legless maggots that feed on the husks. Feeding damage stains the shell and may cause discolored and off-flavored kernels.

Damage usually is more severe on Persian walnuts than on black walnuts. Sprays of carbaryl (Sevin), malathion, or carbaryl and malathion should be applied every 2 to 3 weeks during July and August for control.

Pecan nut casebearer

These insects overwinter as caterpillars enclosed in cocoons attached to the twigs of pecan, hickory, black walnut, and Persian walnut. At bud break in spring, the caterpillars emerge and feed on the buds, then bore into the new shoots. After feeding for a short time, they pupate and change into moths. The moths start egglaying about the time the new nuts start to form. The eggs hatch into caterpillars that feed on the new nuts, destroying them. In Illinois there are usually 1 or 2 succeeding generations that feed on the leaves and shucks.

Injury is more severe on pecans. Control with a spray of carbaryl (Sevin) when the tips of the young nuts turn brown.

Foliage-eating caterpillars and worms

Fall webworms, walnut Datana, eastern tent caterpillars, hickory tussock moths, walnut caterpillars, and other leaf-eating caterpillars and worms frequently attack nut trees. When infestations occur, control with carbaryl (Sevin) or Bacillus thuringensis (many).

Plant bugs, stinkbugs, and spittlebugs

These juice-sucking insects damage the nuts. Feeding on young nuts may cause the nuts to drop or may cause part or all of the kernel to turn brown and shrivel (see figures below).

These pests are general feeders and attack a wide variety of plants, moving about rapidly. They are more prevalent in areas where tall grass and weeds are growing. Keep the nut grove mowed.

Spittlelike substance produced by spittlebugs on young pecan nuts.

Discolored, bitter spots on pecan kernels caused by stinkbug feeding.

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