Part 5

Succeeding generations develop in pecan shucks. Before pupating, the larvae cut a hole to the outside, and then spin a cocoon. When the moth emerges, the empty pupal skin is left projecting from the hole and can be seen afterward on the shuck. As many as five generations may be completed each year before the last generation larvae go into hibernation.

Control.—No economical chemical control for the shuckworm has been developed. Cultural measures will aid in reducing populations. Plowing during July and August to turn under the infested shucks is relatively effective. The larvae are unable to mature in the decaying shucks, and the adults cannot emerge from the soil. Care should be taken to completely cover the fallen shucks, but the depth of plowing should be regulated or damage to the roots will result.

PECAN WEEVIL

The pecan weevil, Curculio caryae (Horn), is a late-season pest of pecans in Texas. In years when severe infestations occur, this insect may destroy a large portion of the pecan crop. The kernels are eaten out by the larvae.

The adult is a brownish weevil which is about three-eighths inch long. The female has a snout which is as long as the body; the male’s is somewhat shorter.

The weevil appears in late August and early September. After the nut kernels have hardened, the female chews a hole in the shell and deposits her eggs in little pockets in the nuts. Creamy white grubs hatch from the eggs and feed inside the nuts during the fall, attaining a length of about three-fifths inch. When they reach maturity, the grubs chew a hole about one-eighth inch in diameter in the shell, emerge from the nut and drop to the ground in late fall and early winter. They burrow in the soil to a depth of 4 to 12 inches and construct a cell. Some individuals remain in the larval stage until the following fall when pupation occurs. Other larvae do not transform to pupae until the succeeding year. The adults appear during the summer, following pupation. The entire life cycle requires from 2 to 3 years, most of this time being spent in the soil.

Control.—Frequently, certain trees in the orchard are more heavily infested than others, since the adults usually do not go far from the tree upon which they developed. The time at which insecticide applications should be made to control this insect can be determined by jarring the trees. Begin checking the first week in August. A large sheet should be placed under a tree and the limbs jarred with a padded pole. The weevils drop to the ground and remain motionless for a short period, at which time they may be counted. When three or more weevils are jarred from each tree, an application of spray containing 6 pounds of 50 percent DDT wettable powder per 100 gallons of water should be made.

STINK AND PLANT BUGS

The adults of several species of stink bugs and plant bugs suck the sap from young pecan nuts causing an injury known as black pit, in which the interior of the nuts turns black. The injured nuts fall from the trees before the shells harden.

Feeding by the insects after shell hardening, Figure 14, produces brown or black spots on the kernels. Areas affected taste bitter, but the remainder of the kernel is unaffected.

Stink bugs are familiar to everyone. Plant bugs resemble them and are usually shades of brown, smaller and narrower in body outline.

Plant bugs and stink bugs overwinter in the adult stage in debris on the ground. In the spring, the adults are attracted to growing vegetation such as cover crops or weeds, where they deposit their eggs. The immature bugs develop on low-growing vegetation. When they reach maturity, their wings are fully developed and they fly to pecan trees. A few eggs may be deposited on pecan trees, but the young bugs apparently are unable to develop on them. Only the adults are present in sufficient number to inflict economic injury. There may be as many as four generations each year.

Control.—Although certain insecticides will control these pests, the number and frequency of spray applications necessary for control would not be economical.

Care should be taken to keep weeds down in the orchard during the growing season. Winter cover crops should be plowed down early in the spring so they will not be attractive to the adults coming out of hibernation. If this operation is delayed, the bugs will leave the cover crop when it is removed and migrate to the trees in large numbers.

APHIDS

These soft-bodied insects appear during the summer and fall. They suck the sap from the leaves, causing them to turn yellow or brown and fall to the ground. Heavy infestations may cause defoliation in the late summer reducing the nut crop in the current and succeeding year.

The black pecan aphid, Melanocallis caryaefoliae (Davis), is about one-sixteenth inch long when full grown, robust and greenish black. Its back is decorated with tubercles.

Bright yellow blotches up to one-fourth inch in diameter appear around the punctures produced by the feeding of this insect.

The yellow aphids, Monellia spp., which attack pecans inflict injury similar to that caused by the black pecan aphid. However, the large yellow blotches on the leaves do not result from their feeding. A sticky substance called “honeydew” is secreted by these insects creating an ideal medium for sooty mold fungus to develop.

Both black and yellow aphids overwinter in the egg stage in crevices in the bark. In the spring the eggs hatch, and the aphids begin feeding on the leaves. Many generations are completed each year. Only females, which may be wingless or winged, are produced during the growing season. The winged individuals fly to different parts of the tree or to other trees. In the fall, males and females appear and eggs are deposited under the bark.

Usually, these insects are not present in sufficient numbers to cause serious injury until mid or late summer. Infestations earlier in the season rarely assume damaging proportions. As is the case with mites, aphid populations may increase, following the application of certain insecticides applied for the control of the pecan nut casebearer or following treatment with bordeaux mixture for pecan scab disease control.

Control.—When damaging infestations appear, the trees should be sprayed with either 1 pound of 12 percent gamma BHC wettable powder; or 1 pint of 40 percent nicotine sulfate plus 3 pounds of soap; or 1 pound of 25 percent parathion wettable powder.

MITES

These tiny pests attack the leaves usually on the underside causing irregular brown areas to appear. Trees which are heavily infested appear scorched and may lose their leaves in late summer or fall.

Mites usually are light green and are just large enough to be seen without the aid of a hand lens. They are wingless and feed principally on the underside of the leaves along the midrib. Colonies of them produce webs in which molted skins and eggs may be found. The life cycle of mites is very short and several generations occur each year. Large populations may develop during the late summer and fall.

The use of certain insecticides for the control of the pecan nut casebearer or bordeaux mixture for scab control frequently contributes to increases in mite populations later in the season.

Control.—Mites may be controlled in three ways when damaging infestations develop. An application of 2 pounds of wettable sulfur per 100 gallons of water may be made; 6 pounds of wettable sulfur per 100 gallons of water may be added to the spray applied for the control of the nut casebearer; and repeated applications of zineb included in a regular spray schedule for pecan scab control will effectively control mites. However, a single application of zineb is not effective.

PECAN LEAF CASEBEARER