Part 7

Control.—Light infestations on a few trees can be eliminated by pruning out the affected branches and burning them. If this method of control is not practicable, the trees should be sprayed with 2 pounds of 50 percent DDT wettable powder; 1 pound of 25 percent parathion wettable powder; or 3 pounds of lead arsenate per 100 gallons of water.

WALNUT CATERPILLAR

During the spring and summer, the walnut caterpillars, Datana integerrima G. & R. and others, may strip the leaves from branches or entire small trees. The adult is a moth with a wingspan of 1½ to 2 inches. The forewings are light brown with darker wavy lines. The hindwings are lighter in color without lines.

The immature larva is reddish brown with narrow yellowish lines that extend the length of the body. The full-grown larva is almost black with two grayish lines on the back and two on the sides. Many long, soft gray hairs are distributed over the body.

This insect overwinters in the pupal stage in the soil. The adult emerges in the spring and deposits eggs in masses on the underside of the leaves, Figure 20. The larvae feed in colonies on the leaves for about 3 weeks. At periodic intervals, the groups of larvae move to the trunk to molt and, after shedding their skins, they return to the leaves to feed until the next molt. They do not encase themselves in webs. There are two generations each year, the first appearing in late spring and early summer, the second in later summer and fall. Larvae of the second generation complete development and crawl down to pupate in the soil.

Control.—When these insects become abundant enough to defoliate portions of the tree, they may be controlled by applying a spray containing 2 pounds of 50 percent DDT wettable powder; 3 pounds of lead arsenate; or 1 pound of 25 percent parathion wettable powder per 100 gallons of water.

PECAN CATOCALA

Several species of catocalas, Figure 21, among them Catocala maestosa Hlst., may strip the leaves of pecans in the spring leaving only the midribs. The caterpillars are very dark gray and attain a length of about 3 inches when full grown. They are very active when disturbed and move with a looping motion. Both the caterpillars and the moths are well camouflaged. When they rest on the trees during the day, their color so harmonizes with the color of the bark that they are frequently indistinguishable.

Control.—One application of 2 pounds of 50 percent DDT wettable powder per 100 gallons of water controls this pest. Although the majority of catocala larvae reach maturity before the time to spray for the nut casebearer, a number of them will be killed when the recommended spray is applied for the latter insect.

PECAN SPITTLEBUG

In the spring and early summer a number of buds and small nuts may be covered with foamy white masses. Inside these masses are several small insects called spittlebugs, Clastoptera obtusa (Say). The white froth is produced probably to maintain an artificial high humidity, which is required for development. The adults resemble leafhoppers and fly actively during the summer.

This insect has not been known to cause any significant injury on pecans in Texas.

PECAN BUD MOTH

The pecan bud moth, Gretchena bolliana (Sling.), damages nursery stock and freshly top-worked pecans. The greenish larvae feed in the axils of the newly set buds and in the terminals of young trees, causing extensive branching. There are several generations each year.

Control.—This insect may be controlled by applying a spray containing 2 pounds of 50 percent DDT wettable powder per 100 gallons of water.

TWIG GIRDLER

The adult twig girdler, Oncideres cingulata (Say) (O. texana of some authors), girdles twigs and branches, weakening them so that they fall off or die on the tree, Figure 22. This insect is active during the late summer and early fall. Many twigs may be found on the ground under a severely infested tree. Secondary branching may occur and the number of bearing twigs is reduced.

The twig borer is a grayish brown beetle one-half to five-eighths inch in length with a broad gray band over the middle of the wing covers. Its head is reddish brown and bears a pair of long antennae, which extend beyond the abdomen on the male.

The larva is a white legless grub about three-fourths inch long when it reaches maturity.

This insect overwinters as a partially grown larva in a twig on the tree or ground. It develops rapidly in the spring feeding in the twig. Following pupation, the adult emerges in late August or early September. The female systematically girdles twigs and deposits eggs in the severed portion since the larva is unable to develop in healthy sapwood. The eggs hatch in a few weeks into larvae which remain small until the following spring when they complete development, pupate and emerge as adults in the late summer and fall. There is one generation annually, although some individuals require 2 years to mature.

Control.—Infestations may be reduced by removing girdled branches from the trees and the ground and burning them.

Chemical control is also effective. The trees should be sprayed with 4 pounds of 50 percent DDT wettable powder per 100 gallons of water when the first injured branches are observed in late August or early September. Two or three applications at 2-week intervals may be required for most effective control.

RED-SHOULDERED SHOT-HOLE BORER

The red-shouldered shot-hole borer, Xylobiops basilare (Say), and other shot-hole borers also injure trees in a devitalized condition. The larvae feed in wood, pupate and emerge as adults through round holes about one-eighth inch in diameter in the bark. Many of these holes may be observed in close proximity to each other.

Control.—Since this insect feeds on dying or dead wood, prunings and dead limbs should be removed from the orchard and burned.

Adequate fertilizer and water will keep trees in a healthy condition and prevent injury by this pest.

FLATHEADED BORERS

The flatheaded apple tree borer, Chrysobothris femorata (Oliv.), and other species of flatheaded borers attack unhealthy or recently transplanted pecan trees by burrowing in the bark and sapwood of the large branches and trunk. Their presence is indicated by the appearance of darkened, depressed areas in the bark from which traces of frass may protrude. When these portions of the bark are removed, shallow winding burrows packed with sawdust may be observed. The burrows usually are on the sunny side of the trunk or branch, but may extend completely around and penetrate the wood to a depth of 2 inches. Young trees may be girdled by this insect.