The Pecan and its Culture

by H. Harold Hume

Plate X.
A Pecan Catocala. (C. Piatrix.)
Caterpillar, Cocoon, Chrysalis, and Moths about one-half natural size.

The Fall Web-Worm (Hyphantria cunea): The caterpillars of this insect begin work early in spring, shortly after the leaves are full grown. They work in colonies, and the leaves on which they feed are enclosed in a web, which is extended as the caterpillars grow or as they require additional leaves to feed upon. When full grown the caterpillars measure about one inch in length and are covered with hairs both long and short. The matured caterpillars leave the webs and crawl down the trees to hunt for places beneath the bark, under sticks, weeds and trash in which to pupate. A light, flimsy cocoon, composed of silk and the hairs of the larva, is made. From this, in due time, a beautiful moth, an inch or an inch and a quarter across the wings, emerges. The wings are pure white or white spotted with black or brownish-black. The eggs are laid in masses of four or five hundred on the leaves. These hatch in about ten days, and the colonies of young caterpillars begin their work of destruction. There are two broods in the South each summer; the first appearing in May and June, the second in August and September. The fall brood hybernates in the pupa state.

The caterpillars may be destroyed on small trees by removing the webs and killing the larvæ. On large trees a torch of some sort may be used to burn the web and the caterpillars within it. They may be also held in check by applying a spray of Paris green or arsenate of lead at the time the broods are feeding.

The Pecan Caterpillar (Datana interrigma): A buff-colored moth, having a body about one-half inch long and a wing expanse of one and three-fourths inches, with four transverse brown stripes on the front wings, lays its greenish or white eggs in clusters of five to twelve hundred on the underside of the lower leaves of the pecan trees. These eggs hatch in less than a week, and the colonies of young caterpillars at first feed upon the undersides of the leaves. They cast their skins four times, each time increasing in size and changing their color somewhat. The last moult, and sometimes the last two, take place on the trunk of the tree, and the clusters of discarded skins frequently remain for several months afterwards. After the last moult they ascend the trees, remain feeding for a short while, then go down to the ground to pupate. When disturbed, the larvæ raise both ends of their bodies from the twigs or leaves, on which they rest. They are easily recognized by this habit. When full grown they are one and one-half to one and three-quarters of an inch in length, covered with dirty white hair, and marked with two conspicuous longitudinal white lines, one on each side of the body. There are two broods, the last one hibernating in the ground in the pupa state.

The leaves on which the eggs are laid may be gathered and destroyed, or the colonies of young caterpillars may be gathered and burned. Later, they may be burned off with a torch, killed when clustered on the trunk during the last moult, or poisoned with an arsenical spray.

Insects Attacking the Trunk and Branches.

The Twig Girdler (Oneideres cingulatus and O. texana): These two insects frequently do considerable damage to pecan trees in late summer by cutting off the smaller branches. Branches from one-fourth to three-fourths of an inch are usually the ones attacked. The insect is a beetle, and the two species closely resemble each other. They are dark gray in color, one half to five-eighths inch in length, with antennæ longer than the body and provided with stout, powerful mandibles. The female insect cuts the branch by working round and round it until it is almost entirely severed. She then lays a number of eggs in it, usually one or two being placed near each bud. A small cut is made and the egg is inserted between the bark and the wood, and the opening is then sealed up with a gummy substance. As the insect moves along the twig a series of transverse cuts are made in the bark. The twigs usually drop to the ground. The eggs hatch as soon as the weather becomes sufficiently warm in spring, and the larvæ feed in the twigs, making tunnels through them as they grow. Later, they pupate within the tunnels and emerge during August and September as fully developed insects, having spent one year in their growth from egg to mature insect. It is believed that in some cases the life cycle lasts two years.

The best and most effective treatment is to gather and burn all the twigs which have been cut from the trees. This should be done, preferably late in autumn after the leaves have fallen, as there is greater certainty of getting all the severed twigs than if left until a later date.