Some time ago the statement was occasionally made that the pecan had no known enemies. This, to thinking and observing persons, was too good to be true, and fortunately the words, "no known," were inserted, for later investigations, particularly on the part of Profs. Gossard and Herrick, have revealed the fact that the pecan, in common with all other fruit trees, is subject to the attacks of insect and other enemies. But the outlook is hopeful, for we know of the abandonment of no fruit industry because of the attacks of insect pests, and the pecan industry is in no wise in danger of being abandoned because of their inroads.

Feeding Habits of Insects.

If an insect is to be successfully controlled, the grower must know something of its life-history, and particularly of its feeding-habits. Careful observation of the insect, while at its work of destruction, will frequently give a clue to the method of control. Many insects, like the caterpillars of the pecan, bud-moth and case-worm, obtain their food by biting off pieces of the leaves or other parts of the tree and swallowing the solid particles. On the other hand, a number of insects, such as the scales and plant-lice, obtain their food by thrusting their small, bristle-like sucking tubes into the tissues of the leaves and sucking out the juices contained in the cells.

It is quite obvious that these two classes of insects cannot be controlled or destroyed in the same way. Those which eat solid particles of food may, in most cases, be destroyed by applying some poisonous substance, such as arsenate of lead or Paris green, to the food which they eat. But those which obtain their food by sucking cannot be killed in this way. They can be destroyed, however, by spraying over their bodies some substance, such as kerosene emulsion, which will penetrate their bodies and so kill them. Or, they may be killed by suffocating them with a gas or by stopping up their breathing pores with some powdered substance, such as pyrethrum. Some insecticides, such as resin wash, act both as a caustic application and a suffocating covering.

For convenience in referring to insects which attack the pecan, we have grouped them as follows: (1) Insects attacking buds and leaves; (2) Insects attacking the trunk and branches; (3) Insects attacking the fruit.

The Case Worm (Acrobasis nebulella): This insect, often found associated with the bud moth, probably does more damage than any other pecan insect. The caterpillars are about five-eighths of an inch in length, a dirty brownish-green in color, and live in silk-lined cases or tubes attached to the petioles of the leaves. From these they protrude themselves to feed. Frequently a pair of leaflets are tied together (Plate IX, Fig. 6), and between these the caterpillars live and feed upon the tips of the protecting leaflets. Opening buds, partially developed and full-grown leaves alike are destroyed. Earlier in the season, characteristic nests of partially eaten leaves, petioles and excrement are formed by several caterpillars tying the mass together with silk. In this nest they live and develop. The caterpillars pupate within their silken tubes, and the small gray moths (five-eighths to three-fourths of an inch in length) emerge about two weeks after pupation, chiefly in June. The small, hibernating "cocoons" found on and around the buds in winter and the tortuous tubes observed on the leaves in summer and fall, which have been referred to (Proteopteryx deludana), probably belong to this species. At least, caterpillars one-fourth grown and contained in cocoons apparently not essentially different from the smaller ones, contain worms having the characteristic appearance of the grown acrobasis. Spraying with arsenicals in April, May and June should destroy this pest. Spraying in late July and August would also promise results of value.

The Catotocalas (Catocala piatrix and C. viduata): The caterpillars of these insects are frequently found during April, May and June feeding upon the leaves of the pecan. They are ravenous feeders, and if present in sufficient numbers, considerable damage is done. The caterpillars are from two to two and a half or three inches in length when fully extended, gray and striped, leathery in appearance, very closely resembling the back of the tree upon which they rest when not feeding. Having attained its full growth as a caterpillar, it ties together two or three leaves with strands of silk, thus making a loose cocoon within which it pupates. The pupa is dark brown, covered with a whitish or bluish-white bloom. In about one month the moths emerge. They are large in size, the body being one to one and one-fourth inches long and the expanded wings two and one-half to three inches across. When at rest they are dull gray in color, more or less marked with irregular waving lines. The hind or under-wings are strikingly different from the fore-wings. In C. piatrix they are deep orange-yellow marked from side to side with two black bands. The hind-wings of C. viduata are dark brown and edged with a narrow white band.

The caterpillars may be destroyed by spraying with some one of the arsenical poisons, or they may be removed by hand and destroyed. Prof. Gossard recommends the tying of a piece of burlap around the trees. Beneath this the caterpillars hide during the night and they may then be destroyed.

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.

The Oak Pruner (Elaphidion villosum): Sometimes[M] pecan twigs, when smartly bent, will snap off with a clean, square cut across the branches, as if they were hollow-glass tubes, breaking at cracked or weakened places. An examination of such a broken stem shows "that its woody part, with the exception of a few fibers and the bark, has been cut across as if with a saw by a soft, yellowish-white grub, which can often be found in a burrow in the severed part. Since the uncut bark is the chief support left for the branch, any stiff wind or even its own weight will break it off as soon as it has become deadened. * * * * * *

The Pecan Tree Borer (Sesia scitula): The moth of this insect is clear-winged and closely resembles the moth of the peach tree borer. Little is known of its life-history.

"It[N] is probable that the eggs are deposited by the female moth on the bark of a tree near a fresh wound. For example, near newly set buds. The eggs hatch and the larvÆ bore into the bark, and there live for a time, eating out the soft inner-bark and tender wood. It is certain that the borers live in these situations the over winter and change to pupÆ in the spring, from which the moths emerge in April. The moths I reared appeared April 3rd, 4th and 6th. The pupÆ are in cocoons, just under the bark. The cocoons are made from excrement and bits of bark that have been fastened together with silk similar to the cocoons of the peach tree borer. Whether these moths, that emerge in the spring, lay eggs and produce a brood in the summer, that in turn develops a fall brood of larvÆ, I am unable to say."

"The[O] young borer is apt to gain entrance to the sapwood through some wound in the bark, such as a graft-union, and here it feeds, sometimes completely girdling the sapwood above and below the wound. It is said to prefer to attack buds that have been budded on old, large trees. As a general rule the burrows ascend the tree in a spiral about the trunk, so complete girdling is unusual, but growth sometime ceases above the groove, new limbs being shot out from below."

The only satisfactory means of controlling this pest is to go carefully over the tree and dig out the borers. The trees should be examined from time to time in order to keep them free from borers.

Insects Attacking the Fruit.

The Pecan Weevil (Balantinus caryae): In some localities considerable damage has been caused by the pecan weevil. The insect is a small, brownish-black snout beetle, somewhat less than one-half inch in length. The proboscis or snout is slender and as long as the body. With this proboscis the beetle bores a very small hole through the husk and shell of the immature pecan to the kernel, and at the bottom deposits an egg. This egg hatches into a larva, which feeds upon the kernel of the nut. In autumn the larvÆ, when full grown, bore holes through the shells of the pecan and enter the ground in which they pass the winter. The next season they emerge from the earth as fully-matured insects, and about the month of August deposit their eggs in the nuts.

After the harvesting of the crop the hogs should be allowed to feed under trees in which the weevil is present, so as to devour any infested nuts which may have been left on the ground. Poultry may also be of assistance in destroying the insects after they have entered the ground to pupate. It is probable that the larvÆ in the nuts may be destroyed by fumigating with carbon bi-sulphide. The nuts should be placed in a tight box, and one-half pound for each five hundred cubic feet of space used, allowing them to remain for forty-eight hours.

The Hickory Shuck Worm (Grapholitha caryana): Sometimes pecan nuts are attacked, as they approach maturity, by a small, white caterpillar, which mines its way through the shucks of the nuts. This caterpillar is the hickory shuck worm, the larva of a small moth.

But little is known of its life-history, and until more is known of its habits, the best advice that can be given is to gather and destroy the infested nuts by burning them.