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.
Insects Attacking Buds and Leaves.
The Bud Worms: At least two species of caterpillars are known by this name. The moth of one has been called the bud-moth. The caterpillar of the other has been called the case-worm. Prof. Gossard writes, that he unexpectedly found adult moths of Proteopteryx deludana, November 28th, 1905, and therefore believes, from this observation and other circumstantial evidence, that he was "mixed" regarding the autumn life-history of these insects, as set forth in Bulletin 79 of the Florida Experiment Station. He furnishes the following paragraph as a summary of what he can say of the bud worms:
"The Bud Moth, Proteopteryx deludana, is a serious pest, especially in young orchards. Sometimes, in such orchards, even when large, scarcely a tree can be found during the month of May that does not contain one or several nests. The caterpillars are usually found singly, each with one side of a leaf folded over it and fastened to form a tube, or sometimes two leaves are fastened together with silken bonds and the caterpillar feeds between them. As fast as the leaves it has attached become brown and die, it draws fresh leaves to the dead ones and fastens them there, thus gradually making a very conspicuous nest. The caterpillar is full grown during the last of May and the first of June when they transform into moths. Their pupæ cases are formed of silk and excrement, smoothly lined with silk and snugly hidden away in a nest of leaves. In about two weeks from the time of pupation, the moths appear. Early specimens have sometimes been hatched from buds, only partially expanded. They are small, about five-sixteenths of an inch in length and five-eighths of an inch across the expanded wings. In general color they are grayish, streaked and dotted with blackish-brown. A characteristic habit is to alight and rest on the tree trunk, head downward. The moths have again been observed in November, suggesting that there are two broods a year. Thorough, persistent spraying with arsenate of lead or Paris green, in April and May, ought to control this species."
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.
Plate IX.
The Case Worm.
1. Supposed winter stage. 2. Caterpillar, enlarged. 3-4. Moth, nearly natural size. 5. Cases. 6. Work on leaves.
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.