The Pecan and its Culture Part 14

Slack the lime, reduce it to a very thin paste, place it in barrel No. 2 and add water to make twenty-five gallons. To mix the solutions of lime and copper sulphate, dip a bucketful from each barrel, and pour together into the barrel of the spray pump. _The two mixtures should flow together as they are poured into the barrel._ This is one of the secrets of making a first-cla.s.s mixture. The best arrangement is to have the barrels, Nos. 1 and 2, elevated, and use a piece of rubber hose to run the liquids into the pump barrel.

If a large amount of spraying is to be done, a somewhat different policy should be pursued. Too much time would be taken up in preparing the ingredients in small quant.i.ties.

Instead, large amounts of copper sulphate should be dissolved and large quant.i.ties of lime slacked beforehand. This may be done as follows:

In a fifty-gallon barrel place about forty gallons of water.

Put one hundred pounds of copper sulphate in a sack and suspend it in the water. As soon as dissolved, fill up to the fifty-gallon mark. When well stirred, each gallon will contain two pounds of copper sulphate. Each time some of the solution is dipped out, the height of the remaining portion should be marked on the inside of the barrel. Before taking more of the solution out of the barrel, any amount of water lost by evaporation should be made good by filling up to the mark last made.

As soon as procured the lime should be slacked, placed in a barrel and kept covered with an inch or two of water. In this way it can be kept indefinitely.

To prepare Bordeaux mixture from these stock solutions, dip out two and a half gallons of the copper sulphate solution, place it in barrel No. 1 and dilute to twenty-five gallons. From the slacked lime take fifteen pounds, or thereabouts, to allow for the water it contains, reduce to a thin paste, place it in barrel No. 2 and add water to make twenty-five gallons. Pour the contents of barrels Nos. 1 and 2 together, as already directed.

_Tests_: If free copper be present, severe injury may be done to the foliage or other tender parts of the plants. Sufficient lime should be added to neutralize it.

Dip out a small quant.i.ty in a porcelain saucer or shallow bowl, and holding it on a level with the mouth, blow the breath gently into it. If a thin pellicle forms on the surface, more lime must be added. Add and test until it does not form. An excess of lime will not hurt.

Another test is to dip the blade of a clean knife into the mixture. If a thin film of copper forms on it after holding it there a minute or so, more lime must be added.

Use good materials and prepare the mixtures thoroughly.

In making up the various mixtures, never use iron vessels, but use gla.s.s, wood or crockery receptacles instead.

Strain all mixtures thoroughly into the spray pump to prevent clogging of the pump or nozzles.

Spray thoroughly and in good season. _Be in time._

Do not use mixtures which have been leftover and allowed to stand for some time.

FOOTNOTES:

[L] Orton, W. A., proceedings second annual convention National Nut Growers' a.s.sociation, 1903, p. 82. 1904.

CHAPTER XV.

INSECTS ATTACKING THE PECAN.

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.

[Ill.u.s.tration: PLATE VIII. The Pecan Bud Moth (Proteopteryx deludana).

1. Winter stage on bud, enlarged. 2. Tube made in leaf. 3. Work of bud destruction. 4. Caterpillar, enlarged about twice. 5. Coc.o.o.n, enlarged.

6. Chrysalis, reduced. 7. Moth, enlarged. 8. Moth, about natural size.]

It is quite obvious that these two cla.s.ses 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 a.r.s.enate 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.

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 circ.u.mstantial 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 pupae 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 a.r.s.enate of lead or Paris green, in April and May, ought to control this species."

THE CASE WORM (_Acrobasis nebulella_): This insect, often found a.s.sociated 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 ma.s.s 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 "coc.o.o.ns" 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 coc.o.o.ns apparently not essentially different from the smaller ones, contain worms having the characteristic appearance of the grown _acrobasis_. Spraying with a.r.s.enicals in April, May and June should destroy this pest. Spraying in late July and August would also promise results of value.

[Ill.u.s.tration: 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 coc.o.o.n 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 a.r.s.enical 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.

[Ill.u.s.tration: PLATE X. A Pecan Catocala. (C. Piatrix.)

Caterpillar, Coc.o.o.n, 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 coc.o.o.n, 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 ma.s.ses 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 larvae. 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 a.r.s.enate 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 cl.u.s.ters 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 cl.u.s.ters 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 larvae 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 cl.u.s.tered on the trunk during the last moult, or poisoned with an a.r.s.enical 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 antennae 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 larvae 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.