Chapter 3 COTTON-PLANT DISEASES AND PESTS.

There are several classes of agents all of which act injuriously more or less on the Cotton plant.

1. Climatic changes, including hygrometric variations of the atmosphere, and extremes of heat and cold.

2. Insect pests.

3. Physiological diseases of the plant.

4. Blights caused by fungi.

It has been pointed out in the early pages of this story, how very sensible to changes of heat and cold, the Cotton plant is, especially in the early growing period. When the plant has just risen above the ground, and is beginning to spread its roots, too great an amount of heat would be fatal to its further growth.

Instances could be given where very serious decreases in the production of cotton in the States especially have taken place, due entirely to unusually high temperatures which obtained during the early growing period of the Cotton plant.

Extremes of frost are likewise fatal to the growth of the young plant. By the beginning of April, frosts have as a rule disappeared, and no further fear need be felt on that account, though if the end of winter has been abnormally warm, and the young plants have been making leaf too quickly, it will be readily seen how fatal a sharp frost or two must be to the young and tender plant. There are cases, however, when a frost is beneficial.

Then again, while rain is needed in fair quantity, too much of it is followed by rot and myriads of pests. If the planter desires anything at all when his crop is ripe, it is fine weather in which to gather his harvest.

Frequently large quantities of cotton are left on the plantations, because it is too wet to gather it. This happened a few years ago to an unusual extent, when a vast quantity of cotton had to be left upon the fields.

Of all the injurious agents most dreaded in the cotton-growing districts of the globe, none are so widely spread or so disastrous as "insect pests."

They attack different parts of the plant during its growth, and when the bolls are formed they commit great havoc among these by boring through and completely ruining the immature fibre. Then again, while the plant is young, they may attack the most tender portion of the plant, viz., the new and young leaves found at or near the top. This they soon clear and make their way as caterpillars down the plant, and they frequently clear it as though the leaves had been plucked off.

So completely do they do their work that it has been calculated in certain years the loss on this account alone cannot have been far short in America of 3? million pounds in one year.

Of the chief forms of insect pests, two specially stand out into prominence, both of which belong to the moth tribe of insects, viz., Alethia argillacea or Cotton Caterpillar, and the Heliothis armiger or Cotton Boll-Caterpillar.

The operations of the former are mostly confined to devastating the leaves and buds, while the latter confines its special attention to the bolls which, were they allowed to ripen, would burst with cotton.

The eggs of the former, too, are laid on the under side of the upper leaves and vast numbers are deposited. The moth flies by night, and the eggs laid are extremely difficult to discover-indeed it takes an expert to quickly find them.

Usually, about midsummer, the eggs are hatched in three or four days and then comes the period for spoliation.

All that is tender is assimilated, usually the under side of the young tender leaves found at the top of the plant.

During this stage of its existence the caterpillar moults five times and the larva period varies somewhat according to the weather from one to three weeks.

The chrysalis or pupa state covers from one week to four, and at last emerges as a beautiful olive gray moth with a purplish lustre.

In about four days the female commences to lay eggs very rapidly and will lay sometimes as many as six hundred during its life. No wonder, then, with several generations during a season and vast numbers of moths, that untold damages can be wrought by these particular insects in a single season.

A number of remedies has been successfully applied in the direction of spraying various chemical solutions, and in sowing plants which have had the direct effect of reducing the spread of this terrible pest. Its method of working can be seen on referring to Fig. 4.

Now the Boll-Caterpillar, though it lives much in the same way as the Alethia, has a very different method of procedure so far as its destructive habits are concerned.

And its fields and pastures, too, are by no means confined to one continent, or to one kind of plant, for it attacks both the tomato and corn plants. According to Dr. Howard, "It feeds upon peas, beans, tobacco, pumpkin, squash, okra, and a number of garden flowering plants, such as cultivated geranium, gladiolus, mignonette, as well as a number of wild plants." As the name indicates, the Boll-Caterpillar makes the boll its happy hunting-ground. The eggs are laid in the same way by the parent moth as the Cotton Caterpillar or Alethia, and when hatched the young powerfully jawed caterpillar makes its way to the newly-formed boll, and applying itself vigorously, very soon gains an entrance. Here it rests for a time, eating away at the best it can find. It ultimately emerges and is transformed into the pupa, taking up its quarters in the ground, until the next change takes place, when in a week or two's time it appears as a moth much the same in size as its cousin the Alethia, but coloured ochre yellow to dull olive-green and being more varied in its markings. It will lay during one season about 500 eggs.

Many remedies have been applied for the extirpation of this particular insect, but these only seem to have met with partial success. It will readily be seen how much more difficult this pest is to deal with than the preceding one. Living as it does in the boll and in the ground for a great part of its existence, it will be exceedingly difficult to get at.

In Mexico what is known as the Cotton-Boll Weevil (Anthonomus grundis) appears to do great mischief to the Cotton plant. It does most damage during the larv? stage, eating up the tender portions of the boll while in residence here. When matured it is only a little under half an inch in length.

Many other insects act injuriously upon the Cotton plant, but the following may be taken as the chief: Cotton Cutworm (Feltia malefida); Cotton lice (Aphis gossypii). Among the lepidoptera may be mentioned, Coc?cia rosaceana, or "Leaf-roller," so called from its habit of curiously rolling the leaves of the Cotton plant and then feeding inside the roll. Then grasshoppers and locusts occasionally do some damage, as well as a beetle named Ataxia crypta, which is noted for attacking the stalks of the Cotton plants, but it should be pointed out this beetle does not prey upon healthy and vigorous plants at all.

Scores of other insects could be mentioned as injurious, though some of them do but very slight damage indeed to the Cotton plant.

It does appear, however, from long years of experiment and observations, that little damage needs to be feared if the plants, while growing, and during the formation of the boll, can be carefully watched and guarded. The plants when matured are better able to withstand the onslaughts which these predaceous insects make upon them.

Then again, there are large numbers of physiological diseases of the cotton due to inherent weakness of the plant or failure of assimilative processes.

And lastly, vast numbers of fungi, too numerous to mention here, work serious injury to leaf, flower and boll in certain seasons of the year.

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