Insects On Cotton

Progress in Research on Cotton Insects

C. F. Rainwater.

Cotton is a plant that nature seems to have designed specifically to attract insects. It has green, succulent leaves, many large, open flowers, nectaries on every leaf and flower, and a vast amount of fruit. All seem made to order for insects, some beneficial to man and some the boll weevil, bollworm, pink bollworm, cotton leaf-worm, cotton aphid, cotton fleahopper, tarnished plant bug, rapid plant bug, conchuela,. southern green stink bug, spider mites, grasshoppers, and thrips notoriously obnoxious.

The cotton leafworm was the first insect of major importance to deprive the early cotton grower of a substantial part of his crop. Records dating from the eighteenth century show that in some years it destroyed 25 to 90 percent of the cotton. Many early planters were keen observers of insects and accurately recorded descriptions of them, the type and amount of damage they caused, the time they appeared in various localities, data on life history, and the effect of predacious insects on them.

The bollworm became notorious early in the nineteenth century. It and the cotton leafworm often destroyed the crop completely in some localities. Many early writers and researchers could not differentiate between the bollworm and the cotton leafworm, and the estimates of damage by the two insects no doubt were often wrong.

Research by individual cotton planters was the chief source of information concerning cotton insects during the first half of the nineteenth century. The information was disseminated largely through individual correspondence and newspapers. The significance of some of the research and its accuracy is shown by the fact that it was a planter who first reported that the bollworm of cotton and the corn ear-worm are the same insect.

As the country grew and as cotton production increased, other insert pests appeared to plague growers. Stink bugs and aphids were known in 1855 to be serious pests of cotton. Planters often found it unprofitable to grow cotton because of insects. It became evident that the Government must take a hand in the study and control of the insects. Consequently the Congress ordered a special investigation of cotton insects in 1878.

The early studies were directed very largely at determining the life history and habits of the species that were then causing damage, the effects of their natural enemies, and cultural methods of control. The investigations provided much of the background for later control efforts.

The first successful control measures were cultural methods. Even today they are recognized as of fundamental importance. The early planting of early fruiting varieties of cotton, frequent cultivation, clean culture, cleaning up debris and fence rows around fields, and fall and winter plowing were early recognized as valuable aids in the control of the insects that attack cotton.

Artificial methods of control also received the attention of early research workers, both professional and laymen. They tried different kinds of attractants and repellents, poisoned baits, fires in the fields at night to attract insects, mechanical devices for dislodging and collecting the insects from the plants, and hand picking of the insects from the plants.

Plant breeders contributed a great deal to the research during the early 1900's. They undertook studies to develop varieties of cotton that could better withstand insect attack, varieties that were fast growing and early maturing so that the crop could be produced and matured before insects had time to build up to their maximum numbers, and more prolific varieties that could produce additional fruit after part of it had been destroyed. Indeed, plant breeding still has a vital part in research on the control of cotton insects.

Research on the chemical control of cotton insects really began in earnest in the early 1900's. Various chemicals were applied as sprays in the hope of finding effective controls. As early as 1905 Paris green was recommended as a spray to combat some of the insects. London purple and arsenate of lead also came into general use then. The methods of application were crude; that probably accounted largely for the failure to get effective control. One method, for example, was to stir the chemical in water and sprinkle it over the tops of the plants with a cedar bough. Another method was to drive small holes into wooden buckets or kegs and allow the solution to trickle through them on the plants. Nevertheless, sprays came into fairly general use during the period.

The part of the agricultural engineer was first realized fully during the early 1900's. The development of machines for applying sprays is one example of their early work. Various attachments were constructed and fastened onto the plow to knock the insects and the infested squares from the plant and collect them in some sort of container whereby they could be buried, burned, or otherwise destroyed. One widely recommended device was a chain drag, which pulled infested squares from under the plant and deposited them in the middle of the row so they would be exposed to the sun and the larvae in them would be killed.

The first arsenate of lead ever used in dust form for insect control was in 1908. From then until 1916, hundreds of experiments were conducted with dusts of lead arsenate, Paris green, and London purple. Against the cotton leaf-worm and certain other insects, the dusts were highly effective, but they never proved entirely satisfactory against the boll weevil or the bollworm. Emphasis continued to be placed on cultural methods of control for most cotton pests.

OF GREAT IMPORTANCE was the discovery in 1916 that calcium arsenate dust was highly effective against some cotton insects. For the next three decades, however, research on the control of cotton insects was largely devoted to developing dusts and dust mixtures and methods of applying them. It was demonstrated during this period that insect pests of cotton could be economically controlled and that cotton production could be made profitable even under conditions of heavy attack.

Meanwhile, another serious insect menace appeared. The pink bollworm, the most serious insect pest of cotton known in many parts of the world, was discovered in Texas in 1917. Many people realized that our cotton industry might be doomed if it were allowed to spread as the boll weevil had done. Research efforts were doubled therefore as to the biology, ecology, and control of the pink bollworm. The research provided the basis for the successful fight to prevent its spread to the principal cotton-producing areas through quarantine regulations and control efforts.