From 1930 until 1945 the primary emphasis was on developing new methods or improving existing methods of control. The different methods were thoroughly tested under various climatic conditions. Plant bugs were causing serious losses in the irrigated localities of the Southwest. A mixture of 7.5 Percent Paris green and 92.5 percent sulfur was developed to fight them.

THUS THROUGH A HALF CENTURY control measures had been developed for all of the principal insect pests of cotton. The threat that the cotton industry in the United States might be doomed because of insects no longer existed. The insects had not been eradicated; in fact, they were far more numerous at the end of this period than they were at the beginning, but we had learned how to cope with them. Our success in controlling them only made conditions more favorable for their rapid increase when control was relaxed. It was inevitable that the fight against cotton insects would have to be continued. The cotton planter had become resigned to the fact that insect control was just as important a part of his normal farming operations as the selection of good seed, proper fertilization, or proper cultivation.

In 1945 a new era in the research began. The development of the new and more powerful organic insecticides opened up new avenues. But it likewise created new research problems.

The first experiments with the new organic insecticides proved that they were not cure-alls. DDT was the first to be tested extensively, followed by benzene hexachloride, toxaphene, and chlordane. These were found to be highly effective against certain insect pests of cotton and were adopted in the control recommendations of many States. But not one of these individually controlled all the major pests. Certain combinations were developed, such as 3 percent gamma isomer of benzene hexachloride-5 percent DDT-40 percent sulfur, 20 percent toxaphene-40 percent sulfur, and10 percent chlordane-5 percent DDT.

The synthesis of new organic compounds was greatly accelerated, and thousands were tested for insecticidal efficacy during the late 1940's and early 1950's. Aldrin, dieldrin, parathion, and tetraethyl pyrophosphate were included in the official recommendations of some States. Others, notably heptachlor, EPN (O-ethyl O-p-nitrophenyl benzenethiophosphonate), methyl ester parathion and a sterio isomer of dieldrin, showed considerable promise in later tests. Again, however, none satisfied the requirements for an all-purpose cotton insecticide. The most effective combinations have to be worked out for each State or area.

Certain organic insecticides can kill insects developing inside of plant tissue as well as those that feed on the exterior parts. Heptachlor, chlordane, aldrin, dieldrin, and (to a lesser extent) benzene hexachloride are known to kill boll weevils developing inside of punctured squares when applied to cotton under field conditions. This property may prove to be extremely important in fixing the ultimate value of the poisons used against cotton insects and may have far-reaching effects in developing better controls.

The organic insecticides in general lend themselves readily to incorporation into emulsifiable concentrates through the use of proper solvents and emulsifiers. Properly formulated, they can then be diluted with water and applied as low-gallonage, low-pressure sprays. The trend in the use of insecticides for cotton insect Control now is toward such sprays. In 1950 and 1951 millions of gallons of sprays were applied to cotton. Recent experiments have shown that as little as I gallon per acre of a concentrated spray containing the required amounts of the insecticide, or insecticides, may be enough. Since sprays can be applied under conditions that would render dusts ineffective, this research represents a distinct achievement. Many farmers apply concentrated sprays to cotton at the time they cultivate the crop, and thereby reduce the cost of application. Combination sprays have been developed for the simultaneous control of most cotton insects. They may be applied effectively by ground equipment and airplanes.

The development of proper schedules for applying insecticides to cotton has done much to lower the costs. Early season control programs that have been developed for many areas have been so successful as to make unnecessary additional applications later. Considerably smaller amounts of the insecticide per application are needed in the early applications. Killing off many insects of minor importance helps the plants to grow faster, so that the crop is usually matured earlier and the farmer has a better chance to get it properly harvested. Both dusts and sprays have been successfully used in early season control, but sprays appear to be preferable to dusts largely because they can be applied directly onto the small plants by the use of proper spray equipment, whereas with dusts there is some unavoidable wastage. Ground machines are also preferable to airplanes for applying sprays to cotton in the early season for the same reason.

The need for research stems from the fact that the value of the cotton destroyed by insects has averaged more than 100 million dollars annually since 1929, climaxed by an all-time-high loss of more than goo million dollars in 1950. The value of the research is shown by the thousands of farmers who have followed recommendations and have increased their yields three, four, and five times over comparable areas in which no control was used. Net profits due entirely to insect control of 150 to 175 dollars an acre and net returns of from 20 to 28 dollars for every dollar spent for insecticides have frequently been obtained by cotton farmers who followed research findings and recommendations. The difference between a profit and a loss on any given acre of cotton often depends entirely on whether the insects are controlled.

C. F. RAINWATER was reared on a cotton farm in southern Mississippi. Since graduating from Mississippi State College in 1931 he has been engaged in research on cotton insects in Louisiana, Florida, South Carolina, and Texas. Since 1948 he has been in charge of the basic cotton insect research laboratory at College Station, Tex.