Research on Aerial Spraying

Some day it may be said that the air age in insect control arrived with the discovery of the unusual values of DDT during the Second World War. In the two preceding decades, the application of insecticides by airplane had been tried against various pests, but the method was not used extensively except over cotton fields. Its advantages were recognized—large acreages could be covered quickly with no mechanical damage to the soil or to plants, and forest and swamps and other inaccessible places could be reached by air. There was one great limitation, though : The large quantity of insecticides that had to be applied for satisfactory control made the cost too high, even when the poisons were applied as undiluted dry powders. Liquid sprays, being less concentrated, required even greater quantities. DDT changed that situation. In their search for better insecticides for combatting malaria-carrying mosquitoes in the Pacific and other war theaters, entomologists found that DDT in an oil-solution spray gave good results when as little as one-fifth to one-fourth pound per acre was used. Engineers developed spraying apparatus for several types of military planes, and before long entire islands were being sprayed as a routine protective measure against mosquitoes and flies. The end of the war brought a great demand for adapting aerial spraying to a variety of civil needs. Stimulating influences were the publicity given wartime developments, the availability of war-surplus airplanes at low prices and former military pilots who wanted peacetime occupation in aviation, the discovery of other insecticides, and in-