Benzene Hexachloride

Benzene hexachloride, a synthetic compound that was discovered in England during the war, has also shown good possibilities for the control of some livestock parasites. It has not been available in the United States long enough or in sufficient quantity to permit more than preliminary tests. In the first tests it seemed superior to DDT for the control of cattle lice. It has also shown considerable promise for the control of cattle grubs, ticks, and mites. Tests in foreign countries, particularly in Australia, where more than 3,000,000 sheep have been treated with this material, have resulted in excellent control of the ked or sheep tick. This pest was eradicated with one treatment, and the residue remaining in the wool prevented reinfestation for a month or longer.

In contrast to DDT, which is ineffective for destroying insect eggs, benzene hexachloride appears to be a promising ovicide. Therefore, if further investigations confirm earlier results, it is possible that lice of cattle and other livestock can be eradicated with one treatment. This has not been possible with the older insecticides and only with higher concentrations of DDT, which are somewhat expensive. Where two or more treatments were necessary for eradicating an insect, as was the case with the older insecticides for cattle lice, the treatments had to be spaced at definite intervals based on the developmental period of the insect. That is often impossible because of unavoidable delays (in bad weather, for example) in applying the second treatment, and then eradication is not accomplished except by additional treatment.

Another promising insecticide developed during the war is benzyl benzoate. It was used effectively by the Army in the South Pacific for the protection of our troops against mites attacking man. It is likely, therefore, that benzyl benzoate may become an important insecticide for the control of mites attacking livestock.

Other new insecticides, especially some of the newest chlorinated compounds, have shown excellent results for controlling certain insects upon which they have been tested. Also new synergists, or activators, for some of our older insecticides have promise of being greatly superior to those formerly used.

THE AUTHORS

E. W. Laake, an entomologist in charge of the Kerrville, Tex., laboratory, has been with the Bureau of Entomology and Plant Quarantine since 1913. His work has concerned mainly insects affecting the health of man and domestic animals. Dr. Laake was president of the Texas Entomological Society from 1932 to 1934 and president of the Cotton States Branch of the American Association of Economic Entomologists in 1944.

W. G. Bruce is an entomologist in charge of the Savannah, Ga., Laboratory of the Division of Insects Affecting Man and Animals, Bureau of Entomology and Plant Quarantine. His first assignment with the Bureau was to study the ecology of the cattle grub in the Red River Valley. Since that time Mr. Bruce has conducted research on insects affecting animals in all sections of the United States. During the Second World War he was liaison officer between the Division of Insects Affecting Man and Animals and the various defense agencies in problems of insect control in military establishments.