Other Promising Insecticides

After the potentialities of DDT as an insecticide were fully recognized, chemists began to make related materials in an effort to find more effective insecticides. Although DDT is still outstanding, certain close relatives show some promise. TDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane) was found to equal or perhaps slightly excel DDT against Anopheles larvae. It is less effective, however, against lice, flies, and mosquitoes.

Chemical 1068 is a recent material known only as 1068 (mixed isomers of C,,HCls), which was developed by the Velsicol Corporation and first reported upon by W. C. Kearns and associates of the University of Illinois. In preliminary tests it proved more toxic than DDT to the body louse, Anopheles larvae, houseflies, adult mosquitoes, and certain household pests. This chemical shows great promise, but further practical tests under a variety of conditions must first be made and information as to its toxicological effects on man and animals must be obtained before its value can be fully established.

A chlorinated camphene (3956), developed by the Hercules Powder Co., warrants further consideration, because preliminary tests show it to equal DDT in effectiveness against the body louse; it approaches DDT in its toxicity to mosquito larvae and adults and to the housefly. It also shows promise for use against ticks and mites.

Sabadilla is an old insecticide and a plant product that is said to be used by natives in South America to control lice on man. It has recently been investigated by T. C. Allen of the University of Wisconsin, and methods of handling the product have been developed that increase its effectiveness. It is a powerful toxicant for flies and mosquitoes, according to tests made by Allen and by E. R. McGovran at Beltsville. It is also one of the more effective materials that have been tested against the body louse.

Chloromethyl-p-chlorophenylsulfone, known as Lauseto Neu, was one of the most effective insecticides used by the Germans. It was tested against several pests after the war. It was found to be a good insecticide, but less effective against lice, flies, and mosquitoes than DDT. It is, however, one of the best chemicals tested against louse eggs.

Hydroxypentamethylflavan, developed by E. I. du Pont de Nemours & Co., Inc., was found by W. G. Bruce and C. N. Smith of the Savannah laboratory to be an excellent chemical for controlling chiggers in the ground. In comparative tests it proved more effective than benzene hexachloride. Since it does not possess the disagreeable odor of the latter compound, it will no doubt be the preferred treatment.

THEAUTHOR

E. F. Knipling is in charge of the Division of Insects Affecting Man and Animals in the Bureau of Entomology and Plant Quarantine. He has been with the Bureau since 1931, during which time his work has been almost entirely in the field of medical and veterinary entomology. During the war he was in charge of the Bureau's laboratory in Orlando, Fla., where he helped develop the methods used at home and abroad by the armed services for the control of disease-carrying insects. Mr. Knipling was awarded the United States of America Typhus Commission medal for his part in these developments.