MOSQUITO CONTROL TESTS — STAGE 359 



parison with their great abundance in nearby villages and rice fields 

 where the sprays had not been applied. 



The reduction of malaria during the first season was diflB.cult to 

 estimate because of the manner in which notifiable diseases were re- 

 corded. Now, however, after 3 years of treatments, we are justified 

 in claiming a great reduction in numbers of anopheline adults and 

 larvae and a significant reduction in incidence of malaria. Also, the 

 families whose dwellings were treated have been blessed with reduc- 

 tions in numbers of flies, fleas, bedbugs, cockroaches, and other un- 

 welcome insects. 



THE USE OF A WETTABLE DDT POWDER IN THE TROPICS 



The early formulations of DDT included solutions, dusts, and oil 

 concentrates, the last-named intended for dilution with water to make 

 an emulsion. Each had its advantages and disadvantages. There 

 remained a need for a spray that could be used without creating a fire 

 hazard and one that could be used safely on animals. 



In 1945 there appeared new products in powder form containing 

 various amounts of DDT. These powders contained a wetting agent, 

 which made them compatible with water and permitted them to go 

 into suspension. Sprays made of wettable DDT powder might be 

 used on foliage, on the surface of buildings, and on animals without 

 absorption. They certainly would offer no fire hazard. But would 

 they kill insects ? Preliminary tests in the laboratory indicated effec- 

 tiveness equal to that of the emulsion and solutions, although the 

 action tended to be less rapid. 



In December 1945 a medical officer of the Aluminum Co. of America 

 called at our office to inquire whether there existed a DDT product 

 that could be used on dwellings of thatch and rough lumber without 

 creating a fire hazard. The company wanted to treat the dwellings 

 of its employees in two bauxite mining villages in Surinam (Dutch 

 Guiana), South America, as part of its progTam of sanitation and 

 malaria control. We told him that wettable DDT powders were avail- 

 able but that we had no precise information indicating whether they 

 would be effective; that the new formulations looked good but should 

 be tested on a practical scale by someone experienced in the use of 

 residual sprays and in control of mosquitoes and malaria. I could 

 see the possibility of an excellent research project through which the 

 company might obtain the information it sought and the Bureau of 

 Entomology and Plant Quarantine might obtain information that 

 would be useful to our military forces and also to our civilian popula- 

 tion across the United States. A cooperative agreement was signed 

 by officials of the Aluminum Co. of America and the United States 



