SECTION 3 



TOXICITY OF EXPERIMENTAL FOREST INSECTICIDES TO 

 FISH AND AQUATIC INVERTEBRATES 



Richard A. Schoettger and Wilbur L. Mauck 



INTRODUCTION 



In 1952, the U.S. Forest Service began aerial spraying of insecticides 

 to control outbreaks of the spruce budworm ( Cho>vu>tonewia 6wrru.6eAa.nd). 

 The first forest insecticide to be applied was the organochlorine com- 

 pound, DDT, which was commonly applied at a rate of 1.12 kg per 9.3 liters 

 per hectare (1 pound DDT per 1 U.S. gallon per acre). Applications of DDT 

 continued for nearly 20 years before its further use was prohibited in 

 1969 by the U.S. Environmental Protection Agency. However, this com- 

 pound was banned in the State of Maine for use as a forest insecticide as 

 early as 1967. 



DDT was of particular concern to environmental scientists because of 

 its persistence, toxicity and bioaccumulation in non-target organisms. As 

 early as 1963, DDT was recognized as an imminent hazard to terrestrial, 

 avian, and aquatic fauna by the President's Science Advisory Committee. 

 This committee recommended a reduction in the use of persistent pesti- 

 cides. Certain uses of DDT were prohibited by the U.S. Department of Agri- 

 culture (USDA) in 1969 and an informal review of the remaining uses con- 

 tinued through 1970. On the basis of some 10,000 pages of testimony by 

 more than 50 scientific experts, the Administrator of the Environmental 

 Protection Agency issued an opinion and order, published July 7, 1972 in 

 the Federal Register, cancelling or suspending all uses of DDT, except 

 those related to human health (USDA, 1973). 



After the banning of DDT, government officials and environmentalists 

 urged the development and use of insecticides that were highly specific in 

 their action, were more readily biodegradable, and did not bioaccumu- 

 late. Because research on radically new methods of control might consume 

 excessive time or be unproductive, the U.S. Forest Service decided that 

 investigations of DDT replacements should be directed only to chemicals 

 already in production, or experimental compounds near the production stage 

 (Schmiege et at, 1970). Also, the compounds selected should be applied 

 from the air, by spraying procedures that had been developed for DDT. 

 Three conditions were to be met: (1) the insecticide should be more toxic 

 to the western spruce budworm than to other organisms; (2) the insecticide 

 and its degradation productions must not accumulate in plants or animals 



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