CHAPTER 10 



Research on Insecticides 



Albert Hartzell 



The work on insecticides at Boyce Thompson Institute covering a period 

 of twenty years is briefly summarized in this chapter. This research has 

 centered mainly on contact poisons, such as pyrethrum, organic thiocya- 

 nates, and piperine, and also on greenhouse fumigants including naphtha- 

 lene and /3,i3'-dichloroethyl ether. The method of penetration of contact 

 sprays into insect integument and tracheae, and the mode of action and 

 neurotoxic effects on insects are described and illustrated. Such neurotoxic 

 action was found to be indicative of active compounds used in housefly 

 sprays. This led to a search for other neurotoxic compounds which has 

 followed two main lines: the preparation and testing of synthetic com- 

 pounds, and the extraction of plant products, which resulted in the dis- 

 covery that the alkaloid, piperine, a product of black pepper, is more 

 toxic to houseflies than pyrethrum. 



In addition to the main insecticide projects mentioned above, some local 

 insect control problems are briefly described. 



There is a great dearth of fundamental knowledge on the action of insecti- 

 cides. If the present account may be the means of inducing some young 

 scientists trained in the latest techniques in chemistry, physics, and biology 

 to become active in this field of research, it will have served its purpose; 

 for it is only by a fuller knowledge that the ever-present demand for insect 

 control will be alleviated. 



Efficiency and Mode of Action of Contact Insecticides 



A grant from the Herman Frasch Foundation for Research in Agricultural 

 Chemistry made it possible to direct attention to the factors affecting the 

 efficiency of contact insecticides ^^ and the mode of action of some of our 

 common insecticides on insects. Contact insecticides were selected for 

 this study because less was known of their action on insects. Contact 

 insecticides had been accepted and generally applied with httle or no 

 definite knowledge as to the basis of their efficiency. It was assumed by 

 many that contact sprays entered the spiracles and tracheae of insects, 

 thereby suffocating them. 



Microscopic examinations of dissected insects showed that spray solu- 

 tions fulfilling certain physical requirements entered the tracheae. The 



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