Toxicity and Acceptance of Some Pesticides Fed to Parasitic Hymenoptera and Predatory Coccinellids1

Abstract

A survey of our present knowledge of the most suitable pesticides and their most effective use in integrated chemical and biological control has indicated that stomach poisons have several advantages. A review of the processes through which the favorable selectivity of stomach poisons on pests and natural enemies may arise suggested the possibility of transforming contact pesticides into stomach poisons to increase their specificity and advantageous selectivity to natural enemies. A method of measuring stomach-poison activity exclusive of contact effect was developed and used to assess the effects of commercial formulations of 61 common pesticides as food contaminants to 2 representative species of parasitic Hymenoptera and 2 coccinellids. Data on the acceptance and toxicity of 2 concentrations of each pesticide are presented, most materials were at least in part gustatory repellents. Mortality was often unexpectedly rapid, sometimes occurring following tasting and immediate rejection. Many chlorinated hydrocarbons were innocuous as stomach poisons to the natural enemies tested. The most toxic materials were usually among those most poorly accepted. Since a taste of a violent poison was fatal, distastefulness of a very toxic material afforded no protection. Specificity recognizable among contact poisons was exaggerated with ingestion. A probable source of favorable natural-enemy selectivity seemed to lie in the high degree of inactivation of some pesticides in the digestive tracts of the natural enemies tested.