Chemistry, Biological Activity, and Uses of Formamidine Pesticides

The formamidines, a relatively new group of acaricide-insecticides, are novel both in their range of biological activities and in their mode of action, which is presently unknown. This paper is a review of the historical development, properties, structures, uses, and chemistry of this group of pesticides, with particular emphasis on chlordimeform (Galecron or Fundal), N'-4-chloro-o-tolyl-N,N-dimethylformamidine, and amitraz, 1,3=di-(2,4-dimethylphenylimino)-2-methyl-2-azapropane. Their biological activity and uses are defined by their toxicity to spider mites, ticks, and certain insects, and they are particularly effective against juvenile and resistant forms of these organisms. A significant, but poorly understood feature of their field effectiveness is their breadth of toxic action which includes direct lethality, excitant-repellant behavioral effects, and chemosterilization. They are generally of low hazard for nontarget species with the significant exception of predaceous mites. Several aspects of the chemistry of these compounds are considered, including structure--activity relations, synthetic pathways, isomerism and configuration, and their chemical and environmental stability. A significant feature of the metabolism and toxicity of these agents is the possible activation of chlordimeform by N-demethylation in vivo. Strong evidence for this has been presented with the cattle tick, but recent results discussed here suggest that in other species, i.e., mice, German cockroaches or black cutworm eggs, N-demethylation is neither a strong activation nor a detoxication reaction.