INERT COMPONENTS - ARE THEY REALLY SO

Zoosporic plant pathogens are associated with destructive root and fol iar diseases of numerous crops. This paper describes events which led to the discovery, specificity, and potential significance of surfactan ts (which are commonly considered the 'inert' components of many fungi cides) in the control of zoosporic pathogens. The latter include certa in downy mildews and numerous species in the genera Pythium and Phytop hthora. Zoospores are the weak link in the life cycle of these pathoge ns because they have no cell wall. The absence of a cell wall imparts a high degree of vulnerability to this spore stage and surfactants wer e demonstrated to rupture selectively the plasma membrane which encase s the zoospore, thereby resulting in the rapid death of the zoospore.