Early fruit setting of tomatoes in experimental plots at Riverside, California, has been light in recent years. Unfavorable temperatures in late spring are a probable cause, but increasing atmospheric pollutants may also be involved since phytotoxic levels of total oxidants occur frequently in this area.

Suspensions of Fusarium lycopersici and Verticillium alboatrum for this study were provided by Professor Stephen Wilhelm, Department of Plant Pathology, University of California, Berkeley.