ANTIFUNGAL ACTION OF STREPTOMYCIN-COPPER CHELATE AGAINST PHYTOPHTHORA INFESTANS ON TOMATO (LYCOPERSICON ESCULENTUM)

The antifungal protection afforded by streptomycin-copper chelate in vivo in greenhouse tests against Phytophthora infestans on tomato was found to be of the order of six times greater than that of streptomycin sulphate. The copper chelate also showed much greater resistance to simulated rainfall. Similar tests showed that streptomycin- copper chelate (in terms of streptomycin content) was from 23 to 5 times more effective as an antifungal prophylactic spray than zinc ethylene-bis(dithio-carbamate) (zineb), and some fifty times more active than copper oxychloride formulated as a commercial 50 % wettable powder. These three materials showed roughly similar resistance to weathering by 'rainfall' and it was assumed therefore that 250 i.u./ml. streptomycin as streptomycin- copper chelate might be expected to give the same degree of protection against Phytophthora infestans in the field as would the usual field rates of usage of zineb and copper oxychloride.