Field Management of Late Blight of Tomatoes Caused by Phytophthora infestans Using Antibiotics from Streptomyces species

Abstract

Antibiotic culture filtrates from Streptomyces isolates coded 28P and CS35 were tested for efficacy in the control of late blight of tomatoes under field conditions. Crude culture filtrates, cell free culture filtrates, concentrated culture filtrates and a mixture of the two cell free culture filtrates were evaluated. Dithane M45 was used as a standard chemical check. The experiment was laid out in a Randomized Complete Block Design (RCBD) replicated four times with each treatment appearing once in each block. Concentrating culture filtrates by removing 30% of water enhanced their efficacy and the various culture filtrates had a significant (p<0.05) effect in controlling late blight disease. Mixing culture filtrates did not have significant (p<0.05) effect in improving efficacy in late blight management. Concentrating culture filtrates beyond 50% resulted in phytotoxic effects. The isolates had antifungal activity against Phytophthora infestans and with enhancement of this activity they can be used to manage the disease either alone or in IPM programmes.