Combined use of Streptomyces sp. A6 and chemical fungicides against fusarium wilt of Cajanus cajan may reduce the dosage of fungicides required in the field

Abstract Biological control agents offer one of the best alternatives to reduce the use of pesticides. This investigation studied the tolerance to fungicides and integrated use of the potential biocontrol agent Streptomyces sp. A6 for control of Fusarium wilt of pigeon pea, Cajanus cajan . Streptomyces sp. A6 exhibited strong tolerance towards most of the fungicides used in the study at concentrations higher than those recommended for field applications. The isolate showed enhanced growth and mycolytic enzyme production in the presence of sulphur, mancozeb, carbendazim, fosetyl aluminium and triadimefon. The fungicides mancozeb, sulphur and carbendazim were selected for further studies. Effective concentrations (EC 50 values) of the test fungicides that reduced Fusarium spore germination and fungal biomass by 50% were determined. Similarly, the EC 50 for inhibiting fungal spore germination and reducing fungal biomass to 50% by Streptomyces sp. A6 and culture filtrate (CF) were also determined. Combining the EC 50 dose of the culture and CF with test fungicides was found to be more effective for controlling Fusarium infection in C. cajan compared to the sum of the effects of the individual treatments. Such combined use of biocontrol agent with fungicides can reduce the dosage of toxic fungicides in agricultural fields, thereby reducing environmental risks. Tolerance and synergistic interaction of Streptomyces sp. A6 with frequently used fungicides suggested its potential in integrated pest management. To the best our knowledge, this is the first extensive study on integrated use of Streptomyces species with fungicides.