Integrated biological and chemical control of rice sheath blight by Bacillus subtilis NJ-18 and jinggangmycin

BACKGROUNDSheath blight caused by Rhizoctonia solani Kuhn is a major disease of rice that greatly reduces yield and grain quality and jinggangmycin is the most widely used fungicide to control this disease in China. Bacillus subtilisNJ-18 has broad antimicrobial activity to many phytopathogenic bacteria and fungi; it is especially effective against Rhizoctonia solani. Laboratory, greenhouse and field tests were conducted to determine the effect of combining the biological control agent Bacillus subtilisNJ-18 with the fungicide jinggangmycin for control of rice sheath blight. RESULTSGrowth of NJ-18 in vitro was not affected by jinggangmycin. In a greenhouse experiment, disease control was greater with a mixture of NJ-18 and jinggangmycin than with either alone; a mixture of NJ-18 at 10(8)cfu mL(-1) and jinggangmycin at 50 or 100mgL(-1) reduced lesion length by 35% and 20%, respectively, and the combinations showed a synergistic action. In three field trials, disease control was significantly greater with a mixture of NJ-18 at 10(8)cfu mL(-1) and jinggangmycin at 75 or 150g a.i. ha(-1) than with either component alone. CONCLUSIONThe results of the study indicate that, when Bacillus subtilisNJ-18 strain was combined with jinggangmycin, there was an increased suppression of rice sheath blight, and thus could provide an alternative disease control option. (c) 2013 Society of Chemical Industry