BACILLUS SUBTILIS FOR THE CONTROL OF POWDERY MILDEW ON CUCUMBER AND ZUCCHINI SQUASH

Abstract

Application of concentrated metabolites of Bacillus subtilis - CMBS - (5,000 µg/mL) one and 24 h before or after inoculation of Sphaerotheca fuliginea (3 x 104 conidia/mL) reduced the number of lesions on cucumber leaves by 90-99%. The average number of lesions on control plants was 16.7 per leaf. A wettable powder product formulated with cells (10%) and metabolites (10%) of B. subtilis (WPBS), and CMBS sprayed on cucumber plants (1,000 µg/mL and 10,000 µg/mL) twice a week totally controlled powdery mildew. In the control treatment, 18 days after the first spray, the percent leaf surface covered by lesions was 99.0 and 46.7%, on the cotyledonary and expanded leaves, respectively. In the control treatment, 30 days after the first spray, the percent leaf surface with lesions was 26.1%, while leaves sprayed with CMBS presented no lesions. The fresh weight per plant was 4.3 g in the control treatment; 12.2 g, and 10.2 g for plants sprayed with CMBS at the concentration of 1,000 and 10,000 µg/mL, respectively; and 9.7 g and 10.1 g for plants sprayed with WPBS 1,000 and 10,000 µg/mL, respectively. For zucchini squash, CMBS (5,000 µg/mL) sprayed every 2, 4, and 6 days showed reductions in lesioned leaf surface of 100.0, 98.3, and 94.7%, respectively.