Evaluation of Bacillus mycoides isolate BmJ and B. mojavensis isolate 203-7 for the control of anthracnose of cucurbits caused by Glomerella cingulata var. orbiculare

Bacillus mycoides isolate BmJ (BmJ) and Bacillus mojavensis isolate 203-7 (203-7) were tested in the greenhouse for their ability to control Glomerella cingulata var. orbiculare the causal agent of anthracnose of cucumber by induced systemic acquired resistance (SAR). BmJ and 203-7 delayed disease onset and reduced total (43% and 56%) and live spore production (38% and 49%) per mm2 of lesion area when used to induce SAR in cucumber. 203-7 also reduced lesion diameter. Induction by G. cingulata conidia resulted in delayed disease onset, reduction of number of lesions per leaf and lesion diameter. Assays of cucumber apoplastic proteins extracted 6 days after induction showed that BmJ increased β-glucanase activity by 135%, and 203-7 increased β-glucanase activity by 72% and peroxidase activity by 79% when compared to the water control. Acibenzolar-S-methyl induced the highest (P = 0.05) levels of chitinase (950%) and peroxidase (420%) activity compared to water controls. Field experiments (2004 and 2005) evaluated applications of BmJ and fungicides for the control of anthracnose in cucumber (var. ‘General Lee’) and cantaloupe (var. ‘Athena’). BmJ was compared to full and half labeled rate alternate applications of azoxystrobin and chlorothalonil, and BmJ with half rate of azoxystrobin and chlorothalonil. BmJ applied seven days before inoculation reduced disease severity by 41% in cucumber in 2004 and by 24–21% in cantaloupe for both years compared to water controls which was statistically equal to the fungicide treatments. The full and half rate fungicide program provided 97–37% disease reduction compared to water controls. BmJ applied one week before inoculation significantly reduced AUDPC (P = 0.05) in cucumber compared to the water control in 2004 on cantaloupe for both years while the full and half rate fungicide program were equivalent and provided the lowest AUDPC. No yield reduction was noted as a result of the disease or treatment for either cantaloupe or cucumber.