1999 Volume 65 Issue 5 Pages 543-548
Pre-inoculation with a suspension of 106conidia/ml of Exserohilum monoceras, a pathogen of Echinochloa species, within the 7 days prior to challenge inoculation with Pyricularia oryzae, reduced the number of rice blast lesions in the greenhouse, regardless of rice variety. In the field, a single foliar application of a conidial suspension of E. monoceras reduced lesions on leaves by more than 85% in the 2 to 6 weeks after application. Blast on non-inoculated leaves in these plots was also suppressed. The result suggests that inhibition of primary blast development by the application will reduce the chance of new infections to upper leaves, although E. monoceras did not induce systemic host resistance in the greenhouse test. Double, triple and quadruple applications with a week between applications, produced the same results. Transplanting E. oryzicola plants with disease caused by E. monoceras between rice hill rows in paddy fields, also suppressed blast, suggesting that conidia from lesions on diseased E. oryzicola plants may be dispersed to rice plants and suppress blast. Moreover, the effect of the application of E. monoceras on rice growth and yield was examined in a paddy field and compared with that of commonly used chemical fungicides. Single and double applications did not affect plant culm length, panicle length, panicle number, plant dry weight or grain yield, whereas triple applications reduced culm length, and the quadruple application reduced culm length, plant dry weight and grain yield. Provided that it is not applied more twice, E. monoceras is a promising biological agent for the control of rice blast with no adverse effects on rice growth and grain yield.
