Chemical control of upland rice blast: effects on fungi not targeted by phylloplane

Abstract

Upland rice blast significantly affects yield, requiring one or two fungicides applications to control it. However, the effect of fungicides on beneficial fungi and on fungi not targeted by rice phylloplane are unknown. This study aimed to evaluate the effect of fungicides on panicle blast control, on fungi not targeted by rice phylloplane, and to study the antibiosis of fungi not targeted by M. oryzae. A field experiment was conducted by using two cultivars (Primavera and Bonança), four fungicides (trifloxistrobina + propiconazol, azoxistrobina, tebuconazol, and triciclazol) and a control, with a randomized blocks design, in a split-plot scheme, and four replications. The panicle blast severity, leaf chlorophyll content, number of colony-forming units cm-² of leaf area, and antibiosis were assessed. The Primavera cultivar showed higher panicle blast severity than Bonança. The fungicides azoxistrobina and trifloxistrobina + propiconazol significantly differed from the control, showing the lowest panicle blast severities. The fungicides did not affect the chlorophyll content, but differences were noticed between the cultivars. The fungicides tebuconazol, trifloxistrobina + propiconazol, and azoxistrobina significantly reduced the phylloplane fungi, concerning the control. The triciclazol did not differ from the control, showing the highest number of colony-forming units cm-² of leaf area. Among the four fungi tested, only Epicoccum sp. showed antagonism to M. oryzae.

Keywords

• Oryza sativa L.
• Magnaporthe oryzae (Barr) Couch
• biocontrol
• antibiosis