Seed treatment with pyroquilon for the control of leaf blast in Brazilian upland rice

Abstract

Abstract The effect of seed treatment with pyroquilon fungicide on rice leaf blast caused by Pyricularia oryzae Cav. was studied in field and blast nursery experiments. In the field, pyroquilon (4.0 g/kg seed) treatment kept leaf blast severities below 5% at 38 days after sowing (d.a.s.) in susceptible cultivars (cvs) IAC 47, IAC 25, IAC 164, and L‐50. In the blast nursery experiment, seed treatment with carbofuran insecticide did not affect the efficiency of pyroquilon. Seed treatment with pyroquilon (4.0 g/ kg seed) or pyroquilon (4.0 g/kg seed) + carbofuran (4.8 g/kg seed) significantly reduced leaf blast at 38 d.a.s. in cvs IAC 25, IRAT 112 and IAC 47. Leaf blast and biomass production at 58 d.a.s. were negatively correlated (r = ‐0.91, ? = 0.01). Under low disease pressure, pyroquilon seed treatment reduced leaf blast severity at rates of application ≥ 2.0 g/kg seed. At high disease pressure, higher rates of application (4.0 g/kg seed) were found necessary for maximum disease control in a susceptible cultivar. Seed treatment had little or no effect in more resistant cultivars. The results indicate that treating seed with pyroquilon provides adequate protection against rice leaf blast during the vegetative phase in susceptible cultivars.