Optimum Spray Timing for Rice Panicle Blast Observed from Dosage-Effect Relationship and the Effect of 1980 Cold Summer on its Efficiency and Spray Timing

Abstract

Optimum spray timing and the dosage needed for protective values of 0.9-0.6 of panicle blast control in 1980 cold summer condition were estimated from the relationship between protective value (H) and dosage (G); H=Gⁿ/(φⁿ.+Gⁿ).
Optimum spray timing were 5 days (early heading stage) and next 12 days (late booting stage) before heading stage. Comparing 1979 test result the 1980 cold summer affect its efficiency and the optimum spray timing. Optimum spray timing under the delaying condition of panicle heading by cold summer were proposed.