Azoxystrobin Rate and Timing Effects on Rice Head Blast Incidence and Rice Grain and Milling Yields

Area of Science:

• Agricultural Science
• Plant Pathology
• Agronomy

Background:

• Rice blast (Pyricularia grisea) significantly reduces grain and milling yields in susceptible cultivars.
• Fungicide application is crucial for managing blast and ensuring crop productivity.

Purpose of the Study:

• To determine the optimal timing and rate of azoxystrobin application for effective rice blast control.
• To assess the impact of fungicide application timing on grain and milling yields under varying disease pressures.

Main Methods:

• Field studies conducted from 2001-2005 evaluated foliar azoxystrobin applications at different rates and growth stages (boot, heading, post-heading).
• Disease incidence was assessed before harvest, and grain/milling yields were compared between treated and untreated plots.

Main Results:

• Applications at heading (H), H+5 days, and boot+heading (B+H) significantly reduced blast incidence and increased yields, particularly under high disease pressure.
• Fungicide rates did not significantly affect blast control or yield when applied at H, B+H, or H+5.
• Late applications (B, H+10, H+15 days post-heading) were less effective, resulting in higher disease incidence and lower yields compared to heading applications.

Conclusions:

• Foliar azoxystrobin application at the heading stage or a combination of boot and heading stages is optimal for managing rice blast.
• Timely fungicide application is critical for maximizing grain and milling yields in susceptible rice cultivars.