Rust (Puccinia emaculata) Management and Impact on Biomass Yield in Switchgrass

Area of Science:

• Plant Pathology
• Agronomy
• Agricultural Science

Background:

• Switchgrass (Panicum virgatum) rust, caused by Puccinia emaculata, is a significant disease impacting biomass yield for bioenergy and livestock.
• Effective disease management strategies are crucial for optimizing switchgrass production.

Purpose of the Study:

• To evaluate the efficacy of different fungicides (azoxystrobin, chlorothalonil, myclobutanil) and application intervals for controlling switchgrass rust.
• To assess the impact of rust disease and fungicide treatments on switchgrass dry biomass yield.

Main Methods:

• Fungicides were applied at 1-, 2-, 3-, or 4-week intervals over 12–14 weeks to switchgrass cultivar 'Cloud Nine'.
• Rust severity was monitored, and dry biomass yield was measured annually.
• Statistical analyses, including linear regression, were used to determine relationships between disease, treatments, and yield.

Main Results:

• Azoxystrobin and myclobutanil demonstrated superior rust control compared to chlorothalonil, especially at shorter application intervals.
• Fungicide treatment and application frequency significantly influenced dry biomass yield, with azoxystrobin and myclobutanil providing better yield protection.
• Rust severity was correlated with biomass yield loss, with an estimated 3–5% yield decline per 10% increase in leaf necrosis.

Conclusions:

• Frequent application of azoxystrobin or myclobutanil is recommended for effective switchgrass rust management.
• Failure to manage rust can lead to substantial reductions in switchgrass biomass yield, potentially 24–40% under severe conditions.