Fungicide strategies and variety resistance for control of stripe rust in winter wheat

Benjamin Othniel Brimlow

Stripe rust of winter wheat (Triticum aestivum L.) can reduce grain yield, kernel size, and influence other agronomic and grain quality attributes. Foliar fungicides can protect against stripe rust losses, but effectiveness depends on fungicide mode of action, rate, timing, variety resistance, and environmental influence. These studies investigated stripe rust management strategies that can maximize profit for dryland wheat growers in eastern Washington. Stripe rust control and winter wheat plant responses were assessed for nine fungicide treatments on moderately susceptible, moderately resistant, and resistant winter wheat varieties. Fungicides differing in biochemical modes of action were applied at plant jointing, flag leaf, and anthesis stages. Field experiments were conducted in 10 environments, across three years that differed in stripe rust potential and wheat management. Fungicides effectively reduced stripe rust ratings at trials where disease was observed and moderately susceptible varieties responded greatest to treatments with little response differences between Tilt (propiconazol and Quilt (Propiconazol + Azoxystrobin).In 2012, plant height, test weight, disease rating, and protein responses to fungicide treatments were found in most trials, and some effects on plant height and percent protein were found without disease symptoms. Grain yield was 0.54 Mg ha-1 (p<0.001) higher due to Quilt Xcel treatments than Tilt treatments in the Dusty 2012 trial and similar responses were recorded at other trials with high stripe rust activity. In Pullman 2014, single fungicide applications produced 0.30 Mg ha-1 greater (p=0.003) grain yield than multiple sequential fungicide applications. Although grain yield was higher due to Quilt Xcel treatments compared to Tilt treatments in some environment and cultivar combinations, economic responses differed. Double sequential Tilt applications were the most economical treatment when averaged across varieties in high stripe rust environments, a $211 ha-1 increase over the non-treated on average. Single Tilt applications at Zadoks growth stage 37 increased economic returns by $93 ha-1 when averaged across varieties in low stripe rust environments, whereas double and triple sequential fungicide applications were generally not economical. Fungicides can provide protection against stripe rust injury and yield loss to winter wheat; however, consideration of fungicide material and timing, cultivar resistance, and environmental conditions are essential for optimizing economic control strategies of stripe rust.

Fungicide strategies and variety resistance for control of stripe rust in winter wheat

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