Agronomic and Economic Response of Hard Red Winter Wheat to Foliar Fungicide in the Southern Plains

Hard red winter wheat yield losses from foliar disease in the southern Plains are estimated at 3 to 10% annually. We evaluated the agronomic and economic response of 20 to 22 hard winter wheat cultivars at two sites in Oklahoma from 2005 to 2010 (harvest years). Mean grain yield of susceptible cultivars treated with a foliar fungicide was 10% greater than the same cultivars nontreated at the Apache, OK, site, but foliar fungicide application had no effect on mean grain yield of intermediate or resistant cultivars. Mean grain yield of resistant, intermediate, and susceptible cultivars treated with a foliar fungicide were 10, 11, and 24% greater, respectively, than the same cultivars nontreated at Lahoma, OK. Foliar fungicides had greater than 80% likelihood of producing grain yield advantages necessary to offset foliar fungicide cost in nine out of 36 wheat and fungicide price scenarios at Apache and 35 out of 45 scenarios at Lahoma. Differing results at the Apache and Lahoma sites, which are approximately 105 miles apart, indicate that wheat response to foliar fungicide application can vary greatly even within a relatively small geographic area. Our results indicate that application of foliar fungicides to wheat have a high likelihood of generating positive returns in environments with high incidence and severity of foliar disease, but wheat grain yield response to foliar fungicides is not restricted solely to susceptible cultivars.