Effect of Foliar Fungicides On Hard Red Winter Wheat Grain Yield.

Foliar diseases can limit winter wheat grain yield in the southern Great Plains.  We evaluated the effectiveness of foliar fungicide in protecting winter wheat grain yield and quality of 23 wheat varieties commonly grown in Oklahoma. Quilt fungicide (1 L ha^-1) was applied to wheat at Feekes GS 9 using a split-plot arrangement of a randomized complete block design with four replications.   Wheat grain yield response to fungicide was greatest in the wheat varieties Jagger, Jagalene, and OK Bullet with foliar fungicide application resulting in grain yield increases of 1747, 1814, and 1411 kg ha^-1, respectively.  Additionally, these varieties showed the greatest test weight increases with 0.06, 0.05, and 0.06 kg L^-1.  Varieties such as Doans and Shocker were less susceptible to foliar disease and provided the least response to fungicide application with 269 and 202 kg ha^-1 increases in grain yield.  Fungicide application improved test weight and grain yield for all the winter wheat varieties in this study but the grain yield increases associated with foliar fungicide application were not always profitable.  Prices at the time of fungicide application and at harvest dictated that a yield increase of 157 kg ha^-1 would be required to offset the cost of the foliar fungicide, not including application cost.  Of the wheat varieties tested 22 out of the 23 met or exceeded this break-even yield requirement.  Overall, these data show that application of foliar fungicides to wheat might be warranted in the southern Great Plains when a susceptible variety is sown and yield potential is good.