REDUCTION IN YIELD OF WINTER-WHEAT IN NORTH-CAROLINA DUE TO POWDERY MILDEW AND LEAF RUST

The relationships between yield reductions and severity of powdery mildew and leaf rust were examined on winter wheat cultivars Saluda and Coker 983. Plots were established in central and eastern North Carolina in the fall of 1987 and 1988. Triadimefon and/or benomyl were applied to wheat foliage for control of powdery mildew and leaf rust. Significant differences in disease development resulted from fungicide treatments, from differences in resistance of the cultivars, and from different environments. Differences in 500-kernel weight and grain yield were observed even when upper leaves had little disease in some environments. At one location in both years, tillers per meter row and kernels per head were reduced, apparently due to early-season powdery mildew epidemics. Both powdery mildew and leaf rust can reduce yield of winter wheat to a similar degree in the southeastern United States by occurring both before and after stem emergence.