Agronomic and Economic Response of Winter Wheat to Foliar Fungicides

Foliar diseases of winter wheat (Triticum aestivum L.) can reduce grain yield and kernel size. Foliar fungicides can reduce foliar disease losses, but effectiveness depends on rate and timing of application, environment, and cultivar response. These studies were conducted to determine the efficacy and economic feasibility of foliar applied fungicides for winter wheat. Field studies to determine effects of three to seven fungicide treatments on winter wheat grain yield, disease ratings, test weight, kernel weight, plant height, and lodging were conducted in six Wisconsin environments on two cultivars. Fungicides reduced disease ratings as much as 78%, increased kernel weight resulting in a decrease of 500 to 2400 kernels/lb, and increased grain yield from 9.5 to 36.3 bu/acre in environment 1 which had cool, moist weather that was conducive to disease development. Environments 2 to 6 had warmer, dryer conditions and, subsequently, less disease, but fungicides significantly reduced disease in these environments, increased kernel weight, in environments 2 and 5, and increased grain yield in environments 2 and 6. Propiconazole (1‐{[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3 dioxolan‐2‐yl]methyl}‐1H‐1,2,4‐triazole), trade name Tilt, applied at Zadoks growth stage (GS) 37 (flag leaf emergence) resulted in economic returns from grain yield in five and two of the environments for ‘Caldwell’ and ‘Argee’, respectively. Mancozeb (a coordination product of zinc ion and manganese ethylene bisdithiocarbamate), trade names Dithane M‐45, Manzate 200, Penncozeb, etc.) applied at GS 37 and 50 (head emergence) produced economic returns in four and two of the environments for Caldwell and Argee, respectively. Triadimefon, [1‐(4‐chlorophenoxy)‐3,3‐dimethyl‐1‐(1H‐1,2,4‐triazol‐1‐yl)‐2‐buanone], trade name Bayleton, applied at GS 37 gave economic returns in only three and one of the environments for Caldwell and Argee, respectively, because cost limited its economic benefits. Fungicides may give growers increased economic returns, however that probability is improved when differences in fungicide performance, cultivar disease reaction, and environmental conditions are considered.