Soft Winter Wheat Cultivar Response to Propiconazole and Ethephon

Components of intensive cereal management (ICM) systems such as high N fertility and close plant spacing can produce a dense plant canopy favorable to foliar diseases and lodging in soft winter wheat (Triticum aestlvum L.). Genetic disease resistance is often incomplete and a fungicide such as propiconazole (1‐{[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolan‐2‐yl] methyl {‐1H‐1,2,4‐triazole) can complement resistance for integrated disease control. The plant growth regulator (PGR) ethephon [(2‐chloro‐ethyl) phosphonic acid] can control lodging in soft winter wheat. The objective of this study was to evaluate the effects of propiconazole and ethephon on grain yield, test weight, plant height, lodging, and disease severity of 10 soft winter wheat cultivars in six Wisconsin environments. Although warm temperatures and dry conditions resulted in relatively low disease pressure, propiconazole increased grain yield 5.4 bu/acre and test weight 0.9 Ib/bu when averaged across environments and cultivars. Disease ratings of percent flag leaf covered by leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici) and Septoria leaf blotch [Macrosphaerella graminicola (Fuckel) Schroeter] were decreased 6.3 and 7.1, respectively. Reduction in leaf rust ratings for each cultivar correlated to yield and test weight increases from propiconazole application. Higher yielding cultivars responded more to propiconazole than low yielding cultivars and provided economic yield responses under most conditions of these experiments. The addition of ethephon to propiconazole decreased plant height by 2.4 in. and lodging by 38% over propiconazole alone. Ethephon produced its best economic response in one environment when lodging rating was reduced 60%. Environment × treatment and treatment × cultivar interactions were nonsignificant for all measures except disease ratings, where variability in disease development across environments and cultivars created different levels of response. Economic yield responses to propiconazole and ethephon under many of the conditions of these experiments show that fungicide and PGR inputs should be routinely considered for use in soft winter wheat production.