Response on One Winter Wheat and Two Spring Oat Varieties to Foliar Applications of 2-Chloroethyl Phosphonic Acid (Ethrel)

Ethrel (2-chloroethyl phosphonic acid) has significant effects on growth and development of corn (Zea mays L.) and soybeans (Glycine max (L.) Merrill) and has been suggested as a potential male gametocide for the production of hybrid wheat. The purpose of this study was tofurther elucidate the response of winter wheat (Triticum aestivum L. em Thell.) and spring oats (Avena sativa L.) to foliar applications of Ethrel. Ethrel was foliarly sprayed on the winter wheat variety ‘Knox 62’ at 0.28, 0.56, 1.12, and 2.24 kg/ha when plants were in the late tillering, early boot, late boot, and heading stages. The magnitude of effects was closely related to rate and stage of application. Rates of 0.28 or 0.56 kg/ha applied at early and late boot stages of development effectively reduced height and lodging and in several cases accounted for significant increases in yield. Higher rates (1.12 or 2.24 kg/ha) reduced height and lodging but usually decreased yields when applied at the boot stages of growth. The 1.12 and 2.24 kg rates applied at heading stage did not decreas~ yield but were less effective in reducing height and lodging. Higher yields in the Ethrel-treated plots were generally associated with somewhat heavier seeds. Although we did not bag spikes or observe pollen from treated plants, the excellent seedset we obtained indicated that either the Ethrel treatments did not cause significant male sterility, or if they did, it was completely obscured by cross fertilization. Clearly female fertility was not impaired to any great extent by the Ethrel treatments. Our results with the same rates and stages of application for two oat varieties suggested that Ethrel has little potential for use on spring oats. Beneficial effects, such as reduced height and lodging, were accompanied by reduced yields. Even the lowest rate of application (0.28 kg/ha) applied at the late boot stage of growth caused a 40% reduction in grain yield. Reduced yields were accompanied by severe blasting of florets. Although the applications made at heading stage did not reduce yields, they were not very effective in reducing height or lodging.