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Spring Wheat and Barley Responses to Ethephon

Dep. of Agronomy and Plant Genetics, 411 Borlaug Hall, 1991 Upper Buford Cir., Univ. of Minnesota,, St. Paul, MN 55108

J. V. Wiersma, W. E. Lueschen and D. D. Warnes

Univ. of Minnesota Northwest Exp. Stn., Crookston, MN 56716
Univ. of Minnesota Southern Exp. Stn., Waseca, MN 56093
Univ. of Minnesota West Central Exp. Stn., Morris, MN 56267

^* Corresponding author

Ethephon [(2-chloroethyl) phosphonic acid] has recently been introduced in North America as a regulator to control lodging in cereals. A 3-yr study (1983-1985) was conducted to determine how widely grown spring wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.) cultivars in the North Central United States responded to ethephon. Nine randomized complete-block, split-plot experiments with wheat, and seven with barley, were conducted at the Crookston (soil classification, Aerie Calciaquoll), Morris (Aerie Calciaquoll), St. Paul (Typic Hapludoll), and Waseca (Aquic Hapludoll) Experiment Stations in Minnesota. Ethephon was applied at a rate of 0.42 kg a.i. ha^–1 in all years as well as 0.28 kg a.i. ha^–1 in 1985. When lodging occurred, ethephon treatment at either rate lessened its severity. Ethephon shortened crop height, more so when applied at the higher rate. Effects of ethephon on grain yields varied from significant reductions (average 13% for wheat, 9% for barley) to significant increases (average 12% for wheat, 13% for barley). Increases were most common when control plots lodged, although higher yields in response to reduced lodging were not obligatory. When lodging did not occur, ethephon treatment tended to result in reduced yields. Among barley cultivars, ‘Robust’ was most likely to exhibit reduced yields. Genotypic variability for ethephon sensitivity among wheat cultivars was less evident. In most experiments, ethephon treatment lowered kernel numbers per spike or mass per kernel. We conclude that ethephon use is most reasonable when the production practices followed, or environmental conditions, assure the likelihood of significant lodging. Further research investigating cereal responses to lower ethephon rates, as well as interactions between ethephon and plant stress, is needed.

Received for publication September 14, 1997.