The Effect of Chlormequat Chloride and Trinexpac-Ethyl Mixtures on Spring Wheat, Barley, and Oat Cultivar Lodging and Height in Alberta, Canada.

Crop lodging is a major production constraint that reduces spring cereal grain yield, harvestability, and grain quality in western Canada, especially when environmental conditions are favourable for high grain yields. Plant growth regulators (PGRs) that inhibit the production of gibberellic acid (GA), a plant hormone responsible for stem elongation, may prevent or reduce lodging in spring cereals. Chlormequat chloride (CCC) and trinexepac-ethyl (TXP) are PGRs new to western Canada, that inhibit the production of GA at different points in the same plant metabolic pathway, and they are applied at the beginning of stem elongation (BBCH 31) in spring cereals to reduce lodging. Preliminary fieldwork conducted in 2016 at 3 sites in central Alberta, Canada, demonstrated that a mixture of full-rate CCC and TXP was more effective in reducing height and lodging in spring wheat, oat, and barley than a full rate of each CCC or TXP alone. However, the optimal rate ratio of CCC and TXP mixtures for spring wheat, oats, and barley is unknown for western Canadian growing conditions and on localized cultivars. In 2017, fieldwork was initiated at 3 sites in central Alberta to investigate the efficacy of 25 rate combinations of CCC and TXP on the height and lodging of spring wheat, oat, and barley. In addition, the height and lodging effects of CCC alone, TXP alone, and a full-rate mixture of CCC and TXP was determined for 8 hard red spring wheat cultivars, 6 special purpose wheat cultivars, 6 oat cultivars, and 6 malt or feed barley cultivars to determine if response to CCC and TXP is cultivar-specific. Results from the 2017 growing season will be presented.