McNaughton, K. E., Blackshaw, R. E., Waddell, K. A., Gulden, R. H., Sikkema, P. H. and Gillard, C. L. 2015. Effect of application timing of glyphosate and saflufenacil as desiccants in dry edible bean (Phaseolus vulgaris L.). Can. J. Plant Sci. 95: 369–375. Early application of desiccants in dry edible bean may cause yield reductions and unacceptable herbicide residue levels, resulting in rejection of exported shipments. The effect of application timing of two registered desiccants, glyphosate and saflufenacil, was examined in 12 field trials conducted over a 4-yr period (2009–2012) at Exeter, Ontario, Carman, Manitoba, and Lethbridge, Alberta. Desiccants were applied alone and in combination at five crop maturation stages. When glyphosate or saflufenacil alone, or in combination, was applied at 100% crop maturity, herbicide residue levels were acceptable (less than 2.0 and 0.01 ppm for glyphosate and saflufenacil, respectively) and there was no reduction in yield or hundred seed weight. Glyphosate residues remained below 2.0 ppm when the desiccant was applied alone or with saflufenacil at 75% crop maturity, but crop yield decreased by 16% compared with the untreated control when glyphosate and saflufenacil were combined. Residue levels were unacceptable when glyphosate was applied at 0, 25, and 50% maturity; generally the earlier glyphosate was applied, the greater the residue concentration in the seeds at harvest. Although no application timing resulted in saflufenacil residues above 0.01 ppm, crop yield was reduced when the desiccant was applied at 0, 25, 50, and 75% crop maturity. This information will provide dry bean processors with the necessary information to design guidelines concerning the application timing of glyphosate and saflufenacil so that bean yield and quality remain unaffected and seed residues remain below accepted levels.
Yield, germination and herbicide residue in seeds of preharvest desiccated wheat
