The influence of simulated herbicide drift on canola (Brassica napus L.) and dry bean (Phaseolus vulgaris L.)
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Date
2003
Authors
Sawchuk, Jaret William
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Abstract
A field experiment was conducted over two years at two sites to determine yield and quality loss in canola and field beans in Manitoba, as a result of simulated herbicide drift of MCPA, glyphosate and thifensulfuron:tribenuron (2:1). Experimental design was a randomized complete block with four replicates. Five dosages of each herbicide, along with an untreated control, were applied in each crop to simulate herbicide drift. In canola, dosages of MCPA ester were 0, 25, 50, 100, 150, and 280 g ai/ha dosages of glyphosate were 0, 13, 25, 50, 100, and 200 g ai/ha while dosages of thifensulfuron:tribenuron were 0, 0.01, 0.05, 0.15, 0.5, and 2 g ai/ha. In field beans, dosages of MCPA ester were 0, 50, 100, 280, 560, and 1120 g ai/ha, dosages of glyphosate were 0, 30, 60, 125, 250, and 500 g ai/ha; while dosages of thifensulfuron:tribenuron were 0, 0.3, 1, 3, 6, and 12 g ai/ha. Dosages varied slightly in 2002. A nonionic surfactant (Agral 90) was added at a rate of 1% v/v to the glyphosate and thifensulfuron:tribenuron treatments. Assessments of herbicide effect included visual injury, stand density, shoot biomass, pods per plant, seeds per pod, 1000 seed weight, and grain yield. In general for both crops and all three herbicides, increasing herbicide dosage resulted in decreased final yield, with field beans being surprisingly tolerant to MCPA ester and thifensulfuron:tribenuron. For canola, the most damaging herbicide in terms of effect on yield vs. percent of field rate was thifensulfuron:tribenuron (2:1). The simulated herbicide drift of thifensulfuron:tribenuron (2:1) at a rate of 13 percent of the field rate (15 g ai/ha) caused a 46 percent decrease in yield. A 50 percent yield loss in the canola plots treated with glyphosate occurred at 23 percent of the field rate (440 g ae/ha). A 50 percent yield loss in the canola plots treated with simulated herbicide drift of MCPA occured at 18 percent of the field rate (280 g ae/ha). For field beans, the most damaging herbicide in terms of effect on yield vs. percent of field rate was glyphosate. A 48 percent yield loss in the bean plots treated with glyphosate occurred at 28 percent of the field rate (440 g ae/ha). The simulated herbicide drift of thifensulfuron:tribenuron (2:1) at a rate of 80 percent of the field rate (15 g ai/ha) caused only a 25 percent decrease in field bean yield. A 25 percent yield loss in the bean plots treated with simulated herbicide drift of MCPA occurred at 400 percent of the field rate (280 g ae/ha).