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Persistence of Glyphosate-Resistant Canola in Western Canadian Cropping Systems

^a Agric. and Agri-Food Canada (AAFC), Lacombe Res. Center, 6000 C&E Trail, Lacombe, AB, Canada T4L 1W1
^b AAFC, Lethbridge Res. Center, Box 3000, Lethbridge, AB, Canada T1J 4B1
^c AAFC, Beaverlodge Exp. Farm, Box 29, Beaverlodge, AB, Canada T0H 0C0
^d AAFC, Scott Res. Farm, Box 10, Scott, SK, Canada S0K 4A0
^e AAFC, Semiarid Prairie Agric. Res. Center, Box 1030, Swift Current, SK, Canada S9H 3X2
^f Dep. of Plant Sci., Univ. of Saskatchewan, Saskatoon, SK, Canada S7N 5A8
^g AAFC, Brandon Res. Center, Box 1000A, R.R. 3, Brandon, MB, Canada R7A 5Y3
^h Dep. of Plant Sci., Univ. of Manitoba, Winnipeg, MB, Canada R3T 2N2. Lacombe Res. Centre Paper no. 1080

View larger version (33K): [in a new window]   Fig. 1. Mean monthly precipitation data from April through October for the seven study sites. "Normal" is based on long-term precipitation data from each site.

View larger version (14K): [in a new window]   Fig. 2. Volunteer canola occurrence probabilities across all locations from 2001 to 2003. Rotation systems are wheat–pea–barley (WPB) or fallow–pea–fallow (FPF). Data are averaged across seeding systems to make ANOVA possible for all 2001 and 2002 intervals. Numbers above the data bars are the lower 95% confidence interval for the respective occurrence probability means. Occurrence probabilities are based on the proportion of quadrats in a particular treatment with at least one canola plant. P values show the statistical significance of the two rotation systems.

View larger version (34K): [in a new window]   Fig. 3. Volunteer glyphosate-resistant canola mean densities and standard errors at Beaverlodge, AB, from 2001 to 2003. Treatments include continuous cropping (wheat–pea–barley, WPB) or fallow (fallow–pea–fallow, FPF) rotations with five seeding system combinations: early, normal, and late seeding in low-disturbance, direct seeding (LDS), and high-disturbance direct seeding (HDS) and conventional tillage (CT) at normal seeding dates. Densities were determined at four intervals each year; preplanting (PREP), in-crop prespray (PRES), in-crop postspray (POST) (3–4 wk after herbicide application), and fall (FALL) (October). ANOVA results and contrast P values are given below the intervals with sufficient nonzero values to complete the ANOVA.

View larger version (31K): [in a new window]   Fig. 4. Volunteer glyphosate-resistant canola mean densities and standard errors at Lacombe, AB, from 2001 to 2003. See Fig. 3 for treatment labels and abbreviations.

View larger version (28K): [in a new window]   Fig. 5. Volunteer glyphosate-resistant canola mean densities and standard errors at Lethbridge, AB, from 2001 to 2003. See Fig. 3 for treatment labels and abbreviations.

View larger version (25K): [in a new window]   Fig. 6. Volunteer glyphosate-resistant canola mean densities and standard errors at Saskatoon, SK, from 2001 to 2003. See Fig. 3 for treatment labels and abbreviations.

View larger version (27K): [in a new window]   Fig. 7. Volunteer glyphosate-resistant canola mean densities and standard errors at Scott, SK, from 2001 to 2003. See Fig. 3 for treatment labels and abbreviations.

View larger version (27K): [in a new window]   Fig. 8. Volunteer glyphosate-resistant canola mean densities and standard errors at Swift Current, SK, from 2001 to 2003. See Fig. 3 for treatment labels and abbreviations.

View larger version (25K): [in a new window]   Fig. 9. Volunteer glyphosate-resistant canola mean densities and standard errors at Winnipeg, MB, from 2001 to 2002. No data were collected at Winnipeg in 2003. See Fig. 3 for treatment labels and abbreviations.

View larger version (33K): [in a new window]   Fig. 10. Volunteer glyphosate-resistant canola mean densities and standard errors across all seven locations from 2001 to 2003. See Fig. 3 for treatment labels and abbreviations. ANOVA and contrasts completed with locations treated as random effects.