The objective of this study was to survey pedigreed canola (Brassica napus L.) seedlots for contaminating herbicide resistance traits because of complaints from farmers regarding glyphosate [N‐(phosphonomethyl)glycine]‐resistant canola volunteers occurring unexpectedly in their fields at densities and in patterns that suggested that pollen‐mediated gene flow from neighboring fields in previous years was not the source of contamination. Twenty‐seven unique, commercial certified canola seedlot samples were collected. Glyphosate‐resistant seedlot samples were not collected. Canola samples were planted in the field, and when the canola had two to four true leaves, glyphosate, glufosinate [2‐amino‐4‐(hydroxymethylphosphinyl)butanoic acid], and thifensulfuron {methyl 3‐[[[[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)amino]carbonyl]amino]sulfonyl]‐2‐thiophenecarboxylate} herbicides were applied. Surviving canola plants were counted. Of the 27 seedlots, 14 had contamination levels above 0.25% and therefore failed the 99.75% cultivar purity guideline for certified canola seed. Three seedlots had glyphosate resistance contamination levels in excess of 2.0%. Unexpected contamination (even at 0.25%) can cause problems for producers that practice direct seeding and depend on glyphosate for nonselective, broad‐spectrum weed control. To avoid unexpected problems and costs, it is important that farmers are cognizant of the high probability that pedigreed canola seedlots are cross‐contaminated with the various herbicide resistance traits.

To investigate intercropping as a management strategy to increase crop productivity and weed suppression in organic systems, spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), canola (Brassica napus L.) and fi eld pea (Pisum sativum L.) monocultures were compared with two-, three-, and four-crop intercrops containing wheat at two organic and one conventional site in 2006 and 2007, central Alberta, Canada. We measured crop and weed biomass, grain yield, and crop competitiveness against weeds from a replacement design in a completely randomized block experiment. Pea and canola monocrops on organic sites yielded the least of all crop treatments. Conventional crop treatments generally yielded higher than organic treatments. Few land equivalent ratios (LERs) on organic sites were signifi cantly >1.0. Some wheat intercrops without barley showed overyielding (LER > 1.0) potential. Most of the signifi cant LERs were from three-and four-crop intercrops. More than 50% of the intercrops on organic sites signifi cantly suppressed weeds (based on relative weed biomass) and most of these intercrops had barley in the mixture. Barley as a sole crop and in intercrops suppressed weeds better than all other intercrops and sole crops. Th e wheatcanola intercrop exhibited the best weed suppression of the two-crop intercrops on organic and conventional sites. Th e crop densities used in this study may have contributed to the extremely low pea and canola monocrop yields as well as low LERs. Due to this, our fi ndings should be regarded as showing trends and potential from intercrops only. We therefore recommend further studies to establish ideal densities for the intercrops used.

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