Herbicide tolerant crops and weed population dynamics in western Canada

摘要

Both genetically modified and conventionally derived herbicide-tolerant canola varieties have been available on a commercial basis in western Canada for five years. Approximately 80% of the 5.6 million ha of canola grown in 1999 were herbicide tolerant. These new technologies have offered producers a means of controlling previously manageable weeds, controlling herbicide resistant weeds and diversifying cropping systems. Weed populations have been changed by these new modes of action within canola crops, but long-term changes in weed dynamics have not occurred. Controlling volunteer canola has become more complex. The potential for adverse changes in weed community composition exists if this technology becomes the dominant selection pressure acting on weeds due to the increased frequency of canola within rotations or the introduction of herbicide tolerant cereal crops. Changes are more likely to occur in reducedtillage systems where there is a greater reliance on glyphosate and could compromise the sustainability of conservation tillage in the semi-arid regions.