Survey of herbicide-resistant wild oat (Avena fatua L.) in two townships in Saskatchewan
The objective of this study was to determine the nature and occurrence of herbicide resistance in wild oat in the Grassland and Parkland regions of Saskatchewan in 1997, based on a systematic survey of fields in two randomly selected townships. The survey found that: 1) over one-half of fields in both townships had populations resistant to Group 1, 2, and/or 8 herbicides; 2) fields in the Parkland township had higher mean levels of Group 1 resistance (% resistant seeds) than fields in the Grassland township, suggesting they were subjected to more Group-1 herbicide applications; and 3) single- (Groups 1, 2, or 8) and multiple-group resistance (1,2; 1,8; 2,8; 1,2,8) were exhibited in populations in fields in both townships. The proportion of fields with populations exhibiting Group 1 (single) resistance was higher, and Group 2 and Groups 1,2 resistance were lower in the Parkland compared to that in the Grassland township. In both townships, farmers with more land (within the township or total farmed) tended to have a greater proportion of that land infested with Group 1- or 2-resistant wild oat compared to those with less land. The nature of resistance in wild oat populations in Saskatchewan is more diverse, differences in distribution and abundance of resistant biotypes between Grassland and Parkland regions are generally less apparent, and occurrence of resistance is more prevalent than previously documented.
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