Survey of herbicide-resistant wild oat (Avena fatua) in two townships in Saskatchewan

Abstract

The nature and occurrence of herbicide resistance in wild oat in annual crops grown in the Grassland and Parkland regions of Saskatchewan were determined in a systematic survey of fields in two townships in 1997. The survey found that over one-half of fields in both townships had populations resistant to Group 1 [acetyl-CoA carboxylase (ACCase) inhibitors], Group 2 [acetolactate synthase (ALS) inhibitors], and/or Group 8 (e.g., triallate, difenzoquat) herbicides. Forty-three percent of fields in the Grassland township and 48% of fields in the Parkland township had Group 1-resistant (HR) wild oat; 30 and 17% of fields in the Grassland and Parkland township, respectively, had populations exhibiting Group 2 resistance, whereas about 15% of fields in both townships had Group 8-HR wild oat. 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. Frequency of occurrence of resistance was not generally affected by farm size. The nature of resistance in wild oat populations is more diverse, differences in distribution and abundance of HR wild oat biotypes between Grassland and Parkland regions are generally less apparent, and occurrence of resistance is more prevalent than documented previously. Key words: Avena fatua, herbicide resistance, survey