Management of Volunteer Glyphosate-resistant Canola (Brassica napus L.) in Glyphosate-resistant Soybean (Glycine max L.) Crops
Mierau, Allyson N 1990-
In recent years, soybean acreage has increased significantly in western Canada. One of the challenges associated with growing soybean in western Canada is the control of volunteer glyphosate resistant (GR) canola, as the majority of soybean cultivars are also glyphosate resistant. The objectives of this thesis were (1) to determine the most effective combination of pre- and post-emergence herbicides to control volunteer GR canola in GR soybean; and (2) to determine the optimal soybean seeding rate and seeding date for soybean in western Canada to compete with volunteer canola, while still being economically feasible for producers. Experiments were conducted in 2014 and 2015 at three sites in Saskatchewan and one site in Manitoba. In the herbicide study, treatments consisted of combinations of one of three different pre-emergence herbicide treatments (2,4-D, tribenuron and saflufenacil) and five different post-emergence treatments (bentazon, imazamox+bentazon, cloransulam, thifensulfuron and fomesafen), as well as a glyphosate-only check. Treatments containing 2,4-D pre-emergence, thifensulfuron post-emergence or fomesafen post-emergence caused crop injury, while the remaining treatment combinations provided excellent volunteer canola control and low crop injury, with similar soybean yield results. The optimal combinations were tribenuron+imazamox+bentazon and saflufenacil+imazamox+ bentazon, as they contain the most herbicide groups, and therefore should be most effective at delaying herbicide resistance. In the cultural control study, soybean was seeded at five different seeding rates (targeted 10, 20, 40, 80 and 160 plants m-2) at three seeding dates (targeted mid-May, late May and early June). Soybean yield consistently increased with higher seeding rates, while volunteer canola biomass decreased, however seeding date results were inconsistent across site-years. An economic analysis determined that the optimal seeding rate was 40-60 plants m-2 depending on market price, while the optimal seeding date range was from May 22nd to June 1st.
DegreeMaster of Science (M.Sc.)
CommitteePozniak, Curtis; Shirtliffe, Steve; Warkentin, Tom; Eynck, Christina
Copyright DateMay 2017
integrated weed management