Abstract
Glyphosate resistant (GR) Canada fleabane has spread quickly across southwestern Ontario and new strategies for the control of this competitive weed must be developed especially in no-tillage crops. A premix of 2,4-D choline and glyphosate dimethylamine (DMA) has been developed for application on tolerant corn, soybean and cotton crops that provides an option for the control of this problematic GR weed. The objective of this research was to determine the required dose needed to effectively control GR Canada fleabane at different size categories in field and greenhouse experiments. In the field experiments, nine rates of 2,4-D choline/glyphosate DMA (53.8 to 13,760 g·ae·ha-1) were applied to GR Canada fleabane that were 10 cm in diameter/tall, 20 cm tall or 30 cm tall. Similarly, in the greenhouse, seven rates of 2,4-D choline/glyphosate DMA (0 to 3440 g·ae·ha-1) were applied to 10, 20 and 30 cm tall GR Canada fleabane plants. The three different size classes of GR Canada fleabane responded similarly to 2,4-D choline/glyphosate DMA in the field experiment. In the greenhouse there were some differences in control for the three size classes of GR Canada fleabane with 2,4-D choline/glyphosate DMA; the 20 and 30 cm tall plants required similar rates to provide equivalent control, but the 10 cm plants required a lower rate. In all situations, greater than 1720 g·ae·ha-1 of 2,4-D choline/glyphosate DMA was required to provide 95% control of 10, 20 and 30 cm tall Canada fleabane in greenhouse (35 DAA) and field experiments (8 WAA), respectively.
Highlights
Glyphosate resistant (GR) Canada fleabane [Conyza canadensis (L.) Cronq.] was first discovered in Ontario, Canada in 2010 at eight sites in Essex County [1]
Canada fleabane is well adapted to no-tillage crop production systems because its germination success is the greatest when the seed is on the soil surface [2]
There were no rates 1 days after the application (DAA) of 2,4-D choline/glyphosate DMA applied to 20 cm and 30 cm tall plants that provided 50%, 80% or 95% control of the Canada fleabane (Table 4, Table 5)
Summary
Glyphosate resistant (GR) Canada fleabane [Conyza canadensis (L.) Cronq.] was first discovered in Ontario, Canada in 2010 at eight sites in Essex County [1]. By 2012, 155 sites in eight Ontario counties had been confirmed with GR Canada fleabane [1]. Glyphosate resistant Canada fleabane has spread rapidly across southwestern Ontario because of its fecundity (up to 1 million seeds/plant) [2] and the long pappus attached to the small seed (1.3 mm long by 0.3 mm wide) which allows the seed to be wind dispersed up to 500 km from the parent population [3] [4]. Canada fleabane seeds can germinate year round, with the majority of seeds germinating in autumn and overwintering as a rosette and a smaller proportion of seeds germinating in the spring; this prolonged germination makes herbicide application timing very difficult [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
