Abstract
In recent years, there has been a rapid increase in the number of herbicide-resistant weeds, including glyphosate-resistant (GR) biotypes in Ontario, Canada. A total of six field experiments were conducted over a two-year period (2018 and 2019) to determine the control of GR Canada fleabane (Conyza canadensis (L.) Cronq.) with currently available herbicides for winter wheat in Ontario. Winter wheat was not injured with any of the herbicides evaluated. Among herbicides evaluated, pyrasulfotole/bromoxynil (preformulated), 2,4-D ester, halauxifen, fluroxypyr/halauxifen (preformulated) + MCPA, pyrasulfotole/bromoxynil/fluroxypyr (preformulated), pyrasulfotole/bromoxynil/thiencarbazone (preformulated), pyrasulfotole/bromoxynil/thiencarbazone + MCPA, and fluroxypyr/halauxifen + pyroxsulam + MCPA controlled GR Canada fleabane 94–100% at 8 weeks after application (WAA) and reduced density 95–100% and biomass 97–100%. Reduced GR Canada fleabane interference with pyrasulfotole/bromoxynil/thiencarbazone + MCPA increased winter wheat yield 27% compared to the weedy control. GR Canada fleabane interference had no adverse effect on winter wheat yield with all other treatments. Based on these results, herbicide treatments that include 2,4-D, pyrasulfotole, or halauxifen can adequately control GR Canada fleabane in winter wheat.
Highlights
Winter wheat (Triticum aestivum L.) is a cereal crop in Ontario that growers often rotate with their soybean and corn crops
In a metaanalysis from trials conducted across North America, Flessner et al [6] reported an average of 22% winter wheat yield loss when Best Management Practices (BMP) were used and weeds were left uncontrolled
Reduced GR Canada fleabane interference with pyrasulfotole/bromoxynil/thiencarbazone + MCPA resulted in a winter yield increase of 27% relative to the weedy control
Summary
Winter wheat (Triticum aestivum L.) is a cereal crop in Ontario that growers often rotate with their soybean and corn crops. In a metaanalysis from trials conducted across North America, Flessner et al [6] reported an average of 22% winter wheat yield loss when Best Management Practices (BMP) were used and weeds were left uncontrolled. The herbicide that is used most frequently for GR Canada fleabane control in winter wheat is pyrasulfotole/bromoxynil (preformulated). + thiencarbazone-methyl, tribenuron-methyl + thiencarbazonemethyl + MCPA ester, fluroxypyr/bromoxynil/MCPA (preformulated), tolpyralate, and fluroxypyr/halauxifenmethyl + pyroxsulam + MCPA for the control GR Canada fleabane in winter wheat. No study has compared the efficacy of these herbicide options for the control of GR Canada fleabane in winter wheat in Ontario. Only effective herbicides will be applied which in turn will minimize the environmental loading of pesticides, improve weed control efficacy, and increase net returns to producers
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