Improved chemical control of Conyza bonariensis in wheat limits problems in the following fallow |
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| Authors: | Steven Walker Michael Widderick Andrew McLean Tony Cook Bill Davidson |
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| Institution: | 1. Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, , Toowoomba, Queensland, Australia;2. Queensland Department of Agriculture, Fisheries and Forestry, , Toowoomba, Queensland, Australia;3. New South Wales Department of Primary Industries, , Calala, New South Wales, Australia |
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| Abstract: | Conyza bonariensis is a major weed infesting zero‐tilled cropping systems in subtropical Australia, particularly in wheat and winter fallows. Uncontrolled C. bonariensis survives to become a problem weed in the following crops or fallows. As no herbicide has been registered for C. bonariensis in wheat, the effectiveness of 11 herbicides, currently registered for other broad‐leaved weeds in wheat, was evaluated in two pot and two field experiments. As previous research showed that the age of C. bonariensis, and to a lesser extent, the soil moisture at spraying affected herbicide efficacy, these factors also were investigated. The efficacy of the majority of herbicide treatments was reduced when large rosettes (5–15 cm diameter) were treated, compared with small rosettes (<5 cm diameter). However, for the majority of herbicide treatments, the soil moisture did not affect the herbicide efficacy in the pot experiments. In the field, a delay in herbicide treatment of 2 weeks reduced the herbicide efficacy consistently across herbicide treatments, which was related to weed age but not to soil moisture differences. Across all the experiments, four herbicides controlled C. bonariensis in wheat consistently (83–100%): 2,4‐D; aminopyralid + fluroxypyr; picloram + MCPA + metsulfuron; and picloram + high rates of 2,4‐D. Thus, this problem weed can be effectively and consistently controlled in wheat, particularly when small rosettes are treated, and therefore C. bonariensis will have a less adverse impact on the following fallow or crop. |
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| Keywords: | 2 4‐D aminopyralid fluroxypyr MCPA metsulfuron picloram |
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