Browsing by Author "Ghani Zadeh H"

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    Is glyphosate-resistant ryegrass resistant to paraquat?
    (Caxton Press, 2017) Ghani Zadeh H; Harrington KC
    Sequestration of herbicide into vacuoles is considered to be the main mechanism of resistance to both glyphosate and paraquat worldwide. In New Zealand, the first case of glyphosate resistance was found in ryegrass (Lolium) species, and the restricted herbicide translocation was found to be the main mechanism of resistance in the studied populations, presumably through sequestration. Overseas researchers hypothesised that the mechanism responsible for glyphosate resistance could also cause resistance to paraquat. We examined this hypothesis by comparing a known glyphosate-resistant population of perennial ryegrass with a known susceptible population after spraying with different rates (25–800 g ai/ha) of paraquat. The glyphosate-resistant population responded similarly to the susceptible population at the different rates of paraquat application. This result suggests that the restricted glyphosate translocation mechanism does not necessarily lead to paraquat resistance. These results also suggest that paraquat could be useful for controlling ryegrass when glyphosate resistance has evolved and the application of paraquat is permitted.
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    Pasture damage from spot-sprayed herbicides
    (Caxton Press, 2017) Harrington KC; Ghani Zadeh H; Moyo C; Kemp PD; Eerens JPJ
    Spot-spraying weeds in pastures enables the use of herbicide that would be too harmful to pasture if boom-sprayed. However, some herbicides are more damaging than others. To quantify this damage, a range of spot-spraying treatments was applied to ryegrass/white clover pastures. Four herbicide treatments were compared, each at two application rates and two sizes of sprayed patch. Applications of either clopyralid or a triclopyr/picloram mix resulted in total removal of white clover from the sprayed patches but these patches remained covered in perennial ryegrass. Metsulfuron also removed all white clover but also severely damaged the perennial ryegrass, although some grass cover remained due to survival of browntop. Residues of these treatments suppressed seedlings of white clover and weeds for many weeks after application. Glyphosate treatments resulted in the most bare soil. White clover recovered most rapidly in glyphosate-treated areas, mainly by lateral spread of stolons, but weed species also established rapidly.