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Is barnyard grass the next threat to cotton?

In a recent northern region WeedSmart trial, more than twenty per cent of barnyard grass samples tested were found to be resistant to glyphosate, with another twenty per cent identified as developing resistance.

Dr Chris Preston, University of Adelaide will be speaking about residual herbicides and how to correctly use them to minimise resistance in problem weeds such as barnyard grass.

Dr Chris Preston, University of Adelaide will be speaking about residual herbicides and how to correctly use them to minimise resistance in problem weeds such as barnyard grass.

Conducted last summer, the trial tested 30 samples of suspected glyphosate resistant barnyard grass submitted by agronomists from northern NSW and southern Queensland. The results provide a snapshot of the growing problem of resistance in these areas.

Most growers and agronomists in the northern cropping areas are aware of the rising risks associated with glyphosate resistance and are keen to know what their options are for regaining the advantage. A robust residual herbicide package, combined with a knockdown or double knock, is essential to drive down weed numbers early in the crop. Growers and agronomists should work together to develop a plan to rotate and mix pre-emergent herbicides and take advantage of the new herbicides that have been registered for weed control in recent years. Plan to use them carefully to get best results and make them last.

Planning for weed control across the whole rotation is a complex business that requires growers and their advisors to be well-informed and up-to-date with the latest advances in crop and weed science.

To assist, University of Adelaide’s Dr Chris Preston delivered the latest information on best use of residual technology to combat weeds and minimise herbicide resistance when he spoke at the WeedSmart-Monsanto event ‘More cotton, fewer weeds’ on Thursday 3 December, 2015.

“Some of the earlier practices regarding residual herbicides need to be reconsidered in light of greater experience under different field conditions and changes in sowing technology,” Chris says.

“Residual herbicides on the market vary in their water solubility, ability to bind to soil components, behaviour under different soil moisture conditions and rate of degradation over time,” he says. “Unfortunately, the seasonal conditions that unfold can have a significant effect on the efficacy of any product applied.”



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