Volunteer barley is making its presence felt in a major way in wheat crops across the country this spring, according to the latest technical helpline reports from Monsanto Crop Protection.

Monitor (sulfosulfuron) was found to have the best activity against barley volunteers.

And with no products having specific approval for the problem, maximum advantage will have to be taken of incidental control from spring grass weed herbicides.

“With over 750,000 ha of spring barley grown last season in the wake of 2008’s especially challenging autumn crop establishment conditions and much of this land going back into wheat last autumn, it’s hardly surprising there are so many volunteers about,” observes Monsanto technical agronomist, Rob Plaice. “Especially so given the extent to which the dry September got in the way of effective Roundup stubble control.

“This problem really needs to be addressed to minimise the substantial competitive effect it can have on wheat yields, serious seed and milling crop contamination issues and massive seed return into following crops. But this is easier said than done as no wheat herbicides have volunteer barley on the label.”

TAG trials over a number of years have shown that spring-applied sulfonylurea grass weed killers can give valuable control, but that this can be highly variable.

While little or no reliable control was achieved with Atlantis (mesosulfuron-methyl), Monitor (sulfosulfuron) was found to have the best activity against barley volunteers.

“We have also seen good control from Monitor when applied to tackle brome and the many other grass and broad-leaved weeds it is effective against,” Rob Plaice reports.
“At full dose it kills or significantly suppresses barley, causing stunting and preventing viable seed set.

“Later application (GS33-37) is likely to give the highest reduction in seed viability so is advisable for seed and milling wheat producers. But in non-seed crops where the volunteers are already highly competitive I’d always suggest early application as soon as plants get growing.

“Since achieving sufficiently good coverage can be difficult where volunteer barley populations are thick – as many are this season – the label rate of 200 litre/ha water rates should always be used.”

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