Options opened up for grass-weed control

Control of complex grass-weed populations remains a priority in cereal crops but new herbicide options are helping to ease the challenges, believes Martin Dear of The Agronomy Partnership.

Difficult black-grass and rye-grass situations consistently demand robust control strategies and the problem is compounded when brome species are found within mixed grass weed populations.

"Patches of brome alongside other grass-weeds have become more common," Mr Dear observes, "So new herbicide Pacifica (mesosulfuron-methyl + iodosulfuron-methyl) has been welcomed by growers planning programmes aimed at these specific, brome-led populations.

"Previously in such complex situations, programmes were limited," he continues. "Although Atlantis (mesosulfuron-methyl + iodosulfuron-methyl) is the preferred choice for black-grass and rye-grass control, the restrictions on sulfonylurea product sequences leave growers without effective options for brome control," Mr Dear explains.

"An obvious illustration is where you've already had to use Atlantis to bring other grass-weeds in check but then cannot use Attribut® (propoxycarbazone-sodium) against brome species," he points out. "Both are sulfonylurea-based products which cannot be used within the same season.

"But, if Pacifica lives up to its claims, it will prove ideal for tackling complex weed mixes. It enables us to plan economical and effective control programmes for all grass weeds, including the bromes, without compromising best practice through an unapproved sequence," he continues.

"Several Pacifica users began the autumn programme with a well-timed residual pre-em treatment of reduced rate Trooper® (pendimethalin + flufenacet), but in my experience using a full rate does give slightly better grass weed control."

Mr Dear adds that if brome is not an issue then Atlantis remains the most appropriate option for targeting black-grass and rye-grass.

"Just remember, when applying Pacifica or Atlantis it is essential that growers stick to best practice guidelines to get optimum efficacy and avoid the onset of resistance."

While it is important to target all grass-weeds as early as possible to reduce competition with the crop, growers must ensure that all plants are in active growth, which can mean waiting 2-3 days after a prolonged cold period.