Growers have new options available for weed control in cereals this autumn. Proclus (aclonifen) and Alternator Met & Octavian Met (metribuzin + flufenacet + diflufenican) all provide an improvement in black-grass control. Here are some key points to remember about the new products:
Only available in a co-pack to mix with Liberator (flufenacet + diflufenican). A three-way co-formulation is planned for future seasons but this year the only way to see how aclonifen enhances Liberator is to mix on farm. “The plan is to have a co-form available in future seasons, but we are awaiting regulatory approval which can take time. The big benefit of the co-form is ease-of-use. Farmers tank-mixing Proclus and Liberator still get the same uplift in control,” says Bayer’s Craig Simpson.
Trials results show an average 10-15% improvement in black-grass control by adding Proclus compared to straight Liberator. Brome has a similar improvement with rye-grass slightly lower at 5-10%. “As well as the improvement in control, we are also seeing less variability in results when Proclus is added” says Mr Simpson. “Many farmers already mix additional actives with Liberator at pre-em to boost control. But the improvement and reliability of Proclus make it a strong contender to be the mix partner of choice.”
Aclonifen is shoot acting, it creates a film on the soil surface and is absorbed by weeds as they emerge through the soil. “The activity of aclonifen complements the root activity of flufenacet to attack weeds. One possible reason for the reduced variability in results is that this shoot activity is not as dependent on soil moisture as flufenacet.”
Proclus is a more specialised herbicide than straight Liberator. It can only be used at the true pre-em timing and only in winter wheat. For growers looking for a more flexible herbicide Alternator Met and Octavian Met may be a better option.
Aclonifen has a longer half-life than most pre-em actives so it provides good residual protection. As part of a Bayer sponsored MSc project, Mr Simpson looked at residual activity of herbicides. The project demonstrated that aclonifen’s persistency does help to control black-grass throughout autumn and into winter.
Aclonifen is in a completely different active group to other common pre-em herbicides and is inherently considered to have a low resistance risk. “Last year, we learnt that there is some reduced sensitivity to flufenacet in black-grass and rye-grass so having a new mode of action to support flufenacet is essential for resistance management.”
Both products can be applied at the full 1l/ha rate until the end of September and at 0.5 l/ha until the end of November. “The full rate is probably for early drilled crops, particularly barley where it gives a good control in one can without any mixing required,” says Mr Simpson. “The 0.5 l/ha rate is most likely to be used for residual top ups later in the autumn.”
At the full rate it controls more black-grass than Liberator. It also improves brome control and broad-leaved weeds including groundsel and cranesbill.
Metribuzin is primarily root acting like flufenacet but there is also some foliar uptake which may be particularly helpful for residual top ups. “Residual top-ups have become more common in recent seasons especially as post-emergence sprays have become less popular. This additional activity at the top up could be very valuable and we anticipate that this is the timing where these products will come into their own.”
Metribuzin is in a unique group of actives for cereal weed control so it is valuable for resistance management, particularly protecting the long-term efficacy of Liberator.
Understanding your seedbank is an important step in gaining a critical advantage on black-grass control this season.
Black-grass control does not start with the pre-emergence herbicide programme. Doing everything possible to reduce the weed population before you drill the crop is key, and it means making good management decisions right from the off.