Trials show the inclusion of pendimethalin can boost weed control by 10 to 16% when added to an aclonifen, flufenacet and diflufenican based herbicide programme.

With the window for winter wheat drilling rapidly approaching, growers need to plan carefully to maximise weed control. That is according to ADAMA’s herbicide technical specialist, Holly Pratt, who explains that recent trials have proven the value of including additional active ingredients to some of the more commonly adopted herbicide programmes.

“After a lacklustre year for many growers and their crops, the focus on input expenditure will undoubtedly be magnified as we enter a new cropping cycle,” Holly explains. “Whilst pressure on cashflow might tempt some growers to cut back on crop protection, that would be a backwards step in terms of weed control as any infestations that go unchecked in the autumn will have significant repercussions in terms of crop yield and quality next summer.

“That said, we appreciate the need to ensure any inputs are justified in terms of their return on investment, so we’ve been carrying out a series of trials to determine exactly how and when the investment in herbicides should be made.”

In trials which tested the impact of adding ANTHEM (400g/l pendimethalin) to a boxset of Proclus^® (aclonifen) plus Liberator^® (flufenacet & diflufenican), it was found that the addition of pendimethalin significantly improved black-grass control. In fact, six of eight independent trials (including work carried out by ADAS and NIAB) have shown that adding ANTHEM can improve black-grass control by between 10 and 16%. The inclusion of pendimethalin was also seen to reduce the variability of black-grass control.

Additional observations showed that the four-way tank mix of aclonifen, flufenacet, diflufenican and pendimethalin resulted in no obvious signs of phytotoxicity to the crop.

“However, it was noted that drilling depth can affect crop vigour,” Holly adds. “It is therefore vital to adhere to the drilling depth guidance for the herbicides being used. For example, where Proclus and/or ANTHEM are being used, the recommendation is for seed to be covered by a minimum of 32mm of settled soil”.

Holly continues to explain that while the accepted best practice when it comes to tackling difficult weeds such as black-grass, ryegrass and brome is to delay drilling until well into October, it is likely that many growers will instead opt to drill new crops of winter wheat as soon as possible – predominantly to avoid the potential for the arrival of wet weather hampering field operations.

“Where early drilling is the preferred strategy, growers are advised to implement a strong stack and sequence of herbicides to ensure adequate weed control is achieved not just during the crop establishment phase, but also to provide a longevity of protection as the crop develops,” Holly says.

“New active ingredients such as aclonifen and cinmethylin will be essential to prevent black-grass and ryegrass from stealing a march on early drilled crops. However, despite their improved efficacy, even these new herbicides will require additional help to maintain weed control further into the crop’s development.”

Growers are therefore advised to ‘power-up’ their herbicide programmes by incorporating additional active ingredients from different mode of action groups, with diflufenican, pendimethalin and chlorotoluron all providing additional, cost-effective weed control options.

 “For example, a programme which starts with a foundation application of aclonifen, diflufenican and flufenacet at the pre-emergence timing can be enhanced by the addition of ANTHEM (400 g/l pendimethalin) at the same timing, or by a post-emergence treatment of TOWER (250 g/l chlorotoluron, 40 g/l diflufenican & 300 g/l pendimethalin),” Holly explains.

“Similarly, where a foundation application of cinmethylin and pendimethalin is being used, the addition of HURRICANE (500 g/l diflufenican) will help to boost the pre-emergence treatment. This could then be followed by a post-emergence application of TOWER or OMAHA 2 (40 g/l diflufenican & 400 g/l pendimethalin) to extend the window of weed control.”

CHROME (280 g/l chlorotoluron + 40 g/l diflufenican + 80 g/l flufenacet) can also be used where diflufenican hasn’t been applied at the pre-emergence timing, or if sufficient pendimethalin has already been applied.

“For the most difficult grassweeds, our experience suggests that reduced rates of flufenacet or prosulfocarb can be beneficial against black-grass and ryegrass respectively when included in an early post-emergence sequence,” Holly concludes. “In these situations, a black-grass programme may include TOWER or OMAHA 2 plus flufenacet at the post-emergence timing, or TOWER plus prosulfocarb where ryegrass is being targeted.”