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Weed Management

Bayer Crop Science

Actives for Autumn: Choosing Effective Herbicides for Cereal Weed Control

Article overview

There are many herbicides for farmers to choose from when planning autumn weed control in cereals. The best option will vary from farm-to-farm but the principles behind the choice don’t change. Here are some important things to consider when choosing actives for autumn.

Current practice

The recent Bayer Mode of Action Survey 2023 showed that farmers typically use 3–4 modes of action for weed control in wheat across the pre-em and post-em programme (See Chart 1). But it’s important to remember that some of most important actives are in the same Herbicide Resistance Action Committee (HRAC) groups.

Chart 1: Number of Modes of Action Used in Typical Wheat Weed Control Programme (Excluding Glyphosate Pre-Drilling)

Group 15 includes flufenacet, tri-allate, prosulfocarb and ethofumesate; Group 12 has picolinafen and diflufenican; and most post-em chemistry for grass-weeds and broad-leaved weeds is Group 1 or 2. Another question in the survey asked which actives farmers used over the last three seasons. The most used actives were glyphosate, flufenacet, pendimethalin and diflufenican (see Chart 2).

“The breakdown of which actives farmers are using doesn’t contain any great surprises, but it does highlight some risks and opportunities,” says Bayer’s Tom Chillcott. “Most obvious is Group 15, all those four actives still have a lot to offer and from an efficacy standpoint can complement each other well. But using them in the same programme isn’t sound resistance management. Make sure there are other modes of action alongside Group 15 actives in the program.”

“Metribuzin is an opportunity it’s the only HRAC Group 5 available in cereals. It’s sold as Alternator Met and Octavian Met in a co-form with flufenacet + diflufenican. But has been a niche product since launch mainly because of the label. That’s changed this year and the full 1 litre rate can now be used throughout autumn.”

“The new chemistry, aclonifen and cinmethylin, is both an opportunity and a risk. Our trials show that both can give a step up to the herbicide programme. But a new active isn’t an excuse to ease up cultural controls or rotating actives, our aim has to be to keep all this chemistry effective for as long as possible.”

Chart 2: Actives Used Over the Last 3 Seasons (Number of Users)

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