Residual Weed Control: Holding the Line

A close-up of green grass growing in the soil on an empty field, with some areas covered by dirt and debris from fall harvests, symbolising the sowing season for winter crops such as winter-wheat. The focus is centered around the lush blades of young grass sprouting out through the thin soil, creating intricate patterns within each patch of dark earth, against a backdrop of flat fields stretching into the distance under a clear blue sky.

November 13, 2025 By Sarah Ferrie, De Sangosse UK

Residual Weed Control: Holding the Line

The mild, open conditions this autumn have encouraged multiple flushes of grassweeds, while warmer soils have accelerated the breakdown of residual herbicides. Even where robust pre- and early post-emergence programmes were applied, a top-up residual may now be warranted to maintain control and protect the crop’s foundation phase.

A portrait of Stuart Sutherland, Technical Business Manager at De Sangosse wearing a navy blue jacket with a white collar and a tie, standing in front of a green field, looking at the camera and smiling, wearing a shirt underneath his jacket. the background is a green, grassy farmland with an overcast sky, in the style of professional photography.

“Residual herbicides are inherently temperature-sensitive,” explains Stuart Sutherland, Technical Business Manager at De Sangosse. “Warm soils drive faster microbial degradation, shortening persistence and allowing new flushes of weeds to emerge. A well-timed top-up ensures sustained control through to dormancy.”

Residual herbicides rely on forming a continuous treated layer across the soil surface. Achieving that uniform coverage can be more difficult in conditions with higher surface trash or actively growing crops that intercept spray droplets.

Illustrative of herbiscide application in fields the photo shows the ground covered with dirt and some green grass sprouts growing in it, which may be young wheat or corn plants just starting to grow. The focus is on one of these seedlings that has not yet grown very much. there seems to have been light snow falling before the picture was taken, as there is still mud visible around some of the seeds. it could also feature small leaves or other debris scattered across the soil surface.

The Target for Residuals

“The target for residuals is always the soil, not the crop canopy,” Stuart emphasises. “You want the herbicide evenly distributed and retained where weeds germinate — not moving down the soil profile where it could affect the seed or emerging roots.”

This is where adjuvant technology plays a critical role.

“The target for residuals is always the soil, not the crop canopy. You want the herbicide evenly distributed and retained where weeds germinate — not moving down the soil profile where it could affect the seed or emerging roots.”
– Stuart Sutherland, Technical Business Manager at De Sangosse

A side-by-side comparison of the same infrared scan with and without an adjuvant, highlighting different distributions through the soil structure. The top panel shows a more clumpy deposition of the herbiscide, while below is one that hes been treated with an adjuvsnt, showcasing how the characteristics of the herbicide spreads evenly through the top layer of the soil. This visual metaphor emphasizes adjuvant's ability to change the efficacy of the product it is combined with.

Without the use of adjuvant technology, striping can occur through the upper soil profile, resulting in loss of residual activity The use of an effective adjuvant will help maintain residual actives in the weed zone for longer.

De Sangosse Residual Ready Adjuvants

De Sangosse’s Residual Ready adjuvants are engineered to:

Reduce drift and improve deposition and soil coverage, ensuring more uniform distribution of active ingredient across the soil surface, even under crop cover or residue.
Enhance retention, keeping the herbicide where it’s intended — in the top 5cm of the soil surface — to control multiple weed flushes and reduce downward movement that risks crop safety.
Optimise droplet size and behaviour, particularly important when using drift-reducing nozzles, which produce coarser droplets that may compromise soil coverage. The adjuvant refines the droplet spectrum to improve contact with the soil while maintaining drift reduction.
Maximise consistency of the herbicide layer, extending the duration of weed control under warm, active soil conditions.

To illustrate that adjuvants for herbiscide are essential rather than optional we show a photograph of an open field at sunrise, with dew on the grass and the sun rising in the background. the camera is positioned near one end of the farm field, capturing both sides of it, showing rows of green wheat sprouts. in front of them lies black soil covered by rye or cover crops like flax. The a calm scene, with no people visible, but for their shadows under the morning light indicates that if you look after your crops right at the start they will grow well and produce high yield.

Final Thoughts

“Adjuvants are often seen as optional, but at this time of year, they’re essential,” Stuart concludes. “They help residuals hit the right target, stay there, and perform consistently — all while protecting the crop itself.”

Get in touch for technical support or advice on our adjuvants.

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