Optimising Residual Herbicide Efficacy in Early & Late Drilled Wheat

Photo of Rob Suckling, Commercial Technical Manager at De Sangosse, a man of age between 30 and 45 years old with short hair in blue t-shirt with small logo on it written De Sangosse. Rob is looking at the camera. The blurred background is of countryside landscape, cloudy sky, professional photography, good quality. Rob looks confident and trustworthy. DeSangosse News Article Image
October 12, 2025 Sarah Ferrie 06 Comments

Optimising Residual Herbicide Efficacy in Early & Late Drilled Wheat

Mild, open autumn conditions have given growers one of the best drilling windows in recent years. Many winter wheat crops are already well established, but with soils still warm and moist, weed germination remains active across much of the country.

According to Rob Suckling, Commercial Technical Manager at De Sangosse UK, that combination makes this season a critical test for residual herbicide performance and timing.

“We’ve had a brilliant start,” says Rob. “But the same conditions that helped crops get away quickly are also perfect for blackgrass and ryegrass to keep emerging. Getting the best from your residual herbicides depends on matching application strategy to drilling date and soil conditions.”

close-up of green wheat sprouts growing in the dirt, with a focus on each individual blade of wheat and the surrounding soil. This is macro photography of fresh wheat seedlings and black soil background. this is an agricultural farm with grain crops for commercial UK agricultural production, a blurred background of nature. DeSangosse News Article Image

Early Drilled Wheat: Great Start, Persistent Risk

Early-drilled crops (late September–early October) are generally at two- to three-leaf stage, and looking well. While early establishment reduces some weed competition, these crops also face longer exposure to successive germination waves.

“Residual herbicides applied around drilling have worked well, but their persistence is finite,” Rob explains. “Warm soils increase microbial activity, and actives can degrade faster than expected. That means follow-up residuals often have a valuable role, even where the field looks clean from a distance.”

The hand of an agromomy expert is pointing at the soil where it was planting wheat seeds. A close-up of some small green wheat sprouts growing from underground is shown in this real, high-resolution photograph. With the hand pointing at the soil where grass seed has just been sown, this is illustrating a discussion of how to plant and the typical growth challenges for wheat seeds on a UK farm, captured through hyper-realistic photography in a close-up shot using a dslr canon camera. DeSangosse News Article Image

Key considerations for early-drilled wheat:

  • Monitor for new flushes: Warm, moist topsoil can trigger fresh weed germination after rain. Walk fields — especially tramlines, shaded patches and compacted zones.
  • Don’t delay a follow-up: Residual protection typically declines after 4–6 weeks in mild conditions. Reapplying before germination peaks helps extend control into late autumn.
  • Use adjuvant support: A compatible adjuvant can improve distribution and binding of residual actives in the top 5 cm, maintaining an even herbicide layer and slowing degradation.

“Think of adjuvants as insurance,” Rob adds. “They don’t replace chemistry — they help it work harder for longer, especially when conditions accelerate breakdown.”

Think of adjuvants as insurance, they don’t replace chemistry — they help it work harder for longer, especially when conditions accelerate breakdown.
– Rob Suckling, Commercial Technical Manager at De Sangosse
The photo shows an empty field with the seedlings of wheat sprouting in some places, which is illustrating where wheat drilling has been delayed as the ground has been plowed and filled up with organic matter. In parts, you can see straw scattered across it. It is a cloudy day with gray clouds overhead. The photo is taken from ground level. DeSangosse News Article Image

Late Drilled Wheat: Compressing the Weed Window

Where wheat drilling has been delayed — following root crops, maize, or to manage grassweed pressure — conditions are typically cooler and wetter, but still conducive to germination. Weed flushes tend to be more concentrated, and timing residual applications correctly becomes even more critical.

“Later drilling often gives a cleaner start, but the window for effective residual activity is much shorter,” Rob explains. “You need consistent coverage across the seedbed, and moisture to activate actives quickly.”

THis image shows a Fendt tractor pulling a soil cultivator in an agricultural field, with a farm and farmland background. The bright vibrant colours of the red wheeled and green body tractor are indicative of commercial photography. The background shows rolling hills and fields of crops in autumn. in front, you can see an empty field where everything will be sown next year. it is a dusty behind where the cultivator has churned the soil and dust particles float above the ground. DeSangosse News Article Image

Key considerations for late-drilled wheat:

  • Ensure good seedbed preparation: Fine, consolidated seedbeds give the best soil contact for residuals. Avoid cloddy or trashy surfaces that allow uneven coverage or herbicide loss.
  • Target soil moisture, not rainfall: Apply when soils are moist but not saturated — heavy rain soon after application can move actives below the germination zone.
  • Choose adjuvants that aid retention: In wetter, cooler soils, adjuvants help stabilise the herbicide layer in the top few centimetres and reduce leaching.

“Residual efficacy depends on keeping actives where weeds germinate — in that top 5 cm zone,” says Rob. “That’s the layer we’re protecting with both the right technique and the right support products, such as De Sangosse’s Velomax, Byte or Deploy adjuvants.”

A tractor with a sprayer is spraying large fields, lack of crops would indicate the application of pre-emergence herbicide, in the style of aerial photography, with a panoramic view and a wide-angle lens. This drone photo of a tractor spraying farmland, with green and yellow fields under a bright blue sky. aerial photography, high-resolution photograph captured with a canon eos r5 camera and an ultra-wide-angle lens, providing an aerial view at 20mm f4. A hard working farmer in the middle of an empty field with brown soil is driving a green and yellow john deere with the sprayer working on it. DeSangosse News Article Image

Practical Tips to Maximise Residual Performance

Rob’s recommendations for optimising residual herbicide efficacy this autumn:

  1. Prioritise seedbed quality
    Residuals rely on consistent soil coverage. Well-consolidated, moist, fine seedbeds reduce gaps and ensure even distribution.
  2. Calibrate carefully
    Check boom height, forward speed and nozzle pattern. Maintain uniform coverage across the full width — patchy application equals patchy weed control.
  3. Time applications for active weed flushes
    Residuals are most effective when weeds are germinating. Apply before or during predicted emergence periods, not after visible growth.
  4. Include an adjuvant where appropriate
    “Adjuvants such as De Sangosse’s residual-supporting products can enhance retention and persistence in the weed germination zone,” Rob notes. “It’s about optimising the chemistry already in the tank — not adding cost, but adding confidence.”
  5. Ensure correct mixing order
    Mix adjuvants in the correct sequence for stability and efficacy.

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Residual Ready Thinking

“Whether you drilled early or late, this season is about keeping control consistent,” Rob concludes.

“Residual herbicides remain our most powerful tool against grassweeds alongside cultural controls — but they only perform at their best when the basics are right. If you maintain a good seedbed, choose the right timing and support your chemistry with the right adjuvant, you’ll carry that clean start through to the spring.”