Autumn Brings Wide Variation in OSR Crops

A photo of Sarah Hawthorne, Sales and Marketing Manager at DSV, wearing green and black , kneeling in the middle at an angle with her arms around her legs to pose for the photographer. She is sitting between two rows of crops on the ground in a large field in the uk. raw photography.

October 17, 2025 By Sarah Hawthorne & Sarah Ferrie

A Wide Spectrum of Crop Development

This autumn has brought a remarkable range in oilseed rape (OSR) crop development. Across the country, we’re seeing everything from crops drilled in early August now at 7–8 true leaves, to later-drilled crops from mid-to-late September that are only just showing their first true leaf.

“This spread in development really reflects the broader drilling window we’re now seeing,” says Sarah Hawthorne, Sales and Marketing Manager at DSV. “Some growers began sowing at the start of August, while others were still drilling into late September - something made possible by the exceptionally mild and warm conditions this autumn. Driving around, it’s clear there’s significantly more OSR in the ground this year, and in many cases, crops are looking stronger than we’ve seen for several seasons.”

The ground is covered with crops, which have just sprouted and show the leaves of these plants in their early stages of growth in a lush and verdent green. The field seems to stretch out as far as one can see. In some places, there may even be patches of cultivated rich brown soil between them. Photorealistic, shot on a canon eos r5.

Strong Crops Moving Quickly – PGRs Recommended

Many earlier-drilled crops are racing ahead, prompting timely consideration of plant-growth regulators (PGRs) to manage growth and build resilience.

“For forward crops, an autumn PGR can really help balance canopy structure and root-to-shoot growth,” Sarah explains. “The benefits include encouraging strong root development, improving tolerance to wet or dry conditions over winter, and increasing root collar diameter – which in turn helps the crop tolerate cabbage stem flea beetle (CSFB) larvae. PGRs also keep the growing point close to the ground, protecting developing buds from weather exposure.”

She adds that PGR applications can also be a good opportunity to include boron, which supports root development, nutrient movement, and cell wall strength – all essential for building a robust crop ahead of winter.

The Flea Beetle, a black and gold beetle on green leaf with white spots, macro photography, macro lens, macro photo of an insect in nature, macro view of a bug on a plant. The menacing black and yellow bug is sitting on a round leaf with a dark background.

Flea Beetle Pressures Emerging Again

Unfortunately, flea beetle activity returned in late September bringing renewed challenges - particularly for later or slower-developing crops.

“We’ve seen the worst damage where split fields or staggered drilling dates have created uneven crop stages next to each other. “Beetles appeared to have migrated from stronger plants into smaller, more vulnerable ones. Even where early drilling moisture supported good establishment, smaller crops remain at risk and should be monitored closely.”

A close-up of a broad leaf with small white spots on it, which is a sign that phoma can spread and damage crops. This picture would be very interesting as it does highlight plant health showing the trouble with fungus. The photo is very high resolution, suitable for printing at large sizes. We feature the leaf in focus, very sharp at the area showing the phoma spot, but shallow depth of field due to the nature of macro photography.

Phoma Making an Early Appearance

Phoma leaf spot is also appearing earlier than expected in some varieties, particularly those with only a single resistance mechanism. Sarah advises close monitoring: “Where thresholds are met, a timely fungicide can protect leaf tissue and help maintain steady autumn growth.”

A photo of the front view of Rob Suckling, Commercial Technical Manager at De Sangosse. He is also an experienced generational english farmer himself. Rob is in his thirties wearing a navy blue t-shirt and black trousers with stylish tan farm boots, crouching on top of a dirt patch in a farm field that is currently in the stubble state, ready for soil cultivation, where grassweed control is critical. He is looking at the camera. The sky above him has grey clouds. It is the autumn season. There are trees behind him. In the background, there are green grass fields. The photo was taken using a canon eos r5 mirrorless camera.

Grassweed Control – Timing and Water Quality Are Key

Following the recent rainfall and mild temperatures, many OSR fields have seen a flush of grassweeds, adding complexity to autumn management - especially where crop growth stages vary significantly within the same field.

“In some fields, you can find plants at one true leaf right next to others at six true leaves,” explains Rob Suckling, Commercial Technical Manager at De Sangosse.

That has been making clethodim timing particularly challenging but getting it right is crucial for performance and stewardship.

“Clethodim should not be applied after 15th October or to crops with more than 6 true leaves, in-line with stewardship measures. For best results, Rob advises applications in at least 150 L/ha of water, using a steady forward speed, and always use a true water conditioner that includes pH buffering - such as X-Change.

“Like many herbicides, clethodim is a weak acid and susceptible to lock-up by hard water cations such as calcium and magnesium,” Rob explains. “X-Change sequesters these ions and buffers the spray solution to around pH 4.5-5.0, which keeps clethodim fully active and improves uptake. It’s one of the simplest and most effective ways to safeguard herbicide efficacy.”

Follow-up propyzamide applications should then be applied at least 10-14 days after clethodim, once soil temperatures have cooled sufficiently to ensure maximum residual activity.

Learn more about managing herbicide performance and water quality in our Clean Water. Clean Kill. glyphosate stewardship hub.

Visit the Hub

Autumn blackgrass in winter oilseed rape, this close-up is showing a lack of broadleaf weed control, the leaves and grass under agricultural plants, indicate signs of translucence with water droplets. The picture of green leaves growing on the ground with water droplets on them also shows the background, soil is grassy. This is less than ideal, agriculturally speaking. The fact that the close-up photo of green leaves and grass with water droplets on them, features ground which is covered in lush green underbrush will present a problem. The crop will have to compete. Clethodim could have been neutralised by hard water, which would cause this problem.

Broadleaf Weed Control – Don’t Let Hard Water Undermine Performance

At the post-emergence timing, keeping broadleaf weeds in check is key to prevent moisture and nutrient losses to establishing oilseed rape crops.

For optimal efficacy, it is important to be aware that it is not just clethodim that is susceptible to hard water efficacy loss – other systemic herbicides can also be compromised too. “Rob notes that the efficacy of products containing synthetic auxins, such as picloram, aminopyralid and halauxifen-methyl can be improved by conditioning the water with X-Change.

“Hard water cations like Ca2+ and Mg2+ bind with weak acid herbicides, forming insoluble salts that reduce uptake,” he says. “Correcting water hardness means the active ingredient stays in its most biologically available form. That’s particularly valuable when targeting weeds that are only moderately susceptible where every bit of performance matters.”

X-Change adds Valuable Efficacy to Belkar in Hard Water Areas

Summary of 3 trials showing the effects of X-Change on Belkar mayweed control in hard water – 3 different rates

Belkar

Belkar + X-Change

Mayweed Control (%)

N=3 trials conducted 2017-2020 – 2 trials by Cropsure, 1 trial by Green Bank Agriculture. Applications made at 4TL of the mayweed in 150 L/ha water volume. Hard water used >350ppm calcium carbonate. X-Change applied at a rate of 0.25% or 0.3% according to the water hardness in each trial.

Correcting water hardness means the active ingredient stays in its most biologically available form. That’s particularly valuable when targeting weeds that are only moderately susceptible where every bit of performance matters.
– Rob Suckling, Commercial Technical Manager at De Sangosse

Here a small patch of crop sprouts emerging from the dirt in an agricultural field. But the framing of the image is zoomed right in on the plant and the seedlings competing. In terms of agricultural phase, some leaves have not yet opened and still look like buds on top of the ground, while others show their greenery. The soil is mixed with straw and organic waste in th cultivation process and has visible cracks.

Early Drilled Crops – Consider an Autumn Nitrogen Top-Up

According to Sarah, forward, early drilled crops are also using up available soil nitrogen more rapidly than expected.

“In some situations, an autumn nitrogen application of around 30 kg N/ha could be justified,” she explains. “Warmer autumns allow plants to continue taking up nitrogen, which can help maintain biomass and aid recovery from late-season flea beetle or pigeon damage.”

As always, she advises considering previous cropping, soil nitrogen levels, and environmental guidelines before applying.

This image features a large field of agricultural plants showing foliage spots and patches with brown, curled leaves, with some weed control positive areas and negative areas too, visible in the background. The ground is covered by lush, green leafy cannabis plants. There is no direct sunlight, highlighting spot-like areas and gaps. In summary a field of lush, dark green leafy greens, viewed from above. The majority of the field is covered in vibrant green leaves, with a small patch in the middle displaying some yellowing and brown spots.

Improving Phosphate Use Efficiency – The Role of Soil Nutrient Activators

While phosphate remains a cornerstone of OSR establishment, it’s one of the nutrients most easily locked up in the soil. Both high pH (alkaline) and acidic conditions can make phosphate unavailable to plants – either by binding it with calcium in alkaline soils or with iron and aluminium in acidic ones.

“Even where soil indices suggest sufficient phosphate – soil index of 2‑5 - availability can be the limiting factor,” explains Rob. “That’s where soil nutrient activators come in. They work biologically and chemically to keep phosphate and key micros soluble and accessible for longer – particularly beneficial in late-drilled or slow-growing crops.

“These products can make a real economic difference where phosphate efficiency is restricted by soil chemistry,” Rob adds. “They’re about improving what you already have in the soil, helping roots access phosphate more effectively and building stronger establishment in challenging conditions.”

Finishing Autumn Strong

Whether crops are racing ahead or still establishing, the next few weeks will set the tone for winter resilience and spring recovery.

“Across all scenarios, attention to rooting, nutrition and water quality can make a real difference,” says Sarah. “We’ve seen a lot of variability this season, but the fundamentals remain the same – build strong roots, protect leaves, and keep the plant balanced.”

Rob agrees: “By combining good stewardship with technologies that protect chemistry and nutrients, growers can safeguard performance and consistency in a very unpredictable season.”

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