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Welcome to our October update.
This season’s wide variation in oilseed rape growth stages - from well-established, early-drilled crops to those only now emerging after recent rain - presents real challenges for weed control. Targeted management is essential, and this update is focused purely on providing practical solutions to help you tackle weeds effectively in these highly variable conditions.
Oilseed rape crop status and growth
Crops around the country are generally in good condition and are mostly between growth stages 12–18. Recent rainfall has promoted strong growth in both crops and weeds. Encouragingly, there are low levels of cabbage stem flea beetle being reported.
For more information on monitoring this pest and for the top ten CSFB management strategies, you can visit the AHDB website.
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Oilseed rape in Suffolk, photographed on 2 October by our Area Manager, Tom Rouse.
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Weed control and herbicide use
In earlier-drilled crops, initial broadleaf applications should have already been applied. This is a good strategy to ensure weeds do not compete with the crop, allowing it to establish and grow away. This is also important for the control of weeds such as mayweeds, which will have multiple flushes, so a programmed approach is key.
Corteva’s range of OSR herbicides provides flexibility, which is particularly helpful in a season like this, as they can be applied at different times and growth stages to suit the specific conditions.
Where early drilled crops are well-developed and ground cover levels high - it is worth knowing that in trials, where both Belkar® and Astrokerb® have been applied to crops with large canopies, weed control is not compromised.
For later drilled crops you can apply Belkar in tank mix with graminicides for volunteer cereals. Check our tank mix lists for specifics. If applying Belkar – remember you have some flexibility with rates:
- From 1st Sept – end Dec you can apply 0.25L/ha from GS12.
- From 15th Sept and GS16 you can apply more than 0.25L/ha.
- Max rate is 0.5L/ha.
- For more information on weeds controlled by rate see our Belkar Tech Sheet.
- Make sure that at least 90% of the crop is at the relevant growth stage for each dose rate when making an application.
- Please also see our useful OSR Herbicides Programme Topic Sheet.
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Starting to think about propyzamide for blackgrass or ryegrass control?
Here are a few things to remember:
- Propyzamide works best when the soil temperature at 30cm is 10°C and falling, with some soil moisture. This means waiting until the end of October/November in most seasons.
- Trials have shown, using clethodim followed by Astrokerb or Kerb Flo® 500, gives the best control of blackgrass. Ensure propyzamide is applied at the correct time and the right rate for the levels of blackgrass.
- If applying clethodim – remember to leave a 2-week gap before and after application.
- Remember for propyzamide – apply at the Right rate, Right conditions, Right time.
With it being October, now is the time to boost your propyzamide know-how with our Back-to-Basics Knowledge Hub. You'll learn how propyzamide works, how to apply it for optimal results, and get practical advice on responsible use.
Test your knowledge with our quiz to earn 3 BASIS and 3 NRoSO CPD points. Complete the quiz by the end of November 2025 for a chance to win a spot prize!
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Have you downloaded the Corteva Arable App to access Kerb Weather Data?
The Kerb Weather Data (KWD) tool is meant to be used as a guide to local weather conditions to aid growers and advisors in making local tactical decisions to optimise their Astrokerb and Kerb Flo 500 applications and thus their activity against blackgrass.
- Access up-to-date application information for your postcode.
- Pin point your fields to check if conditions are suitable for propyzamide herbicide applications to winter oilseed rape.
- Mitigate against run off by checking the slope of your field.
- An indication of soil type is also built in.
- Manually add water boundaries to individual fields.
- Agronomists can also check postcode information for their farmer clients.
- Increased functionality compared to the Kerb Weather Data web tool.
Search “Corteva Arable” on Google Play or the App Store.
You can also sign up to the Kerb Weather Data for digital newsletters direct to your inbox – these will start later in October.
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Field observations and Corteva hotline key questions answered
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"OSR crops drilled this year without glyphosate pre-drilling may have more difficult and larger weeds to control now in crop. Thistles particularly seem to be in abundance in places; Astrokerb will do a great job on thistles and can often give you control right through to the spring. It’s key to check crops again post Christmas and apply Korvetto® if more thistles have germinated, particularly where LaDiva® may have been used early autumn for thistle control as the aminopyralid persistency at that timing may not last as you’ve been used to from a later autumn applied Astrokerb.
It’s also important to be wary of frosts and cold night temperatures as you plan in your herbicide timings. Any herbicide application ideally needs to be a week away from a frost event so as to not cause excessive stress on the crop."
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"There are a range of growth stages in field depending on drilling date. In a few places some re-drilling has taken place where seed hasn’t come, mainly on headlands. Remember, when applying Belkar or LaDiva, at least 90% of the crop needs to be at GS12."
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"In the midlands crops are variable as drilling conditions remained good throughout August and September. Where crops have been drilled later, time will be short to get the key herbicides on across the next few months. Remember to wait 2 weeks after Centurion® Max applications before applying another herbicide. You then have the option of Belkar (at either 0.25L/ha or 0.5L/ha) for broad-leaved weeds alongside either Astrokerb or Kerb Flo 500. This is a great option where you have problem weeds such as mayweeds, poppy, thistles or groundsel."
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"Since the recent rainfall, both crops and weeds are growing well, prompting the start of applications of either Belkar or LaDiva. The key weeds of concern are cranesbill and mayweed, making both products suitable options. Where applications for broad-leaved weeds haven’t yet gone on, Belkar + Astrokerb is a reliable programme. When applying Belkar, and if dealing with varying growth stages within a field, make sure that you use the rate relevant to the smallest growth stage."
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"As we are seeing more SFI within rotations we are getting questions on unusual and less common weeds in OSR crops e.g. linseed and flaxseed. This has certainly been the case in Scotland. If you are seeing unusual weeds, please get in touch with your local Corteva area manager or our hotline, as we have a raft of data on off-labels weeds."
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Can Belkar be mixed with boron?
Yes, there used to be a label restriction preventing the tank mix but this has now been removed.
Will Belkar control fat hen?
Belkar at 0.5L/ha will control fat hen up to 8cm in size.
What is the best way to control chickweed in my OSR crop?
Belkar at 0.5L/ha will offer moderate control to chickweed up to 8cm in size. This can either be tank-mixed or followed up with an application of propyzamide but control may be reduced if the weed is well established, i.e. beyond 10cm.
Apart from blackgrass what other grass weeds will Kerb Flo 500 control?
Kerb Flo 500 at 1.5L/ha offers moderate control of blackgrass from 2 true leaves to mid tillering. It will also control bent grasses, brome species, meadow grass and ryegrass species.
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Give extra support to your oilseed rape crop by stabilising nitrogen in the Autumn
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A crop reaching its yield potential is underpinned by successful establishment. In oilseed rape we have seen evidence of improved autumn establishment from using Instinct® in the autumn, especially when used in conjunction with slurry and digestate. Our internal development trials showed yield responses of up to 7% and improved spring vigour in oilseed rape when Instinct is used in the autumn.
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Instinct can reduce leaching by around 50% and reduce denitrification through greenhouse gases by 45%. This means nitrogen is kept in the soil for longer and is therefore available for the oilseed rape to use.
The product should be applied at a rate of 1.7L/ha, as close to the application of the source of nitrogen as possible – ideally within a couple of days either side, if not applied with the slurry or digestate. Instinct can be applied to a seed bed and incorporated or simply sprayed on as a surface application.
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Our Pioneer team, local area managers and hotline team are available to answer any questions you may have. To contact us, or to send us an online enquiry, click here.
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Use plant protection products safely. Always read the label and product information before use. For further information including warning phrases and symbols refer to label. ®™ Trademarks Corteva Agriscience Limited and its affiliated companies. All other brand names are trademarks of other manufacturers for which proprietary rights may exist. All manufacturers trade names and trademarks are duly acknowledged. © 2025 Corteva. Belkar® contains halauxifen-methyl (Arylex™ active) and picloram. Astrokerb® contains aminopyralid and propyzamide. Kerb®Flo 500 contains propyzamide. Korvetto® contains clopyralid and halauxifen-methyl (Arylex™ active). LaDiva® contains Arylex™ active, aminopyralid and picloram. Instinct® contains nitrapyrin.
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