Advice for ear sprays, oilseed rape variety choice and controlling potato diseases for western growers

1) Changeable June weather would mean greater spend at T3 

It seems many growers and agronomists are planning to cut back to an SDHI-free flag leaf fungicide spray. 

That means if you get a period of changeable weather into June it could be where using a SDHI fungicide, such as Ascra® Xpro® at T3 is a good fit as it will cover off rusts, Septoria and with the prothioconazole will protect against Fusarium.  

If it remains mostly dry and growers are aiming to keep costs low, then prothioconazole plus tebuconazole is a good option that will keep rust down to eke out as much yield as we can. Most varieties are fairly susceptible to brown rust, and with its fast cycling can come into crops very quickly. 

Products containing a strobilurin fungicide, such as Zephyr®, will also help against rusts and provide some physiological benefits, while the same applies with the SDHIs in Ascra® Xpro® and Aviator® Xpro®. These provide physiological benefits in terms of heat stress, nitrogen scavenging and stem strengthening, meaning dry weather doesn’t necessarily equate to lower return from using higher value fungicides.  

2) Timing advice for pre-harvest glyphosate 

Timing, as every season, is the key to getting the best result if you decide to use Roundup® to desiccate oilseed rape crops. It needs some planning to make sure you allow sufficient time for the crop to dry down ahead of harvest and to adhere to harvest intervals to make sure residues don’t exceed limits. Good timing will also help with weed suppression.  

There’s full guidance on our website, but for oilseed rape make sure you take a representative sample of the growth stages in the field as a whole. Aim for around 20 pods – the crop will be ready for spraying when at least two-thirds of the seeds in at least 75% of pods have turned from green to brown.  

If you go too early, not only can you reduce yield and oil content, but also increase the incidence of red seeds, which can lead to rejection from the crushers. 

3) Tools and traits that help if you’re drilling oilseed rape in the later window 

Growers seem to have got on reasonably well in the southwest where they are growing oilseed rape. With weather typically staying warmer for longer in this part of the country, that potentially helps with those choosing to drill in September after the main cabbage stem flea beetle migration has peaked. Our MagicTrap tool is useful to help monitor for that peak.  

If you are drilling in September rapid autumn growth is perhaps top of the list of varietal traits to look for, along with decent disease resistance so growth isn’t inhibited.  

Most of the DK varieties are flexible enough to be drilled either in the early August or later September windows. DK Extremus, for example, is one that fits the later window particularly well as it exhibits rapid autumn growth and has a good disease resistance profile. One of its real strengths is how fast it gets away in the spring, which is useful to grow away from any larval damage.  

DK Excentric is slower in the spring, but offers a very flexible drilling window, which is helpful for growers who are looking to time drilling with when there are good moisture levels in the soil. It has TuYV resistance and in independent trials has matched Limagrain varieties, such as Ambassador and Aurelia.  

4) Could early blight be more of a threat in potatoes? 

Early blight hasn’t historically been a big problem in the southwest, but the current dry weather combined with irrigation could mean it’s more of a threat this year as Alternaria development is favoured by alternate dry and wet periods.  

The second factor that might change the threat level is that mancozeb is no longer available to buy, so any growers without sufficient stocks in stores won’t benefit from the incidental control it gives when used in late blight programmes.  

Where varieties are susceptible, Markies being the most obvious candidate, it could be worth planning a dose of a specific fungicide for controlling early blight, particularly where mancozeb isn’t available, at an appropriate time in the programme.  

According to the EuroBlight table, the best efficacy comes from Caligula® but remember it doesn’t control late blight so needs to be an addition to late blight programmes. 

5) Next season’s weed control starts now 

This month is when you really start to see the results of weed control programmes. Most grassweed control this season seems to have been decent, at least autumn residual herbicides seemed to have worked well. But where there are patches or fields with very poor control, a zero-tolerance approach would be to spray them out with Roundup®.  

Around or just after flowering is the ideal time to hit grassweeds with glyphosate as it will be carried down into the roots to give a better level of kill. Use at least 1080g/ha of glyphosate to ensure you don’t have any survivors.  

If fields don’t warrant spraying off, which hopefully is the vast majority, then mapping fields to record and monitor weed populations is a good start for planning next season’s weed control. That can be done with a range of digital tools. 

If mapping or visual observations show problem areas, think about how to tackle these. Do you need to change cropping in a field, for example? If you have a bad brome infestation, maybe winter barley isn’t the best option. And what cultivations might be most appropriate post-harvest for particular weeds? 

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Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Aviator® Xpro® contains bixafen and prothioconazole. Caligula® contains fluopyram and prothioconazole. Roundup® contains glyphosate. Zephyr® contains prothioconazole and trifloxystrobin. 

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