Agronomy advice for Scottish growers this summer

1) Protective head sprays keep crops greener for longer 

The dry weather is bringing crops forward and most flag leaf sprays will likely have been sprayed in the last two weeks of May.  

There’s still a long way to go before harvest and, if it hasn’t already, it will rain at some point. If you have a decent looking crop, you will want the ears protected when it does rain, while if it remains dry sprays will be 100% protectant, which will help get the most out of fungicides.  

Options for T3 sprays depend a little on what has already been sprayed in the programme. If you haven’t used your two applications of fungicides containing strobilurins or two applications of SDHI fungicides, either could be options.  

Both SDHIs and strobilurins will provide additional physiological benefits on top of disease control. Aviator® Xpro® or Ascra® Xpro®, for example, help alleviate drought and heat stress to keep the crop greener for longer.  

Timing, particularly for Fusarium control, should be mid-flowering so when you see anthers coming out of the ear about halfway down then the time is perfect. But keep a close eye on crops because that lasts for about two days and is very easy to miss.  

Brown rust is less of an issue in Scotland than further south, but mildew can be a problem as well as Fusarium, Microdochium and Septoria, especially on lighter land in northern Scotland. That can easily jump up the plant, which is where prothioconazole and spiroxamine come in handy. 

2) Finish spring barley disease control programmes 

Early drilled spring barley crops aren’t looking too bad considering the dry conditions, but later drilled ones have struggled a bit.  

A lot of growers have used reduced doses of fungicides at T1, which will need topping up as awns emerge. Perhaps surprisingly, there is a bit of Rhynchosporium kicking about, especially in min-tilled crops after a previous barley. Any rain will splash that up plants. 

And with feed barley prices lacklustre, it will be important to attain malting barley quality to qualify for premiums, which a decent T2 will help to achieve.  

Products like Siltra® Xpro® and Ascra® Xpro® will give good foliar disease control, while also helping with greening and drought stress. 

3) Assess timing carefully for oilseed rape desiccation 

Most oilseed rape crops in Scotland are now desiccated before harvest with Roundup®. Obviously, timing is crucial to ensure seeds are not red at harvest that can lead to rejections. Spraying too early will also impact yield and oil content and therefore lead to smaller oil bonuses.  

To do a quick assessment, go into the crop, find a branch halfway down, open some pods and if the seeds are brown, do a proper assessment where you take 20 pods that are representative of the field, and check whether at least two-thirds of the seeds in at least 15 pods have changed colour from green to brown.  

If seeds are still green, come back in a few days’ time to re-assess.  

4) Sample next year’s oilseed rape fields for clubroot 

There’s much less debate in Scotland about whether to grow oilseed rape – it’s a good break crop that is performing as expected.  

If you think next year’s fields might have clubroot, get them sampled as soon as possible as it takes some time for results to come back.  

Where soil tests show clubroot, DK Pledge has a good agronomic profile, including markedly less seed shedding in the run up to harvest than the current clubroot resistant variety.  

Also keep an eye out for the currently coded new clubroot resistant AHDB Recommended List candidate variety DMH585 if you visit trials this summer. It has turnip yellows virus resistance, alongside pod shatter and Phoma resistance. Light leaf spot is a slight weakness but is easier to manage than clubroot. 

Another candidate variety that looks excellent for the north is CWH596. It doesn’t have clubroot resistance but has particularly rapid growth in the autumn and earlier regrowth in the spring. It also has triple Phoma resistance using both Rlm7 and RlmS genetics.  

Other varieties that could be suitable where clubroot resistance isn’t required include DK Extremus, which is also particularly rapid in autumn and quick to regrow in spring. It also has excellent standing power and demonstrated Verticillium wilt tolerance in ADAS trials.   

The turnip yellow virus resistant DK Excentric is a flexible driller, meaning it can be drilled from late July through to mid-September. It’s a bit slower in the autumn than DK Extremus but shows good vigour and disease resistance. 

All DEKALB® varieties are available with the Bayer Establishment Scheme again.  

5) Alternate modes of action in blight programmes 

With an early start to late blight control programmes, constructing a programme carefully that alternates modes of action and complies with guidance on not using too many applications from one family of chemicals is both harder and important.  

For example, with carboxylic acid amides (CAA) fungicides, such as Revus®, the guidance is not to use them in more than 50% of the applications in the programme, or more than two consecutively.  

Likewise, OSBPI-containing fungicide, like Zorvec Enicade® shouldn’t be used more than three times in a season if the number of sprays in the programme is more than 10, and only twice if the programme will be between six and 10 applications. There are also restrictions on QiI active ingredients, which include Ranman® and Shinkon®, so it becomes quite complicated to construct a programme that complies with all of those requirements.  

Infinito® fits well as an alternative mode of action that can be used through the programme. It has excellent activity on zoospores that cause tuber blight, so it’s worth keeping one or two of your four available applications for the end of the season. The remaining applications can be used earlier in the programme from full canopy for foliar blight control, providing an alternative mode of control. 

6) Watch out for early blight 

Alongside late blight keep monitoring for early blight. It could well become a bigger issue with loss of mancozeb, which provided incidental control when used as part of late blight fungicide programmes.  

Without mancozeb, Alternaria, which causes early blight, might need a specific fungicide in addition to the late blight programme. EuroBlight trials have shown that Caligula® is the strongest product available for early blight control.  

Used at 0.5 L/ha, it can be used three times in total in a season, but in no more than two consecutive applications. 

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 Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Aviator® Xpro® contains bixafen and prothioconazole. Caligula® contains fluopyram and prothioconazole. Infinito® contains fluopicolide and propamocarb. Ranman® contains cyazofamid. Revus® contains mandipropamid. Roundup® contains glyphosate. Shinkon® contains amisulbron. Siltra® Xpro® contains bixafen and prothioconazole. Zorvec Enicade® contains oxathiapiprolin. Ascra®, Aviator®, Caligula®, DEKALB®, Infinito®, Roundup®, Siltra® and Xpro® are registered Trademarks of Bayer. All other brand names used are Trademarks of other manufacturers in which proprietary rights may exist. Use plant protection products safely. Always read the label and product information before use. Pay attention to the risk indications and follow the safety precautions on the label. For further information, including contact details, visit www.cropscience.bayer.co.uk or call 0808 1969522. © Bayer CropScience Limited 2025