How to manage crops during April in the west

Take out rust infections before T1

Quite a lot of the top 10 winter wheat varieties in the ground this season have poor, or at best, only moderate resistance to brown rust. Last year we saw a lot of brown rust because of the mild winter weather, so there will likely be a decent amount of inoculum carried over, although there were more cold snaps in January and February this winter.

Where growers struggled to control brown rust last season was often when the T0 was missed, and were then playing catch up the entire season.

There’s also risk from yellow rust, exacerbated by a larger percentage of later drilled crops this season – I’ve already heard reports of infections in Zyatt this spring.

It’s no surprise then that T0 is as useful as it ever was in the southwest, even though there is nothing as strong as we used to have in the armoury for Septoria control.

If you have active rust around GS30, use something with a strobilurin fungicide, such as fluoxastrobin with prothioconazole in Firefly®. If you’re more worried about yellow rust and are looking for fast knockdown prothioconazole plus tebuconazole is an alternative option.

Remember tebuconazole doesn’t mix with mesosulfuron-containing herbicides, if you’re doing both jobs at the same time.

Assess disease risk at T1

There are already reports of crops with high levels of Septoria in early drilled crops in the southwest as you would expect with plenty of rainfall but if it stays dry during spring it won’t spread as readily to new leaves, and if it is cool as well, it will slow down what cycling is happening.

Later drilled crops will have lower Septoria risk, but higher yellow rust risk, which is a scenario that lends itself to the use of Ascra® Xpro® using a dose of 1.0 to 1.2 L/ha. The further west you are in the southwest the higher the dose you’re likely to need to achieve better control of Septoria.

Ascra® Xpro® is very good on yellow rust for both preventative and curative control, as well as being a strong option against Septoria.

For crops with decent potential that you’re looking to invest in and push harder, we also have a new option in Plaxium®, in which the bixafen in Ascra® Xpro® is replaced with a stronger SDHI active substance isoflucypram. In trials last year it looked a good step up in disease protection and yield compared with Ascra® Xpro®.

Apply Plaxium® at 1.2 L/ha to give 50 g/ha of isoflucypram, which is the Bayer recommended rate. While many wheats in this region sound like they might not be worth a huge investment, this is good chemistry and worth a look.

Lastly, don’t forget the importance of correct timing for T1 sprays. It’s difficult to accurately hit leaf three on every tiller but aim for around 75% of leaf threes being fully emerged when you walk across the field.

Protect tillers to maximise yields in winter barley

As with winter wheat, growth has been slow so far in March in winter barley, which will probably push T1 sprays into early April.

This is the key timing for yield protection – it’s all about tiller retention. Any early disease can encourage the crop to abort tillers to protect resources, and once a tiller is lost, it cannot be compensated for in the remaining ears as it can be in wheat.

Ascra® Xpro® has been used by a considerable number of winter barley growers in recent years, delivering consistent and reliable disease control. It’s multiple modes of action are valuable, especially given the ongoing concerns regarding net blotch resistance to prothioconazole on the continent. Employing multiple modes of action is vital for prolonging the longevity of existing chemistry.

Applying SDHI chemistry at this timing will also unlock some physiological benefits, such as increased nitrate reductase activity for improved nutrient uptake and increased rooting, will also reduce stress on plants and limit tiller abortion.

For growers looking to manage costs even more tightly, Siltra® Xpro® could be considered, especially where lower levels of disease are present. It remains a proven option, delivering reliable disease control.

Ascra® Xpro® is also potentially an option later in the month at awns emerging, if you didn’t choose to use it at T1. It brings extra Ramularia activity compared with Siltra® Xpro®.

Spring break crop weed control

With planting already or set to get underway in potato, combining peas and spring field bean crops, weed control from pre-emergence herbicides is usually important with limited and sometimes expensive post-emergence options.

Emerger® is a valuable potential selection in all three crops, providing broad-spectrum control of grass and broadleaf weeds. It should be used as a component of a weed control programme rather than as a standalone product.

Application rates vary by crop – 1.75 L/ha in potatoes and 1.4 L/ha in the pulse crops. Emerger® has a long half-life, which can be helpful when you’re going to have bare ground for a reasonable amount of time following planting, helping to suppress weeds for several weeks.

In potatoes, we don’t recommend its use in crops planted under plastic, as we don’t have data to prove its crop safety, and remember that it must be applied at least seven days before potato emergence.

Oilseed rape flowering sprays

Flowering in oilseed rape always feels ages away in March and then is on you in a flash. Some growers will have been through with some prothioconazole in March to keep on top of light leaf spot, but the main timing for Sclerotinia control, plus topping up light leaf spot is around mid-flowering as the first petals begin to fall.

Aviator® Xpro®, with its combination of bixafen and prothioconazole, consistently demonstrates superior Sclerotinia control and significant yield uplifts of on average 0.3 t/ha in our trials, compared with prothioconazole. Bixafen’s physiological benefits also contribute to these observed yield increases.

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Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Aviator®Xpro® contains bixafen and prothioconazole. Emerger® contains aclonifen. Firefly® contains fluoxastrobin and prothioconazole. Plaxium® contains fluopyram, isoflucypram and prothioconazole. Siltra® Xpro® contains bixafen and prothioconazole.

Ascra®, Aviator®, Emerger®, Firefly®, Plaxium®, 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