Disease control and other agronomy advice for East Anglian growers in May

1) Finish T1 sprays in later drilled wheat crops

Earlier drilled crops should have received T1s by the time you read this, but some later drilled ones will probably need spraying as a priority. Timing is key with the target final leaf three fully emerged.

If rain has come, disease pressure might have increased from Septoria and rusts, although drilling date will temper Septoria risk to some extent. In a lot of cases Ascra® Xpro® should make a cost-effective option for these crops but if there are higher levels of disease, especially yellow rust, consider using Vimoy® plus a partner such as Proline®. Prothioconazole will also help with mildew control.

2) Weather will determine disease risk at T2

Writing this at least a month ahead of T2 sprays makes it impossible to know what disease pressure you will be facing when applying flag leaf sprays. As ever, weather will be a big determining factor.

If it stays relatively dry through the next month and disease pressure is low, that opens the opportunity to use the less expensive chemistry, such as Ascra® Xpro®, especially on lighter land crops where moisture levels determine yield potential to some extent.

If the weather has turned wetter, which is what is currently forecast, then a more robust programme will be required with Septoria and yellow rust risk increasing.

In this case, care is needed for product choice as there could be restrictions depending on what was applied at T1. For example, isoflucypram, fenpicoxamid and pydiflumetofen all can only be applied once a season.

A very strong option for high pressure Septoria and rusts would be Jessico® One plus Vimoy® assuming neither fenpicoxamid nor isoflucypram were used at T1. Miravis® Plus is also a very strong option for Septoria but doesn’t have quite the level of activity against rusts that Vimoy® brings with Jessico® One.

Perhaps where Septoria pressure is slightly lower, but rusts are a concern, Plaxium® is another option. A co-formulation of fluopyram, isoflucypram and prothioconazole, it provides excellent all-round activity where the addition of isoflucypram is worth the additional cost over Ascra® Xpro®.

3) Protecting winter barley crops

Stressed crops, as well as ones with disease, will need protecting with an awns emerging spray in winter barley. Disease pressure is currently low, but again that might have changed if rain has arrived in the latter half of April.

But if it has stayed predominantly dry, winter barley crops are likely to be quite stressed, even if they are lower risk for disease infections, which can be a risk factor for Ramularia.

Where it wasn’t used at T1, Ascra® Xpro® provides a good option at this timing. It helps crops that are drought stressed with its physiological benefits and also protects against brackling, which might be more a problem if straw dries out.

Alternatively, Siltra® Xpro® could be used – the dual modes of action in both products are helpful in controlling disease.

If the weather has changed and disease pressure has ramped up, then Miravis® Plus is another option – if your costs allow it.

4) One or two sprays for spring barley disease control?

While spring barley drilling conditions were good, crops would also benefit from some rain. Growth has been slow but as soon as rain arrives, which hopefully it has by the time you read this, they’ll start pushing ahead.

With good yield potential, I’m in favour of a two-spray fungicide approach, which will help protect tillers to maximise yields. Equally I can understand the hesitation with current barley prices and if disease pressure is low. But the risk is always there if the rain arrives and there is a disease outbreak.

Ascra® Xpro® and Siltra® Xpro® are good options for either strategy. Ascra® Xpro® is stronger on Ramularia, while both can also be bolstered by folpet, if needed, to create a stronger all-round treatment.

5) Remember temperatures affect the oil rates in sugar beet

Any rain in April will likely have created weed flushes, which might still need treating with second and / or third herbicide applications in May.

Betanal® Tandem® brings broad spectrum weed control as a base, in mix with a residual partner. The addition of an adjuvant oil will also help with efficacy, but remember the dose is dependent on the maximum forecast temperature on the day of application. Don’t add it if temperatures are going to be above 21C.

6) New insecticide to help control aphids

Aphids that can transmit virus yellows in sugar beet are forecast to arrive in crops from around 12 May, although warmer weather could bring that date forward. Crops will need careful monitoring from the beginning of May to see whether the threshold of one aphid per four plants up to 12 true leaves is exceeded for using insecticides.

A useful addition to the armoury for this season is Sivanto® Prime which will control aphids that transmit virus yellows. It’s best used at an early timing in the programme due to its contact and translaminar activity, which means it can control aphids hiding on the underside of leaves.

The latest timing of application is 9 true leaves of the crop, which is another reason for using it early in the programme.

Sivanto® Prime can also be used in potatoes, peas, beans and carrots to control aphids and other sucking pests.

7) Plan blight programmes carefully

After the confirmation of two instances in the UK of the new EU_46 strain of potato blight, which has been found to be resistant to OSBPI fungicides, such as Zorvec®, in Europe, planning blight programmes will be crucial.

While those were isolated cases, it is something growers will need to be vigilant on because we now have two strains in Europe that are resistant to either or both CAA fungicides and the aforementional OSBPIs. Typically, these two modes of action are used in around 50% of applications.

Neither active in Infinito®, propamocarb and fluopicolide are in the CAA or OSBPI mode of action groups, so are not impacted by these resistant strains. With the Fungicide Resistance Action Committee (FRAC) advising to not begin programmes with either a CAA or OSBPI product, limiting numbers of applications of these modes of action, as well as advising alternating and mixing of modes of action, Infinito® fits well at all stages of the programme.

Historically, Infinito® has been saved for the latter part of the programme to take advantage of its tuber blight activity – that remains a good place to use it, but it’s worth also slotting in applications earlier in the season.

8) Look after good looking oilseed rape crops

Maybe the bar of expectation for oilseed rape is now extremely low but growers generally seem pretty happy with oilseed rape crops this season, where they survived pigeon damage.

Flowering started quite early, and depending on conditions, it could be quite a prolonged period this year. Initial flowering fungicide sprays will provide about three weeks protection from Sclerotinia so if flowering is prolonged past that period, a second spray might be required, especially if there is rain.

Aviator® Xpro® is a potential option with the SDHI in bixafen providing some additional greening benefits. Alternatively, an azole or boscalid could be options.

-----

Aviator® Xpro® contains bixafen and prothioconazole. Ascra® Xpro® contains bixafen, fluopyram and prothioconazole. Betanal® Tandem® contains ethofumesate and phenmedipham. Infinito® contains fluopicolide and propamocarb. Jessico® One contains fenpicoxamid. Miravis® Plus contains pydiflumetofen. Plaxium® contains isoflucypram, fluopyram and prothioconazole. Proline® contains prothioconazole. Siltra® Xpro® contains bixafen and prothioconazole. Sivanto® Prime contains flupyradifurone. Vimoy® contains isoflucypram. Zorvec® contains oxathiapiprolin.

Aviator®, Ascra®, Betanal®, Infinito®, Jessico®, Plaxium®, Proline®, Siltra®, Sivanto®, Tandem®, Vimoy® 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