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Get early season disease management right to set the foundation for yield

Winter Wheat
18.03.2022

As the days are getting longer, it is beginning to feel like spring and wheat crops are beginning to move. A T0 fungicide may well be economic this season as over-winter conditions have been conducive to disease development, with mildew, yellow rust and Septoria now visible on susceptible varieties.

There is a wide range of wheat development across the country as a result of the relatively open drilling season in the autumn which meant plenty of early and later drilled crops. If growers have managed to establish a strong looking, high potential crop they should ‘go-for-gold’. Adopting a robust and well-timed fungicide approach to maximise yield potential will be key. Equally, it is widely recognised that disease pressure is typically lower in later drilled crops, so growers should remain vigilant and adapt their applications to the situation. Later drilled, backward crops are more at risk of early infection of yellow rust and mildew which need to be addressed at first signs of disease.

T0 fungicide applications are typically applied 2–3 weeks ahead of the T1 (leaf 3 emerged), as a way of reducing overwintered inoculum and providing a “buffer” in case T1 gets delayed due to inclement weather. Timing should be optimised by dissecting the plant to ensure you are targeting the right leaf. 

Yellow Rust

Although the number of varieties with seedling resistance has increased on the newest Recommended List, the majority of wheat in the ground this season is seedling susceptible, including the Syngenta varieties GLEAM, GRAHAM and SY INSITOR. The UK yellow rust population is both extremely dynamic and complex and as we have seen with several varieties in the past, there is no guarantee of future performance with regard to yellow rust resistance. Yellow rust populations can rapidly overcome adult plant resistance and it is therefore important to monitor all crops closely, regardless of their adult plant resistance rating, particularly following mild winters where rust levels may be starting to build up as we enter spring. 

A T0 to control rusts will be particularly important in varieties which have poor to moderate adult resistance as it can be difficult to regain control once you are in a highly curative situation. AMISTAR has excellent protectant control of yellow rust and is a good option on susceptible varieties, however, if yellow rust is already present, a rust active triazole with curative activity will be preferred.

If you observe active yellow rust at this point in the season, you should be prepared to treat it early to stay on top of it – particularly if growing varieties susceptible to yellow rust. A rust active T0 is often economic where there is high risk.

- Seeds Technical Expert, Matthew Bull

In order to help monitor the spread of rusts across the UK, Syngenta have launched a new web-based service to help UK wheat growers and agronomists stay a step ahead of unpredictable yellow rust outbreaks.

The web app can be accessed here.

Mildew

Mildew can now be found quite readily in many crops across the country at this time. This can be particularly damaging on backward crops as low levels of infection can cover a significant proportion of green leaf. For preventative mildew control consider Unix or prothioconazole, and if infection has already occurred use a specific mildewicide with curative activity.

Eyespot & Take-all

A T0 application can also be beneficial for the control of eyespot. Generally, eyespot and take-all risk are lower in later drilled crops, however wet and mild conditions over winter have meant that overwintered inoculum levels have built up and there may be a significant risk.

GLEAM and SY INSITOR are widely recognised as strong second wheat choices, however, no variety has resistance to take-all and foliar fungicides may help manage risks. Early drilled second wheats on poorly consolidated seedbeds are at greatest risk of take-all infection and should be monitored. Trials and experience have shown that a T0 application of AMISTAR can be beneficial in take-all scenarios. AMISTAR also has the added benefit of rust control which makes it an excellent choice early in the programme.

Septoria tritici

It is rare that a T0 application for Septoria tritici delivers significant yield benefits, especially on varieties with good resistance such as GRAHAM. However, with continued unpredictable weather, it can ensure against a delayed T1 which may be particularly valuable in more susceptible varieties. Expenditure need not be high and use of an appropriate multi-site fungicide might be enough, for example folpet.