You are here

Don't be complacent with your winter wheat T0

Agronomy Issues

T0 fungicide applications are typically applied 2–3 weeks earlier than T1 (leaf 3 emerged), as a way of reducing overwintered inoculum and providing a “buffer” in case T1 gets delayed due to inclement weather. It should be noted that in late drilled crops T1 may well be at a later calendar date, but as the crop rushes to catch up in the spring leaf 3 may emerge at an earlier growth stage. Timing should be optimised by dissecting the plant.  On well-established crops a T0 fungicide may well be economic this season as over-winter conditions have been conducive to mildew, yellow rust or brown rust development, particularly on susceptible varieties.

If growers have managed to establish a strong looking 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. Late drilled, backwards crops are more at risk of early infection of yellow rust and mildew which need to be addressed at first signs of disease.

Yellow Rust

Only four winter wheat varieties have seedling resistance to yellow rust. Do not to rely solely on adult plant resistance. Rust races can be extremely unpredictable and any active rust should be controlled with a fungicide application. Conditions over winter have been mild and moist. Yellow rust will continue to survive unless exposed to -5°C for multiple days. A T0 to control rusts will be particularly important in varieties which have poor adult resistance as it can be difficult to regain control once you are in a highly curative situation.

Yellow Rust

Only four winter wheat varieties have seedling resistance to yellow rust. Do not to rely solely on adult plant resistance. Rust races can be extremely unpredictable and any active rust should be controlled with a fungicide application. Conditions over winter have been mild and moist. Yellow rust will continue to survive unless exposed to -5°C for multiple days. A T0 to control rusts will be particularly important in varieties which have poor adult resistance as it can be difficult to regain control once you are in a highly curative situation.

Septoria tritici

It is rare that a T0 application for Septoria tritici at this timing delivers significant yield benefits, other than in high disease pressure situations. However, with continued unpredictable weather, it can insure against a delayed T1 in susceptible varieties. A large proportion of autumn cereal crops were drilled late this season and any measure to retain green leaf may prove beneficial. Expenditure need not be high and use of an appropriate multisite fungicide might be enough, for example Bravo or folpet.

Septoria tritici

It is rare that a T0 application for Septoria tritici at this timing delivers significant yield benefits, other than in high disease pressure situations. However, with continued unpredictable weather, it can insure against a delayed T1 in susceptible varieties. A large proportion of autumn cereal crops were drilled late this season and any measure to retain green leaf may prove beneficial. Expenditure need not be high and use of an appropriate multisite fungicide might be enough, for example Bravo or folpet.

Mildew

Mildew can now be found quite readily in some crops. This can be particularly damaging on backwards 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.

Mildew

Mildew can now be found quite readily in some crops. This can be particularly damaging on backwards 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.

To spray or not to spray?


All fungicide applications should be adapted to the scenario taking into account factors such as variety and disease pressure. For best results, use a 3D defy nozzle at 100L/Ha to get good coverage of the crop. Consider the potential yield and quality consequences if a T0 spray is omitted – remaining in a protectant scenario is the most economical option.

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. Second wheats on poorly consolidated seed beds are at greatest risk of take-all infection. Many trials have shown that a T0 application of Amistar can be beneficial in enhancing performance in take-all scenarios. 

Checking stem bases and roots for symptoms of these diseases in the spring is an excellent indicator of risk.

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. Second wheats on poorly consolidated seed beds are at greatest risk of take-all infection. Many trials have shown that a T0 application of Amistar can be beneficial in enhancing performance in take-all scenarios. 

Checking stem bases and roots for symptoms of these diseases in the spring is an excellent indicator of risk.

30.03.2020