Set strong foundations with a timely T0 – South East Farmer

Rust management is a numbers game. You must act early to slow it down before inoculum builds, and in most situations that starts with the growth stage 30 (T0) fungicide.

Eastern counties typically face the highest yellow rust risk, and last year we saw particularly early appearance of brown rust in many wheat crops across southern England. Very few varieties have seedling stage resistance to brown rust, so if it does come in early, risk must be managed promptly. Yield loss to brown rust infections can be very high, and susceptible varieties must be managed accordingly.

Whether last year’s high rust pressure means more inoculum this spring remains to be seen, as it may be countered in part by January’s cold weather. Several hard frosts (at least -5°C or below) can delay rust onset, while milder conditions could result in earlier pressure again.

Traditionally, yellow rust favours cooler conditions, but there are signs it is adapting to warmer weather, while the opposite appears true of brown rust, which seems better at coping with cooler temperatures.

A good T0 is therefore a sensible option, as it sets the foundations for effective disease control and, crucially, helps manage the pressure on subsequent GS 32 (T1) treatments and key yield-building leaves.

With a wide range of drilling dates and crop development across the region, priority should be given to earlier-sown, forward wheats.

Strobilurins or azoles (notably tebuconazole) are the main options for curative rust control at T0, and those looking to boost Septoria protection should consider including a multi- site like folpet. It is best to avoid mainline azoles that will feature later in the programme, such as prothioconazole.

Remember, though, late-sown and stressed crops can be susceptible to yellow rust as plants are less well developed and natural defence mechanisms are reduced, even in varieties with higher varietal ratings. This was evident last year, so is worth recognising if crops have sat in wet, waterlogged soils for prolonged periods this winter.

Although rust has become the focus for T0 fungicides, it is important not to overlook the importance of this timing for manipulating crop physiology too.

As tillering stops and crops enter stem extension, we can use plant growth regulators to manage apical dominance and help balance the flow of nutrients and energy into leaves, tillers and the grain sites beginning to develop. The aim is to give plants the best chance of supporting as many productive tillers as they can.

There is an important distinction between this early growth ‘manipulation’ and the use of PGRS at the later GS 31/32 or 37/39 timings, where the focus is on growth ‘regulation’ by shortening and strengthening the stem to reduce lodging risks.

Phosphite-based biostimulants are also worth considering at T0, as experience shows they can help stimulate and maintain tillers and promote root growth, with all the knock-on benefits that brings in terms of nutrient/water uptake and crop health.

Finally, although there is a wide range of drilling dates and crop development coming out of winter, crops are very good at catching up as rising temperatures and day length drive growth. This can make spray timings tricky, so monitor crops closely and ensure you identify growth stages correctly. Good coverage is vital, too, so while there is an understandable desire to get the job done quickly when workloads are busy, crops are growing rapidly and weather is catchy, this must not be at the expense of product efficacy.