Growers are advised to maintain their guard against cereal diseases in well-established winter crops this spring.
Most winter wheat has established well and looks promising after early autumn drilling. But septoria risk could be higher in larger biomass crops. So too could yellow rust – especially in varieties affected by the YR15 resistance gene breakdown.
Risk management
“Traditionally, early drilling is seen to favour Septoria, while later drilling favours rust,” says David Howard, agronomy innovation director at Hutchinsons. “Later-sown crops are less mature, so their resistance is less capable when rust comes in.”
Rust risk could also be greater in early-sown wheats if a variety’s resistance is compromised, adds Mr Howard. Those crops are likely to have more biomass and will have been in the ground longer to capture spores, he explains.
“Prolonged cold is likely to have slowed and delayed rust arrival in crops, but to what extent is always challenging to predict until we get to spring, and it is unlikely to have gone completely.”
Growers should avoid being lulled into a false sense of security by relatively low disease incidence last season, when a cold January and February – followed by a dry spring and summer – helped keep a lid on problems.
“The situation could be very different with more normal weather patterns this season. Higher soil nitrogen may further increase disease risk, especially where large first doses are applied.”
Protect potential
Agronomist Katie Davies says that overall, crop potential across central England and elsewhere is the “best we have seen for several years” following excellent establishment during autumn and early winter.
“It is quite wet out there now, but we’ve had a really good foundation period, which is essential for achieving high yields.”
Given the current pressure on farm finances, Ms Davies acknowledges there will be growers that are looking to save money on inputs, but warns that this should not necessarily be at the expense of yield.
“It is a very tricky balancing act. We need to be really honest with the potential of the crop and maximising this potential with justified inputs.
“Crops look good, but they are certainly going to need protecting because disease and lodging pressure is likely to be high. A robust programme will be essential in many cases to realise this potential.
“Growers need to be careful they don’t cut too much spend out of the programme, however tempting it is to do so. Ultimately, on-farm decisions will depend on an individual’s appetite to risk.”
Choose wisely
Early fungicides at pre-T0 or T0 should generally focus on yellow rust control, with Septoria pressure remaining the biggest determinant of mainline T1 and T2 fungicides. But folpet should be considered too where Septoria pressure is particularly high by T0.
“Don’t overlook mildew pressure either,” says Mr Howard. “Use chemistry wisely to its best effect, considering the strengths of individual actives, and where they are best used in the programme.
Label restrictions prevent the use of some products before Growth Stage 30 – so biological controls may be an option to keep disease at manageable levels when fungicide options are limited, although they are a protectant and not curative.
Azoles, such as tebuconazole, prothioconazole and metconazole, generally offer good curative rust activity and are relatively cost-effective, although longevity may not be as good as strobilurins
“Strobilurins have good activity and longevity for rust control, but only on leaves present at the time of application. This longevity benefit reduces where new leaves emerge after treatment, so strobs may be better at T1/T2 to protect key yield-building leaves.”
Looking ahead
Another implication of early drilling is to extend the phyllochron – the gap between leaf emergence, says Mr Howard. This challenges traditional T-fungicide timings, which are designed around Septoria management and its 360 day-degrees latent period.
“Yellow rust in contrast, operates on a much shorter timeline, nearer 180 day-degrees, so there may be a need for interim sprays, such as a T1.5, in higher-risk crops.”
Increasing inputs at a time when gross margins are already strained is unpalatable, acknowledges Mr Howard. But maintaining yield potential will be essential if disease pressure builds, he adds.
“Assess individual fields and varieties for risk and look for efficiencies across all inputs, rather than arbitrarily reducing the fungicide budget, given they offer one of the most consistent returns on investment.”