Precision is increasingly important when it comes to spray timings for septoria control.
Greater attention to spray timings keeping in mind the limitations of fungicide groups in terms of curative action will help growers get the most from chemistry as well as managing development of resistant septoria strains.
Adama technical specialist Andy Bailey says when it comes to spraying, precision is important. “People often blame resistance when sprays are not working but when you ask about application timing and spray intervals, they are applying as they always have done, assuming they can get themselves out of a hole, but this is not the situation anymore.”
While septoria resistance to SDHIs has so far not been confirmed in the field and is mainly associated with trial sites where, for example, SDHIs are used without azoles or multi-sites, guarding against it is important, says Mr Bailey.
“Resistance to SDHIs is currently evident as insensitive septoria strains within populations rather than reduced product performance in the field. Warning signs are clear from monitoring data but we are not there yet and performance of SHDI products in the field remains robust.
“Because of what [AIs] we are losing and also likely restrictions on existing fungicides such as chlorothalonil going forward, control is very much about doing things in a precise manner – targeting to apply appropriate products at the proper timing and keeping ahead of the disease.”
Integrated control is also vital going forward, he adds.
“Fungicides are just one part of it. Now there are some much better resistant varieties available. Delaying drilling can be difficult but it does have quite an impact on how much septoria builds up over winter. Disease forecasting is also likely to have a role going forward.”
For growers choosing varieties with low resistance to septoria, getting ahead of the disease is particularly important, says Mr Bailey.
“I would want to be ahead of the disease and not get into a curative situation.
“Adama’s multi-site, folpet, keeps you in a preventative situation so you don’t get into a curative situation and for this the use of multisites is valued and well established.”
While there is much debate over spray timings, Mr Bailey advocates a ‘leaf layering’ approach. If crops are not sprayed at T0, which protects leaf 4, the T1 timing must be spot on, he says.
“Applying a T0 provides insurance against septoria if the T1 is delayed due to poor weather conditions.”
If the interval between the T1 and T2 timings extends to more than three weeks, there is a strong argument for a T1.5 timing, says Mr Bailey.
“This season crops were quite advanced, with the T1 timing early, then things slowed down. With some crops there was a gap of four weeks plus between T1 and T2 – the perfect scenario for a T1.5.
“T1.5 should be timed when leaf 2 comes out. It doesn’t need to be a huge, powerful spray but based around a multisite to protect that leaf until you can go in with T2 maybe seven to 10 days later. It gives protection and peace of mind. It may in future become a little more routine than at the moment.
“Leaf 2 is the one leaf we don’t spray as soon as it comes out; historically this has been because azoles were so curative – even if there was some infection in leaf 2 a triazole would have cleared it up but its curative activity has eroded now.”
With the choice of fungicide solutions available to growers coming under increasing pressure, both in terms of effectiveness due to increasing resistance and availability as a result of regulatory pressures, growers and agronomists need to ensure each new leaf is adequately protected from infection, thereby avoiding the need to apply curative treatments.
Adama’s concept of ‘Precision Crop Protection’ advises growers to use good quality, well proven formulations of appropriate active ingredients at the most appropriate time and at the correct dose to provide effective protection.
In terms of providing protection against septoria infection, the concept requires each new leaf to be protected during the first half of the disease’s latent period of infection from when the fungus penetrates the leaf to disease symptoms manifesting themselves. However, the three or more weeks between T1 and T2 applications can render any new leaves which appear during this period susceptible to infection.
Growers should therefore consider the concept of ‘leaf layering’ to ensure optimum protection during the ‘at risk’ period. Applying a T1.5 treatment – first choice should be a multi-site product to provide contact protection against septoria, potentially mixed with a strobilurin to protect against the threat of rust, or an azole/morpline if active rust is present – will ensure each new leaf is properly protected from infection, thus negating the need to rely on curative solutions.