With the choice, scope and efficacy of curative fungicides coming under increasing pressure – both in terms of their effectiveness due to potential resistance, and their availability due to regulatory pressures – wheat growers should consider the application of a T1.5 treatment to ensure Leaf 2 is adequately protected from septoria.
That is the advice from Andy Bailey, fungicide technical specialist for Adama, who advises growers that the most effective way to control septoria is to prevent infection from occurring in the first place.
“This means ensuring each newly emerged leaf is protected prior to the first infection period – in essence, before the first spores land on the leaf and germinate,” Andy explains.
“Whilst Leaf 3 and the flag leaf (Leaf 1) are routinely protected with well-timed applications at T1 and T2 respectively, Leaf 2 often goes unprotected at its emergence, with growers relying on the subsequent T2 application to give kickback curative activity against any existing latent infection. This puts Leaf 2 at significant risk to the infection progressing beyond chemical control, especially if the T2 application is delayed.”
Growers should therefore consider the concept of ‘Leaf Layering’ (applying protection to each new leaf as it emerges) to ensure optimum protection of ‘at risk’ crops such as those which were drilled early, drilled using a septoria susceptible variety or located in areas prone to septoria infection. For Leaf 2, this means applying a T1.5 treatment at GS33 to treat the fully emerged leaf.
“The first choice of active ingredient for any T1.5 treatment where septoria is the driver should be a multi-site such as folpet,” Andy continues. “Folpet will provide good levels of contact protection against septoria, and can be mixed with a strobilurin to protect against the threat of rust, or an azole/morpholine if active rust is present.”
In addition to providing good control of septoria and offering activity against rust, folpet also takes the pressure of resistance off azoles and SDHIs: “Like other multi-site fungicides, folpet affects several different metabolic sites within a pathogen,” Andy continues. “This gives it a very low risk of resistance, with modelling work predicting that the addition of folpet to the tank-mix could theoretically extend the fully effective lifetime of medium to high risk fungicides. For example, the fully effective lifetime of epoxiconazole could have been extended from 8 to 16 years, with the lifetime of pyraclostrobin going from 4 to 8 years.”
Field trials and septoria strain analyses conducted in 2014 also showed the addition of folpet to an azole stopped the selection of resistant septoria strains, preventing any further slippage in fungicide performance. Similar results were also seen in 2015 trials carried out on SDHIs. Folpet has also been proven not to interfere with the curative kickback activity of partner azoles or SDHIs.
“Applying a multi-site at T1.5 will ensure the newly emerged Leaf 2 is protected from septoria infection, thereby moving away from the reliance on the curative activity from T2 applications to control any latent infection and the risks associated with allowing the disease to get away. With the current arsenal of fungicides having a reduced curative capacity this will not only ensure the crop remains cleaner for longer, but will also take the pressure off subsequent application timings,” Andy concludes.
Folpet is available as Arizona (500g/l folpet SC) as a flexible mixing partner, and Manitoba where it is co-formulated with a leading azole (50g/l epoxiconazole + 375g/l folpet SC). In both cases, Arizona and Manitoba are based on tried, tested and proven formulations with both offering broad spectrum flexible disease control for cereal crops.
