Arable News

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Resistance management needs balance with yield protection

Don’t farm this season’s crop on last season’s hindsight is a key message when considering the 2016 wheat fungicide campaign

Don’t farm this season’s crop on last season’s hindsight is a key message when considering the 2016 wheat fungicide campaign. Dominic Kilburn writes.
The recent concerns following septoria resistance to SDHI fungicides being found serves as yet another reminder to growers and agronomists this season to be extra vigilant in terms of using key fungicides in mixtures during the forthcoming spring fungicide campaign.
That’s according to BASF business development manager Ben Freer (left) who says that although there were very low levels of the resistant strain found it does make you consider just what it would be like to grow a crop of wheat without triazole and SDHI fungicides to hold back predicted high levels of disease. “And that’s what we all need to think about this spring when we apply fungicides – just how very difficult it would be without them,” he warns.
Mr Freer suggests that the pressure will come if growers say they can’t afford a full fungicide programme and they make the decision to cut back on spend. However the best way to make money is to aim for a high yielding crop, he points out. “Growers have made the decision to plant a crop and so why wouldn’t they manage it for maximum yield?
“It’s no good people saying they spent too much on fungicides last season and therefore it makes sense to spend less this year. If they do that then they’re likely to get it wrong,” he stresses. “You can’t farm this season’s crop based on the hindsight from last year; no season is the same.”
He admits that, when it comes to protecting SDHI fungicides from resistance, there can be an understandable dilemma in the best way to use them. “In the short term there is a need for resistance management and being wary of over use of individual active ingredients, but then we must be pragmatic and protect yield if the disease is there.”

T0 thoughts
Disease pressure for this season is high, he reminds growers – with septoria, yellow rust and brown rust all currently visible in crops – and, with the mild winter continuing, disease is likely to get off to an early start, spreading to the important leaves. “Last year there was no pressure early on in the season and eventually it came in late, while this year there is the potential for it to be the other way around,” he observes.
The T0 spray application doesn’t always give you a large yield boost but it does give you peace of mind, continues Mr Freer, who describes it as a management tool to wipe the slate clean at the start of the spring and get the crop off to a good start.
“The only danger of a T0 is that there is the temptation to get on with it too early, particularly in a season like this, and then lose the point of putting it on in the first place if the gap until T1 gets too large and the whole programme ends up being brought forward or getting stretched.
“If disease does get in between the timings it then becomes very difficult to catch up with it and an ‘in-between’ spray timing may be needed,” he warns.
In addition, with the recent news of a new race of yellow rust being discovered in the UK for the first time, it underlines the need when regularly checking for disease in all varieties, to ensure that an apparently resistant variety hasn’t fallen foul of the latest mutation, he says.
In order to protect crops from the start, a septoria- and rust-active triazole plus chlorothalonil is required at T0 to suffocate and stifle disease, and growers should aim to use chlorothalonil especially at the early timings, points out Mr Freer.
“Chlorothalonil provides a different mode of action to the triazoles and SDHIs,” he says. “It offers protection against septoria (but not the rusts) and acts as a very good barrier at the beginning of the season,” he adds.
An alternative option is to use Comet 200 (pyraclostrobin) with chlorothalonil at T0 – this will give good control of rust and protect leaf 4 from septoria, he suggests.
Thereafter, Mr Freer suggests that cleaner crops could have an application of Tracker (boscalid + epoxiconazole) + chlorothalonil at T1, rather than one of the second generation (newer) SDHIs but, if significant disease pressure is present, a T1 should contain 1.0-litre/ha of SDHI Adexar (epoxiconazole + fluxapyroxad) + chlorothalonil.
“The top three leaves of the plant will be the ones that give you yield and the greener they remain during the season the better,” he concludes.

  • Written by: Farmers Guide
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