Crops are set up to benefit from three-pronged fungicide mix at flag leaf

BE sure to monitor crop growth closely over the coming weeks in order to achieve correct spray timings for forthcoming flag leaf (T2) fungicides, wheat growers are being urged.

The sudden shift to hot, damp weather in early May, combined with varying drilling dates, has produced wide variations in crop growth, says Syngenta cereal disease specialist Matt Pickard.

Backward crops are now surging ahead and with the flag leaf contributing more than 40% yield, just one day's delay in T2 fungicide application is capable of losing 0.07 t/ha in yield. It will be vital to inspect fields regularly, he says, to ensure crucial spray timings aren't missed.

"Crops look good this season, but there's a real danger that if they're left too long between inspections, spray timings could slip. Also, due to T1 fungicides being applied a week later than normal this season, growers may be tempted to make similar delays at T2.

"Any delays will leave crops wide open to yield losses, therefore T2 fungicides need applying as soon as possible once the flag leaf is fully emerged."

In particular, Mr Pickard says Septoria and rusts will be the key diseases to protect against this season. But by treating flag leaves promptly while still clean, growers will be able to take maximum advantage of the protective and greening benefits of a strobilurin.

"We've already picked up reports of yellow rust. Now with the warmer weather here this will shorten the time required for infection cycles of Septoria tritici.

"If growers can get on early enough they should be in prime position to benefit from protective fungicides this season. A strobilurin + Bravo mix such as Amistar Opti will be ideal. It's not only got the Amistar ingredient (Azoxystrobin) for maintaining green leaf area and controlling yellow and brown rust, but also the Bravo ingredient (chlorothalonil) for protecting against Septoria tritici.

"Amistar is a highly systemic strobilurin, moving to protect new growth in the plant, which has the added benefit of allowing lower water volumes to be used. Mixed with a triazole fungicide it offers a very cost-effective three-pronged flag leaf mix."

Last year in trials, Mr Pickard says an Amistar Opti + triazole mix gave an extra 0.7 t/ha over straight triazole and 0.4 t/ha over a triazole + Bravo mixture. "I know there has been some debate about whether to include a strobilurin fungicide, but growers can't afford to turn their back on this sort of yield increase at current grain prices.

"Of all the leaves, the flag leaf is the most important one to protect. So T2 is undoubtedly the best time for using a strobilurin. It's just a case of choosing the right one and monitoring crops to get that all-important timing correct."