Growers in many parts of the country  are facing an even higher risk from rust infections this season than they did in the disastrous year of 2007, making a robust triazole-based March T0 vital for many if the threat of brown rust, in particular, is to be effectively countered.

This is the timely warning from research-led agronomy leader, Agrii based on extensive winter disease monitoring by Masstock and UAP researchers and agronomists.

“We recorded very high levels of late-season brown rust infestations in many wheat crops last season, reported R&D manager, Colin Lloyd at a special February briefing.  “The disease came in too late to affect official variety disease scores.  In most cases it had little or no impact on performance, although we recorded trial yield reductions of up to 2.5 t/ha in some varieties.    It has, however, meant massive amounts of inoculum carryover to the current crop.

“At the same time, planting records show that around 70% of our national wheat area is currently in varieties with a brown rust resistance rating of 5 or less – even before any account is taken of the new race of the disease that became apparent (alongside a major new yellow rust race) in 2011.

“Early sowing and one of the warmest autumns on record meant dense crops of lush wheat going into an early winter as least as mild as 2006/7 too.  So it’s not surprising we’ve seen the most significant build-up of wheat disease for many years across such a large area.

“At one of our local sites, for instance, 10 of the 21 varieties in our early drilled trials went into the winter with brown rust levels of more than 20%,” he noted. “And we’ve continued to find well-established yellow and brown rust infections in the base of crops throughout the winter. The early February freeze will have done some good.  Even so, we ignore the levels of early infection we’ve seen this season at our peril.”

While septoria will remain the Number One early season threat to most wheat crops, Colin Lloyd and his Agrii colleagues stress that growers will need to be especially alert to the threat from both brown and yellow rusts this spring, pointing out that trying to play catch-up with these diseases, like so many growers were forced to do in 2007, is something to be avoided at all costs.

This will make a well-planned  and managed T0 more important  than ever for many crops,  both in terms of its specification and its execution.

Agrii research and development project manager, James Southgate explains that Masstock and UAP trials over a  number of years have shown a triazole with good activity against rust as well as chlorothalonil at T0 delivering yield benefits of 0.5 t/ha even in seasons with low early disease pressure.  And this is in addition to the yield advantages secured from either earlier fluquinconazole seed treatment or subsequent SDHI chemistry at T1 or T2.

“Fluquinconazole seed treatment has proved immensely valuable in keeping on top of early rust infections,” he insisted.  “But even with it we’ve seen yellow and brown rusts come into our plots before normal T1 timing in mid-April.  So it’s certainly no replacement for a T0. Nor, we’ve found, is even the best SDHI at a later timing.

“The key – especially where initial crop disease levels are high and varieties aren’t as resistant as they could be – has to be to nip infections in the bud early enough with a T0 in mid-March. This means you won’t be tempted to drag your T1 forward to tackle early problems,  leaving too much of a gap for the disease to cycle ahead of your T2.

“As well as using a robust triazole-based T0, prioritising varieties with less-than-ideal levels of rust resistance and those which didn’t receive a foliar disease active seed dressing, the current disease threat makes first class spraying practice to maximise crop penetration essential,” he adds. “Despite the workloads and pressures, more than anything else this means not travelling too fast.”