While the T1 and T2 timings have been the natural home of SDHI fungicides, after this most unusual of seasons, there is a case for them at T3.

The big unknown says AICC’s Patrick Stephenson is the weather. In a normal season that wouldn’t be such a problem, but many T1 and T2 went on early with T0 sprays omitted, or also early to tackle yellow rust, he argued.

“An SDHI is going to give a boost to septoria and rust control over straight azole. If only one SDHI has been used in the programme, it is an option if late foliar disease is fuelled by warm and wet weather.”

He pointed to 2012 where the inclusion of an SDHI delivered value. That turned out to be one of the wettest years on record, but early on it was particularly dry and some areas bound by hosepipe restrictions. Ahead of GS32 (T1) septoria pressure was extremely light, but disease pressure increased rapidly when prolonged wet weather arrived.

Other factors come into consideration this year, suggested Mr Stephenson. With crops looking promising and respectable grain prices, a small yield increase is all that’s required to pay for the premium over straight azole.

He also pointed to quality issues: “If you’re growing a variety like Skyfall then grain quality is a criteria. Shriveled grain or dull samples may not impair yield greatly but can hit quality. Including an SDHI also fits the fusarium threat, as many have a prothioconazole base,” he pointed out.

Bayer’s James Wilkins said he agreed that an SDHI was a viable T3 option this season as many went with azole in combination with strob and/or multisite mixtures at GS32. “If you look at our Rapid Disease Detection results for April, we had just a handful of results over 1.000 ng/ul, and these were mainly limited to early drilled, susceptible varieties. The potency of an SDHI wasn’t needed in many T1 situations,” he said.

He noted that trials highlighted that for every day green leaf area was maintained in the upper canopy post GS39, it could be worth as much as 0.45t/ha in some seasons.

“Where an SDHI wasn’t used at T1 it could be worthwhile. Aviator (prothioconazole + bixafen) delivered a sufficient dose of prothioconazole to manage fusarium, plus you’re getting enhanced foliar control and greening benefits from bixafen,” he concluded.