Unusual spring weather means growers should consider using an SDHI fungicide in the T3 timing slot to control late foliar disease in wheat, say agronomists.
The T1 and T2 timings are the natural home of SDHI fungicides. But Patrick Stephenson of the Association of Independent Crop Consultants says there is a case for them at T3 following another challenging spring.
The big unknown is the weather, says Mr Stephenson. In a normal season, that wouldn’t be such a problem. But many T1 and T2 sprays went on early this year with T0 sprays omitted or also applied early to tackle yellow rust.
“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.”
In early 2012, for example, it was so dry that hosepipe restrictions imposed in some areas. Septoria pressure was extremely light ahead of GS32 (T1) but disease pressure increased rapidly when prolonged wet weather arrived.
Other factors also come into consideration suggests Mr Stephenson.
With crops looking promising and respectable grain prices, a small yield increase is only required to pay for the premium over straight azole.
“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.”
This is when including an SDHI also fits the fusarium threat, as many have a prothioconazole base, adds Mr Stephenson.
Trials have highlighted that an SDHI can be worth as much as 0.45t/ha for every day green leaf area is maintained in the upper canopy post GS39 in some seasons, according to James Wilkins of Bayer.
Mr Wilkins says: “Aviator (prothioconazole + bixafen) delivers a sufficient dose of prothioconazole to manage fusarium – plus you’re getting enhanced foliar control and greening benefits from bixafen.”