Spraying on flowering oilseed rape© Tim Scrivener

Oliseed rape growers have a new SDHI fungicide option this season, boasting potential yield increases of 0.45t/ha.

Specifically designed for application at the flowering stage, Symetra (azoxystrobin + isopyrazam) uses two actives to guard against sclerotinia and other late diseases.

See also: New OSR flowering spray boosts yields by 0.23t/ha

Sclerotinia, otherwise known as stem rot or white mould, is most common during flowering and can have a significant impact on crop yield and can lead to epidemics if not controlled.

A combination of actives work to block disease infection and give extra green leaf protection, says Syngenta oilseed rape technical manager James Evans.

“Isopyrazam binds strongly on to the leaf and stem wax and quickly accumulates into a protective layer.”

He points to extensive trials across Europe which found an average 66% drop in sclerotinia infection of stems with 0.45t/ha increase in yield.

The new fungicide also saw late-season alternaria effects limited to just 4% of pods compared with 27% infection in untreated crops.

Mr Evans recommends an initial treatment at the first sign of petal fall for maximum effectiveness.

“Application trials have demonstrated the best efficacy with Symetra treatments timed to coincide with the first petal fall, typically when the crop is at 50% flowering.

“Additionally, when used as part of a two-spray programme with azoxystrobin at early flowering, it provides extended disease coverage which, coupled with the added physiological benefits of green leaf retention, allows the potential of crops to be really pushed.”