CSFB damage could leave OSR more vulnerable to sclerotinia

Preventative

Applications, though, have to be preventative, as fungicides have no curative activity against sclerotinia, Faye Ritchie, principal plant pathologist at ADAS, says. “Petals act as a nutrient source and also transfer spores down into the canopy, which is why fungicides need to be applied prior to petal fall and before any spores are present in the canopy, to be effective.”

Sclerotinia fungicides applied at the full recommended label rate will give approximately three weeks’ protection, Dr Ritchie says. “To get the most from a one spray approach to control this disease, it is best to apply fungicide as close to mid-flowering as possible - this will protect the crop as more petals fall into the canopy.”

But Bayer advises growers to consider a two-spray approach at high risk sites, where there is a history of severe slerotinia on farm, and/or the duration of flowering is extended, which it says could be the case in crops affected by cabbage stem flea beetle damage. It adds that the first spray can be applied prior to mid-flowering, with a follow up application no more than three weeks after that first application for continued protection.

Ms Crawford says: “A 75 per cent dose of Proline (prothioconazole) will provide effective protection for the first spray and can be followed up with another 50 per cent dose three weeks later where needed.”