The AHDB has launched a beefed up sclerotinia risk alert service ahead of the oilseed rape flowering sprays, aimed at helping growers manage the disease.

Sclerotinia is a fungal disease that can reduce yields by up to 50% on affected plants and its control relies on well-timed preventative fungicide sprays.

To help farmers with their timings, the AHDB has improved its web-based service by using its WeatherHub page, which means many more sites can be included in the alerts. 

See also: Why OSR flowering sprays should be based on disease risk

The web tool uses a simple traffic-light system to highlight the UK areas where weather conditions are currently, or are forecast to be, suitable for the sclerotinia pathogen to infect crops. 

• Green = No infection risk alerts forecast
• Amber = Conditions forecast to come close to triggering infection risk alerts
• Red = Infection risk alerts forecast

Oilseed rape is at the greatest risk of infection when relative humidity is greater than 80% and air temperatures are at, or above, 7C for more than 23 hours.

Catherine Garman, who manages disease research at AHDB, explained that because fungicides are applied as a protectant, they should go on just before an infection risk alert.

“Going on earlier than this may increase the need for a follow-up treatment,” she notes.

She says the optimum timing for a single spray is, usually, just before mid-flowering on the main raceme and prior to significant petal fall.

“Persistence of full dose fungicides is about three weeks. If a spray is made earlier or if the flowering period is extended, a second spray may be required to protect the crop.”

Farmers can sign up at the AHDB’s dedicated webpage.