Monday, December 10, 2018

Risk forecast to guide sclerotinia spray decisions on rape

April 3, 2018 by  
Filed under Crops

Regular  sclerotinia forecasts – which flag up when oilseed rape crops are at risk from infection – are now available from the AHDB website.

Based on actual and forecast weather, the map-based tool indicates the infection risk level at 15 sites. Data can be used to focus monitoring efforts and guide the application of protectant fungicide treatments to prevent or limit infection during flowering.

Rape is at the highest risk of infection when relative humidity is greater than 80% and temperatures are at or above 7C for more than 23 hours. A simple traffic-light system is used to indicate the infection risk level at each site (see below).

Regularly updated

The 15 sites used in the 2018 forecasts stretch from south-west England to the Scottish Borders Updated every Monday, Wednesday and Thursday, they include a number of sites across the Midlands and East Anglia.

ADAS forecaster Caroline Young said:  “Infection risk information is vital for the control of sclerotinia, as fungicides have little or no curative activity and should be applied ahead of infection.

“The forecasts show if there’s been an infection alert in the previous 24 hours or if there’s likely to be an infection alert in the next 48 hours.

“If spores are present, they can germinate and infect for a day or so after an alert. So, if a spray can’t be applied in time, it should still be applied as soon as possible after the infection alert because there will still be a benefit, albeit a diminishing one.”

Applications

Treatments against sclerotinia include Amistar from Syngenta. Applications are best targeted to coat petals with spray, but also with sufficient water volume and using angled nozzles to achieve penetration of the canopy and provide a protective coating throughout the plants.

Commentary on the AHDB website will pull out key trends and regional hotspots. Information on other key risk factors – including crop growth stage, spore pressures, sclerotial germination progress and results from petal tests – will also be presented, when possible.

Information on disease pressure is particularly important, as an infection alert only counts if spores are present.

Forecast information can be accessed via cereals.ahdb.org.uk/sclerotinia

Traffic light infection risk

Red
23 hours or more of continuous infection conditions

Amber
21 to 23 hours of continuous infection conditions

Green
Less than 21 hours of continuous infection
conditions

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