Light leaf spot risk highest in central Britain

AHDB’s light leaf spot (LLS) preliminary forecast shows that the disease risk to winter oilseed rape (OSR) is relatively high across central Britain.

The regional disease forecast highlights the proportion of OSR crops with a disease resistance rating of 5 predicted to have more than 25% of plants affected by the spring.

For southern England, risk is slightly higher than forecast during 2018/19 but remains relatively low.

Historically, risk is more serious toward the north of Britain. However, the 2019/20 forecast shows that the risk is moderate for much of Scotland.

Jon West, who manages the forecast at Rothamsted Research, said: “A relatively warm summer and low disease levels at the end of last season have driven down the light leaf spot risk across Scotland. In fact, you have to go back to the 2013/14 season to find a lower-risk year.

“Most of the Midlands, Wales and the north of England is forecast to be at a relatively high risk of this disease. However, this risk level could not be described as unusually high for these areas.”

The forecast can guide crop management decisions. For a more accurate picture of local risk, people can build a customised forecast via the AHDB website. This forecast also takes account of variety, sowing date and autumn fungicide applications.

For the strongest risk assessment, farmers should place leaf samples in polythene bags and incubate them at 10–15°C, for about five days, to bring out symptoms.

The preliminary forecast uses previous season pod incidence data and deviation from the 30-year mean summer (July/August) temperature data. In spring, an update to the forecast reflects deviation in winter rainfall from the 30-year mean.

Access information on LLS and fungicide performance via ahdb.org.uk/lightleafspot

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About The Author

John Swire - Deputy editor of Agronomist and Arable Farmer as well as responsibility for the Agronomist and Arable Farmer and Farm Business websites. After 17 years milking cows on the family farm John started writing about agriculture in 1998 and has since written for a variety of publications and has developed a wide circle of contacts within the industry. When not working John is a season ticket holder at Stoke City and also of late has become a fitness freak, listing cycling, swimming and walking as his exercises of choice.