Overall light leaf spot risk remains relatively low

Light leaf spot (LLS) risk has remained relatively low, according to the spring update of the 2018/19 forecast.

Each spring, the autumn forecast is updated to take account of winter rainfall. As January and February were relatively dry, and because December was not particularly wet, the overall risk has reduced in the final forecast.

The regional forecast highlights the proportion of the winter oilseed rape (OSR) crop, with a disease resistance rating of 5, predicted to have more than 25% of plants affected by the disease by the spring. The forecast does not show total incidence.

Jon West, who manages the forecast at Rothamsted Research, said: “Light leaf spot symptoms have already been observed at some monitoring sites. Although it is a relatively low-risk year, a high incidence can still occur in some crops.

“February got off to a cold start and this favours disease development. This was followed by unusually dry, sunny weather towards the end of the month and this favours symptom expression.

“As there is always a lot of field-to-field and within-field variability, we advise vigilance and frequent crop inspections to assess LLS severity.”

It is the first season since 2013/14 that no regions have fallen into the highest risk category (>60%).

Towards southern Britain, especially in East Anglia, the risk forecast is exceptionally low, with the forecast predicting even lower disease pressures than the relatively low-risk 2013/14 season.

Historically, LLS risk is more serious towards the north of England and in Scotland. The 2018/19 risk in these regions can be described as moderate. The highest risk is forecast to be in the West Midlands and Wales regions.


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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.