Stuck in a rut: Light leaf spot loves valley life

This week, I have been lucky enough to be shown around an oilseed rape Recommended List trial by oilseed rape expert and plant breeder, Mark Nightingale from Elsoms. We were at a site in Harlaxton, Lincolnshire, in a valley which is known for having high levels of light leaf spot.

Part of the reason for the recurring high levels of LLS is the valley’s ability to hold moisture, creating ideal conditions for sporulation of this disease. The cool and wet winter and spring this year has meant these ideal conditions have been prevalent across the UK, leading to high levels of LLS across the country. This is compounded by LLS resistance to azoles, leading to frequent reports of poor control by fungicides.

Recent rainfall events have caused rain-splash of LLS up the canopy to newly emerged leaves.

We saw evidence that this disease is already progressing up the plant where it could reach the pods if conditions remain conducive, with ‘laddering’ of the disease up the stem.

Petals had already started dropping and sticking to leaves, creating a food source for sclerotinia to germinate and infect the crop.

Other observations of the crop included stems of some varieties forming an ‘S’ shape due to the frosty weather we’ve been having.

There was also fasciation of the stem in some varieties, where there appears to be two stems with a ridge down the middle. This is not a desirable characteristic, so there are limits on the number of fasciated stems that a variety is allowed.

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Catherine Garman

Catherine Garman

Catherine is Crop Health & Protection Scientist (Diseases) at AHDB

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