First light leaf spot symptoms in OSR a month ahead of last season

Light leaf spot was identified on October 25, 2019 in Derbyshire and Angus, with samples later positively identified in the Scottish Highlands, Oxfordshire, Yorkshire and Norfolk.

According to Bayer, the results suggest there may be a lot of latent infection in OSR this autumn, which is expected to further develop if temperatures do not fall in the coming months.

The SpotCheck results to date do not come as a surprise to Philip Walker, ADAS arable plant pathologist, who cites above average rainfall in September and October as being a key driver of light leaf spot infections.

He says: “Last season initial infections were almost a month later (end of November 2018). Finding samples of light leaf spot so much earlier this season suggests there is a lot of latent infection in the crop, and we will see more and more symptoms developing if temperatures don’t drop in November and December.”

Ella Crawford, Bayer commercial technical manager for Suffolk, adds the SpotCheck results may be of particular significance for earlier drilled crops, which are at greater risk of light leaf spot infection.

“Oilseed rape crops remain a mixed bag, with many areas experiencing extensive flea beetle damage and being written off before incurring further input costs. However, there are a number of more forward, lush crops particularly those drilled early August. These crops will be at higher risk of light leaf spot infection, because the crop is exposed to ascospores for a longer period of time.

“In Suffolk, we are seeing phoma lesions on a large proportion of crops, and a small number of reports of light leaf spot symptoms. However, I would encourage growers and agronomists to utilise SpotCheck to understand the scale of latent infections and treat crops more effectively as a result.”