Wet weather sees earlier reports of light leaf spot in OSR

The first signs of light leaf spot have been reported in oilseed rape crops, suggesting there could be a lot of infection in crops which will develop further if temperatures remain mild in the coming months.

Light leaf spot was first identified by the SpotCheck testing service in Derbyshire and Angus, with samples later positively identified in the Scottish Highlands, Oxfordshire, Yorkshire and Norfolk.

This is a month earlier than initial reports last year.

The results do not come as a surprise to plant pathologist Philip Walker, at ADAS, who says the above average rainfall in September and October is a key driver in light leaf spot infections.

“Moisture, and particularly leaf wetness, is very important to light leaf spot infection occurring. For infection to occur there needs to be a minimum of six hours of leaf wetness, and as those hours of leaf wetness increase, so too does the likelihood of infection.

See also: How to tackle light leaf spot in OSR

He points out that finding samples of light leaf spot so much earlier this season suggests there is a lot of latent infection in the crop.

“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 note for earlier drilled crops, which are at greater risk of light leaf spot infection.

Growers can take advantage of Bayer’s free SpotCheck initiative by visiting the dedicated website.