Growers put on the alert as Light Leaf Spot moves south

There is growing evidence to show Light Leaf Spot (LLS), which causes severe damage to oilseed rape crops every year, has escaped the confines of Scotland and the north England to attack crops in the south.

This is revealed in the latest Rothamsted Research "risk forecast", which shows the percentage of crops with more than 25% of the plants infected with LLS in the South West in 2008/9 was 64%, compared with 27% in 2008, 25% in 2007 and 15% in 2006.

There is a similar picture in East Anglia, where the incidence of the disease has rise from 5% in 2006 to more than 12% this year. In Scotland, however, the incidence has fallen from 76% in 2007 to 48% in 2008/9

Growers in the south are being urged to spray crops to control the disease in late November/early December and repeat the treatment at early stem extension - and this year they will have an alternative high quality tebuconazole fungicide to choose from: Rotam’s new Toleda.

"Specially concentrated and with a high level of activity and crop safety, Toledo’s key benefits at the autumn spray timing are targeted light leaf spot control and manipulation of the canopy structure, to help ensure the optimum leaf area for light interception as the crop moves into the spring growing season," said Graham Dickinson, Rotam’s Regional Manager for the UK and Northern Europe.

First indications of Light Leaf Spot are usually seen as large mealy blotches with a pinkish white centre and white spore droplets around the lesions in late November. By spring, plants heavily infected plants could be stunted and will produce weak growth at stem extension, with secondary spread occurring throughout the life of the crop.

Mr Dickinson pointed out that action to control the plant disease was vital because it could cause yield losses of up to 1.5t/ha, at an estimated cost of between £15 million and £39 million a year.