Increase of light leaf spot on oilseed rape in the United Kingdom

Date:09-01-2010


Oilseed rape light leaf spot varietal resistance is a critical factor for growers to consider this 2010 season. Trials suggest that fungicides only give up to 50 percent control of the disease, which in the 2009 season was found just about everywhere.
 
The black blotches on oilseed rape stubbles are next years inoculum, says Peter Gladders of ADAS [Agricultural Development and Advisory Service]. The only oilseed rape disease which showed an increase in prevalence compared with the previous season, light leaf spot has continued its spread to areas previously unaffected, he adds. "2010 was the 2nd highest year on record for light leaf spot, with 71 percent of crops affected," he reports. "Its the 5th year in succession that it has increased."
 
Although the north was the region with the highest incidence, with 90.5 percent of crops affected, the disease is now causing serious problems further south for two reasons, believes Dr Gladders. "The fungicides arent doing an adequate job, and the varieties being grown dont have good resistance." Thats in marked contrast to the varieties used in the north of England and Scotland. Trials suggest that varietal resistance is the key to controlling light leaf spot.
 
"The situation is serious. There was a great deal of light leaf spot in crops in 2010 -- it has overtaken phoma as the number one disease.

Warning bells should be ringing as levels have been rising steadily.

It can reduce yields by 1.5 t/ha."

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Source: Farmers Weekly Interactive [edited] <http://www.fwi.co.uk/Articles/2010/08/23/122992/Light-leaf-spot-leaves-its-mark-in-the-south.htm>