The latest Rothamsted light leaf spot (LLS) forecast once again has Wales and the West of England bearing the brunt of the disease. This season the >25% affected plants figure is 80% - only equalled by established northern ‘hot spots’.
Since 2010 losses to LLS have been in excess of £80m per year, and it has jumped the disease to thenumber one threat in a very short time. In that period Wales and the West of England has often been hit hard – last season >25% affected plants for the region was 89%, again comparable with northern areas.
Bayer’s Tim Nicholson isn’t so surprised though. “A key driver for the disease is rainsplash at the asexual stage. With rainfall splashing spores about it is no surprise to see the risk for Wales and the West of England region similar to levels for the north and Scotland.”
Which is why he is advising growers to think carefully about sprays going forward. “The OSR area is down this season but not as much as originally forecast, the disease has come through a mild winter and growth regulation will be a factor in some stem extension sprays. Many of these PGR products are poor against the disease so a subsequent active at flowering effective against both Sclerotinia and LLS wouldn’t be a bad idea, and there is none better than Proline275 (prothioconazole). Where no PGR is required then prothioconazole remains the natural choice for light leaf spot control.
“What is critical is to stop LLS spreading through the canopy and onto the pods as split pods could have a catastrophic effect on yield and oil content,” he warns.