Growers are being warned that they need to consider both Phoma stem canker as well as Light Leaf Spot when choosing their oilseed rape variety and planning their disease strategies.
Neil Groom of Grainseeds appreciates that Light Leaf Spot has been steadily moving southwards and has been increasing in incidence, but in large parts of England Phoma stem canker remains the top disease and growers’ attention should not be diverted away from it when choosing their varieties.
According to Crop Monitor in 2010, 78% of oilseed rape crops had Phoma stem canker whilst 71% had Light Leaf Spot. Regionally there were three large areas where Phoma still dominated – the East where 90% of its crops suffered from Phoma and 60% had Light Leaf Spot, the South West where 90% of crops had Phoma amd 67% had Light Leaf Spot and the Midlands and West where 88% has Phoma and 74% Light Leaf Spot. These three areas are where the national rape crop is predominantly grown.
Light Leaf Spot was more common last year in the North (52% of crops had Phoma and 90% Light Leaf Spot)and the South East where 64% of crops had Phoma and 71% Light Leaf Spot.
"Don’t underestimate Phoma - it will continue to be a problem. Already we have had the necessary 20 days of rainfall after the 1st of August to trigger the disease and we have many susceptible varieties being grown out there. These susceptible varieties may need two autumn fungicides if disease gets moving, with the first one potentially clashing with wheat drilling. Varieties with a disease rating of 7 or above to Phoma stem canker are easier and cheaper to manage, with the need for fungicide reduced. Resistant varieties appear to withstand the disease for longer allowing greater timing flexibility," says Neil.
"Experts are also saying that, with low levels of Light Leaf Spot control being achieved with current fungicide treatments, the use of resistant varieties is essential for this disease, too. Several varieties in the HGCA North List have high resistance ratings for Light Leaf Spot, but these same varieties have poor resistance ratings to Phoma. With the spread of Light Leaf Spot southwards and the spread of Phoma northwards, growers really need varieties with high disease resistance to both diseases."
"The low biomass variety Alienor has the highest combined disease resistance ratings of any conventional variety, with a 7.8 for Phoma and a 7.5 for Light leaf Spot, making it suitable to grow in all parts of the UK. The basis of Alienor’s resistance to Phoma is multigenic and so is long lasting," reports Neil.
For further comment and information on the oilseed rape variety Es Alienor or other Grainseed varieties such as Es Astrid or Es Cubic, please contact Neil Groom, Technical Manager Grainseed Ltd on 01379 871073 or 07774 720240.
