OILSEED RAPE growers are being urged to watch out for signs of phoma leaf spotting as spore activity increases.
Some leaf spotting has already been reported in high risk crops across Lincolnshire and the eastern counties, although no spore activity has yet been found in drier areas further west, according to Syngenta.
In mild weather growers will have around 7-10 days respite between spore infection and leaf spotting breaking out, so it is vital to act early, the firm warned.
“With increasing spore production over the last few days, and more rain forecast, Phoma leaf spotting is expected to keep increasing,” commented ADAS pathologist, Peter Gladders.
“It is imperative growers monitor crops carefully, particularly those close to last year’s oilseed rape stubbles.”
If the weather forecast suggests spraying conditions will be difficult, growers should treat at earlier signs of infection to avoid the risk of a severe attack, added Syngenta’s Beth Hall.
She recommends using Plover (difenconazole) and reducing treatment thresholds for small crops down to 10% of plants infected.
“Prioritise treatments on crops showing the greatest levels of leaf spotting, plants with the smallest leaves and the most susceptible varieties.”
Growers can monitor spore activity by registering for the Syngenta Phoma Advance Warning System (SPAWS), which is free to users of Plover. See www.syngenta-crop.co.uk