Late autumn OSR treatments to bolster LLS activity
Autumn oilseed rape fungicide programmes that have hitherto been primarily aimed at Phoma protection with Plover, should now increasingly look to bolster Light Leaf Spot activity too.
The latest Phoma Alert disease tracking records (below) show that the majority of untreated varieties on the three ADAS monitored sites have above treatment threshold levels of leaf spotting and in need of treatment.
As the season progresses, the risk of Light Leaf Spot also becomes greater and can be usefully controlled in tandem.
Frontier agronomist, Jeremy Ruff, has warned that high humidity and almost permanently wet leaves in this season’s dense crop canopy could create the ideal conditions for Light Leaf Spot development in late autumn.
Jeremy Ruff of Frontier Agriculture (above, right) advocated oilseed rape growers should be increasingly looking at strengthening Light Leaf Spot control as the season moves into the late autumn and winter.
Speaking at a recent iOSR grower group meeting in Lincolnshire, he highlighted that where growers had been targeting Phoma with early autumn fungicide applications, as the season progresses into November, greater emphasis should be on bolstering LLS protection, typically adding tebuconazole to Plover treatments.
“There is little or no curative activity for Light Leaf Spot, so the priority has to be on early prevention to stop disease getting established,” advised Jeremy Ruff.
“Once it’s in a dense crop it will continue to cycle and develop, especially over another mild winter.”
Jeremy pointed out that while varietal resistance may help slow development of disease within the crop, plants are still susceptible and will be using energy to fight infection – which is better dealt with by a fungicide programme.
“With Phoma, the resistance rating is based on a score of stem cankers in the spring, not leaf infection in the autumn," he said.
"Growers should be using varietal resistance as a guide for managing crops and prioritising treatments.”
Syngenta iOSR grower group on the Lincolnshire farm of Sutton Estates, with Head of Farming, Chris Baylis (above, far left).