Oilseed rape growers are being advised to consider applying a fungicide with growth regulatory properties this autumn to control crop canopies and minimise the risk of phoma.
Some early-drilled crops already have strong actively-growing canopies of 4-6 leaves.
Jon Williams, agronomy manager for BASF, says using a PGR fungicide, such as metconazole, this autumn could be a good option, especially as disease is likely to be high.
“Research work by ADAS has shown that small canopies produced the best yields and the autumn is where you start manipulating the plants to optimise these canopies,” he says.
“Sunorg Pro (metconazole) offers both good disease protection against phoma stem canker, with some activity on light leaf spot, plus the all important first steps in canopy management.”
Growers should monitor crops for phoma, looking for the threshold of 10-20% of plants showing at least one lesion, and be prepared to spray within two weeks of the symptoms appearing.
Peter Gladders of ADAS has warned growers that there is a potentially high risk of phoma stem canker this year.
Dr Gladders reminds growers how phoma came in quickly last year, moving into crops from 0 to 100% infection in just one week in early October. He expects a repeat situation this year.
“We have already exceeded the necessary rain events for phoma risk, particularly in the east of England,” says Dr Gladders.
“Spores of phoma can be produced from rape stubbles when there are 20 days with rain from 1 August.
“With many susceptible varieties being grown plus the lack of eradicant fungicides, there is a need to plan for two autumn fungicides and protect the profit potential of this key crop.”