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Start Phoma Control Programmes Now
Date added: 28/10/08 |
Oilseed Rape producers should start treating smaller crops and those with a lower disease rating before treating larger crops and those varieties with a higher disease resistance rating, advises ProCam Technical Director Dr. David Ellerton.
According to Dr Ellerton, this year is, once again, likely to be a high risk year for Phoma due to the wet August.
“Phoma risk is higher in the South than in the North, although the disease is creeping northwards,” he says.
“Growers will need to keep a close eye on their crops for the first signs of the disease and be prepared to spray quickly when the threshold of 10-20% of plants with symptoms is seen. Rapid reaction is required as we are relying on preventative rather than curative activity from most fungicides and the disease can build up very rapidly.”
Growers should also consider the size of the plants in order to prioritise treatments.
“The Phoma pathogen moves down to the leaf axil and to the stem much quicker in a smaller plant than a larger one. So if all crops require spraying, prioritise the smaller ones.
“Also prioritise those varieties with lower intrinsic disease resistance. This year’s variety split indicates that the majority of the area is down to varieties with medium Phoma disease ratings - between 4-6.”
ProCam’s 4cast database shows that Castille is the most widely grown variety this year and this has just a 6 rating against Phoma. The next most widely grown variety appears to be the hybrid Excalibur with just a 5 rating. But in the top six most popular varieties being grown, Excel has a 9 for Phoma and both Es Astrid and NK Karabik have a 7 rating.
“Treatments should be prioritised and varieties with the lowest ratings, and therefore the most vulnerable, should be sprayed first before those with a higher disease rating.”
Product choices include flusilazole (Genie), difenconazole (Plover), metconazole (Juventus) and prothioconazole (Proline), sys Dr. Ellerton.
“Juventus and Folicur (tebuconazole) have the best growth regulation effects. This year crops are divided into two types, either very forward or very backward and growth regulating fungicidal treatments should be used on the very forward crops.
“A two spray autumn programme provides optimum disease control and returns particularly if the autumn stays open. If the first spray has been applied in early October, the second should be planned for the end of November.
“I would expect persistence of 6 weeks with a good dose of these fungicides. Higher dose rates can increase persistence. For example using 0.8 l/ha of Genie instead of 0.4 l/ha provided an average 0.2 t/ha benefit, valued at £50 less the cost of the treatment.”
Ends
28th October 2008
For further information please contact Dr. David Ellerton, ProCam Ltd., Royston, Herts. Telephone: 01763 261592
Issued by Philip Hainey, Proterra Ltd., Stamford, Lincs. Telephone: 01780 756299
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