South: Phoma still poses oilseed rape yield loss risk

A drier spell of weather on the South Downs is allowing some field activity, but the colder nights and frosts aren’t helping the decisions to get on with remaining broad-leaved weed control in oilseed rape and spring grassweed control in cereals. However, there has been a lot of “spraying off” of stubbles for spring seed-beds and some drilling has taken place on the lighter soils.

Above average winter temperatures mean it probably still hasn’t been cold enough to reliably finish off any lingering aphids in cereals or oilseed rape and they can still be found in some sheltered fields of winter cereal crops; if BYDV control was compromised last autumn or it has been some time since the last insecticide was applied, take any opportunity to top-up the protection. Despite this current cold snap, cereals are very forward for the time of year, with some requiring an early plant growth regulator application. Any frosts we get from now on will help slow the continued advance of yellow rust and mildew, which is very obvious in many wheats.

In oilseed rape. phoma and light leaf spot reinfection is occurring and can be readily found in many crops, with the with the exception of very resistant varieties. Where plants are very small and heavily infected, a second phoma spray will be justified in mid-February because the risk of yield loss remains high. A prochloraz/tebuconazole mix applied now, followed up with Toprex (paclobutrazol + difenconazole) at stem extension will be called for. However, as many larger crops are already moving rapidly into stem extension, that may be that the starting point of the spring fungicide program.

As spring approaches it marks the end of some very inspiring technical meetings attended over the winter. Last week saw Biodiversity Agriculture and the Environment (Base) hold their AGM at Stoneleigh Park, Warwickshire. An international range of speakers highlighted once again the huge benefits of improving soil organic matter levels and focusing more on improving soil biology through minimal soil disturbance. While a long term goal, the change to better water infiltration rates and nutrient use efficiency that adopting conservation agriculture techniques can bring cannot be underestimated.

NOVEMBER
3

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