21 December 2001

Light leaf spot attacks OSR

OILSEED rape growers should check crops for light leaf spot and be ready to treat as soon as possible, says ADASs Peter Gladders.

"If you can see it, spray it, is the message at this time of year. The threshold of 25% of plants infected only applies in spring."

The disease was already present in crops at Boxworth, Cambs, a relatively low risk area, in mid-December. That should serve as a warning to growers further north where the disease usually causes more damage.

"The colder and wetter it is the more damage you get. The really serious yield loss occurs in the winter, up to 1t/ha."

Punch C (flusilazole + carbendazim) or Folicur (tebuconazole) should be used as soon as possible where infection is found. A spring follow-up treatment may still be needed.

If phoma re-infection is also present, which is probable in crops treated only once with fungicide this autumn, use Punch C. Where phoma is the only issue Plover (difenconazole) is an alternative. &#42