Integrate OSR disease control

OILSEED RAPE growers need to give more consideration to disease resistance when choosing varieties, according to a survey by BASF.

In the survey, 21% of farmers said general disease resistance was the number one characteristic they looked for, with 9% saying phoma resistance was important and 6% mentioned Light leaf spot.

But the majority said they treated all varieties the same when controlling diseases. “Oilseed rape should be treated more professionally in order to realise its true potential,” commented BASF’s Diane Heath.

Growers are advised to adopt an integrated approach, combining longer rotations, trash burial, resistant varieties, disease forecasts and fungicide thresholds.

“The risk of phoma will be higher this year as rotations have been tighter. This means more rape stubbles close to emerging rape crops, which will in turn, increase the risk of phoma infection,” she said.

Phoma leaf spot symptoms are already above threshold in a few crops close to last year’s oilseed rape stubbles, added ADAS’s Peter Gladders.

He advises growers to monitor crops closely and treat within two weeks of symptoms appearing.

“When 10 to 20% of plants show lesions, growers should be prepared to spray an appropriate fungicide. In varieties with lower disease resistance or smaller plants, the lower threshold should apply.”

Mrs Heath suggests using Caramba or Sunorg Pro (metconazole), which offer protection against phoma, light leaf spot and alternaria.