OILSEED rape growers planning to drill their crops in the second or third week of August this year are strongly advised to delay operations for a week or two - or to only use varieties with the highest resistance against stem canker (phoma), such as escort.

This advice comes from oilseed rape breeder at Nickerson (UK) Ltd, Dr Jo Bowman, who has been monitoring phoma in trials and commercial crops in England and northern France.

He said: "The level of the disease in both countries has been the highest for many years - some of this season's crops have been very badly damaged. The main finding is that crops drilled in the third week of August were badly infectd, while those drilled in early September had much lower levels of infection - even when grown in the same field."

Dr Bowman said the full extent of the disease only became apparent after this year's crops were swathed. Warning that the evidence from this year should be enough to delay drilling until after the third week in August, he added: "And because the potential carry over of disease from this year's crop is high, it would be wise to grow escort to ensure a clean start to the 2001 crop."