21 January 2000

Phoma advice on offer

BIG differences between phoma levels in autumn fungicide-treated Pronto oilseed rape are showing at NIAB sites, highlighting a need for individual crop monitoring.

At the Cambs site, where the crop is relatively small, 53% of plants had leaf spots with some showing on upper leaves by Monday. "In these circumstances a second spray sooner rather than later is advisable, if it can be done," says pathologist Jane Thomas.

However, in trials in Kent and Hants infected lower leaves have dropped off and there is little sign of re-infection further up. The crop is quite large so further treatment could be postponed, she says.

In Notts, phoma is more apparent but mostly confined to lower leaves of a large crop, so retreatment can be left to late January or early February, she suggests. &#42