23 January 1998

Bad advice… big losses

BAD advice for controlling oilseed rape disease has seen growers suffer continuing losses, despite improvements in fungicide technology.

Stem canker and light leaf spot are the two most important diseases, causing combined losses of up to £80m a year, John Macfar-lane of ADAS Leeds told one of four farmer seminars held in conjunction with the conference.

The reason is clear when application timings are examined. Most crops are treated in March and April, which is too late for effective stem canker and light leaf spot control, yet too early for sclerotinia and alternaria, he said.

It is now accepted that the best approach is two half doses, one in the autumn and the other in the early spring.

At current prices, such a split programme would cost about £27/ha (£10.80/acre), excluding application. That equates to 0.15t/ha (1.2cwt/acre) of rape. "The yield increase required to cover the cost is fairly small," said Mr Macfarlane.