21 November 1997

Is your rape phoma-free?

PHOMA levels in rape are rocketing following unseasonably mild conditions. Advisers are urging growers to check crops and spray where thresholds are exceeded.

Infections have gone from trace to 30% in a few days, says ADAS. Small, green lesions mean particular care is needed when walking crops this season, it adds.

Already exceeded

Crops with 10-20% infected plants should be sprayed, advises ADAS. If that threshold is already exceeded choose products with curative kick-back action, containing deifenoconazole (Plover) or flusilazole (Punch C, Sanction Genie).

Up to 40% of crops are protected already, reckons Andy Selley of fungicide manufacturer Du Pont. But untreated crops need treating now.

Indeed, very advanced crops of varieties with phoma as their main weakness, like hybrids, could benefit from a very early second spray. "Spraying at the end of December could be worthwhile."