11 December 1998

Autumn mildew control advice

AVOID using access to kinder, longer lasting mildewicide quinoxyfen (Fortress) to justify spraying cereals for mildew in the autumn.

That is the message from Morley Research Centre researcher Doug Stevens. "The response to autumn mildew control has always been much less reliable than treating in the spring." Only thin, late sown crops on light land are ever likely to merit autumn treatment, he suggests.

When using morpholines there is a trade off between crop and disease damage, with strong signs that yield can be hit even where crops show no visible signs of spray scorch.

The more crop-friendly new chemistry could tempt growers to spray less severe mildew infections earlier, he admits. But in most cases doing so before the spring would be a mistake. "We still have grave reservations about spraying mildew in the autumn."

Early spring treatment however, before stem extension and the crop canopy closes over, is important to get the most from controlling mildew with quinoxyfen, he advises. In Morley trials it has lifted yields by nearly 0.5t/ha (4cwt/acre) over morpholines.