14 May 1999

Late season rape diseases to fore

OILSEED rape crops are fast moving through their key sclerotinia timings, so attention should now move to late season diseases instead.

Petal fall is already well under way in southern winter oilseed rape crops, which means the time for spraying against sclerotinia is nearly past, notes ADAS. Some untreated backward pigeon-hit crops and those further north with a history of the disease could merit attention with an mbc-based treatment, says pathologist Peter Gladders.

"But on the whole the balance is moving towards the need for more broad spectrum products like Compass and Folicur to deal with alternaria, especially where crops are lodging."

The current unsettled weather has increased the risk of alternaria and general moulds, agrees Liz Williams of CPB Twyford.

Grey aphids were starting to colonise crops in the recent warm spell, notes ADASs Jon Oakley. "But Id say dont panic. You need 10% of plants infected before the end of flowering to make treatment worthwhile." The warm weather will also have encouraged predators, he notes.

If considering a tank-mix growers should choose Aphox (pirimicarb) with added wetter, he advises. "They are hard to kill. A pyrethroid could just make matters worse." &#42