Early start for sclerotinia germination

An earlier than normal start to sclerotinia germination in oilseed rape crops means growers need to watch disease risk closely as crops begin flowering, experts have advised.

According to monitoring by ADAS and BASF, sclerotia germination has already started at sites in Cambridgeshire and Norfolk. “This is unsurprising as crops are around four weeks earlier than last year and soil temperatures are rising,” said Peter Gladders of ADAS.

Sclerotia germination may increase rapidly once soil temperatures reach 10C, provided the soil surface is moist, he said. “The sclerotia then release air-borne spores which can then infect oilseed rape petals. Crops are at high risk if sclerotinia germination is synchronised with early flowering.”

BASF’s Diane Heath said it is generally too early to apply specific fungicides for sclerotinia control, but growers should keep an eye on how the disease progresses.

“Plant growth regulators such as Caramba (metconazole) are still being applied at the mid-extension stage and will top up phoma and light leaf spot control as well as reducing early sclerotinia infection by protecting the lower canopy.”

At early to full flowering, before disease symptoms are visible, she recommended applying Filan (boscalid) at 0.5kg/ha. The product also had activity against alternaria and botrytis and could be tank mixed with a pyrethroid insecticide if needed, she said.

Growers can monitor local disease risk using the BASF/ ADAS Sclerotinia monitoring service, available at www.totaloilseedcare.co.uk for the next twelve weeks. It can be used in conjunction with the HGCA Sclerotinia Decision Guide.