Downy mildew alert in beans

AGRONOMISTS ACROSS England have found downy mildew on winter beans – a crop very rarely infected.

Growers have been warned to be on the alert for the disease which can spread rapidly and also damage spring crops.

“We‘ve had reports of 10-40% infection in crops from N Yorkshire to Essex,” said Farmacy technical manager Pam Chambers.

The level of infection is very variable, and has been seen in Clipper and Punch, but there is no information available on how susceptible varieties are.

“Mildew is often a problem in spring crops, but is very rarely seen in winter beans.”

The Processors and Growers Research Organisation said the disease had also been found in its winter bean plots.

The weather is believed to the problem, rather than a breakdown in varietal resistance.

“Cold nights, heavy dew and damp conditions mean infections are really taking off,” said Ms Chambers.

In spring crops a 25% threshold is needed to warrant control, she said, but growers often spray at first signs of mildew to check its rapid spread.

“Growers should look for a grey/brown growth on the underside of leaves.”

Folio Gold (metalaxyl-M + chlorothalonil) is the only product approved for use, although growers may consider mixing in a product to control chocolate spot.

“The recommended 2l/ha rate costs an arm and a leg. Growers may want to consider going in at 1l/ha with some Folicur (tebuconazole) and checking infection levels after 14 days,” advised Ms Chambers.

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