Pulsewatch: Disease alert after cold winter

Winter bean crops are showing signs of chocolate spot damage earlier this season because frost damage has allowed the disease to infect plants, warns the PGRO.

Anthony Biddle, PGRO technical director, says crop samples are showing signs of black leaf spotting, especially among earlier drilled crops.

“We’re seeing quite a lot of black leaf spotting on some of the older leaves on winter beans,” he confirms. “This is the cold weather effect, but the new growth which is starting to come away now looks reasonably clean.”

Chocolate spot could be a problem this season, he believes, although much will depend on the weather. “If it doesn’t rain, the disease won’t give us any problems, but if it does then it surely will.”

Fungicides are protectant, so they will not cure existing disease, but they can protect foliage where chocolate spot is developing on new growth. Growers should aim for a protective spray when buds start to show some colour, usually in the first or second week of May, Dr Biddle suggests.

For spring beans, drilling date appears to be determining the risk of downy mildew infection, Dr Biddle says. “There seems to be a two-way split on the drilling because we had a cold start and then a wet end to February,” he says.

“Crops that went in at the beginning of February could be at risk because they have been in the ground a long time and haven’t been growing very quickly because it had been cold.”

Looking at pests, Dr Biddle says pea and bean weevil are already “rampant” and there are signs of damage on winter and spring beans. “Temperatures have suddenly warmed up and it has been dry, so it has been ideal for weevils,” he explains.

Pulse Watch – take part and win an Apple iPad

In addition to Rust Watch, Septoria Watch and Sclerotinia watch, this year Farmers Weekly‘s Disease Watch service is also monitoring diseases in pea and bean crops, brought to you in association with BASF, Dalmark and Hutchinsons.

Go to our dedicated webpage and get the latest details of any diseases being observed in untreated varieties at various Hutchinsons and PGRO trials sites around the country. Take part in a mini-survey and you could win an iPad.


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