Chocolate spot threat for winter beans

Growers of winter beans should watch for chocolate spot amid increasing reports of the disease damaging plants, warns the PGRO.

Becky Ward, PGRO senior technical officer, says a high level of chocolate spot has been found on plants sent in to PGRO so far this year.

The increase is partly because the harsh winter has left plants more susceptible to infection from trash left behind from last year’s crops, she suggests.

“The harsh weather conditions experienced over the winter have caused winter crops of beans to suffer some physical damage from frost and wind.

“Where this has been severe, leading to stunting and plant death, surviving plants have become much more susceptible to disease infection.”

Symptoms include the blackening of stems or lower leaves and the emergence of chocolate spot lesions which can kill off the plant completely.

Miss Ward says fungicides cannot eradicate any existing disease but can protect infection from spreading.

“There are plenty of products available for use on chocolate spot,” says Miss Ward.

“Some contain the active ingredient chlorothalonil which can either go on to the crop straight or with mixes.”

The disease has been identified on plants from Herefordshire, the midlands and the south-west but it does not appear to be confined to any specific area, notes Miss Ward.

Picture: Syngenta

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