Danger of chocolate spot and rust infections

Growers are being urged to keep an eye out for chocolate spot and rust infections due to the contrasting weather conditions recently.

With wet weather bringing an abrupt end to a long period of dry, almost drought-like conditions, growers are being urged to protect beans from chocolate spot and rust infections.

The warning has come from crop protection company Adama and their fungicide expert, Andy Bailey, cautioned wetter weather could put both winter and spring bean crops at risk of infection from bean chocolate spot (Botrytis spp).

“Winter sown beans are typically protected against chocolate spot with a two-spray programme starting at the early flowering stage, usually in early May,” said Mr Bailey.

“This year the weather was dry during that period so crops weren’t under too much pressure.

“For spring beans, fungicide treatments are yet to get under way, but that doesn’t mean growers should be complacent – the onset of wetter conditions could spell trouble as there is an increased potential for the disease to develop in both crops.”

Mr Bailey also warned bean crops could come under pressure from rust infections once any wetter weather period is followed by a temperature rise.

Chocolate spot is caused by two species of the fungus Botrytis.

Botrytis fabae is the most common cause and only affects broad beans; while Botrytis cinerea, which can cause very similar symptoms, also causes grey mould on a wide range of plants.

Chocolate spot can be damaging, in some cases causing flower loss, with severe attacks resulting in whole plant collapse.