15 May 1998

Beans face up to twin threats

By Andrew Swallow

BEAN growers need to get fungicides onto untreated crops soon and avoid rate cutting to combat widespread ascochyta and fast developing chocolate spot.

Weather conditions will determine which disease is most prevalent, says Anthony Biddle of the Pulse Growers Research Organisation.

"Unless it gets very hot, dry and sunny, one or the other disease is likely to be a problem. Frequent rain and spore splash favours aschochyta, whereas chocolate spot will develop rapidly in dull humid conditions."

But aschochyta control relies on protective treatments, so protection from this disease is the priority when formulating tank-mixes, he says.

"Growers should stick with chlorothalonil-based tank mixes and make sure a full 2.0 litre/ha is applied. Do not be tempted to reduce rates as we have done in past years. Disease pressure is much higher this year."

Bob Mills of Banks Agriculture agrees chlorothalonil is required where ascochyta is still present, but sees chocolate spot as the main threat.

"Ultimately chocolate spot is more threatening than ascochyta – carbendazim plus chlorothalonil should be used to keep on top of it. But if growers are chasing the disease hard an iprodione based product such as Compass at 3.0l/ha should be used."