Wet conditions increase chocolate spot risk

A two-spray fungicide programme may prove a good investment for pulses this season, as the current wet weather increases the risk of chocolate spot this season.

Chocolate spot (botrytis) risk is likely to be high as temperature and humidity rise, says Ian Holmes Syngenta field technical manager. Symptoms include the blackening of stems or lower leaves and the emergence of chocolate spot lesions that can kill off the plant completely.

Last year PGRO trials were carried out comparing a range of fungicides on winter bean crops it showed that a 10% increase in yield was possible with a two fungicide spray programme. This was achieved through the enhanced control of chocolate spot and rust.

A two-spray approach on a crop of Wizard beans reduced overall disease levels from 44% in a one spray programme to 21% using a two-spray strategy.

Rust incidence can be halved through a single treatment at early flowering stage; a second fungicide application around four weeks later with more than 50% of pods at final length can virtually eliminated the disease, said Mr Holmes.

However, he advises that before growers decide on their fungicide programme they need to understand the most cost effective options.

“Although some products showed similar yield responses the relative costs ensured that Auto Elite (chlorothalonil and cyproconazole) produced the greatest margin over input cost at around £29/ha,” he said.

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