|Chocolate spot on broad bean leaves|
|Species:||Botrytis cinerea and Botrytis fabae|
Chocolate spot is caused by two Botryotinia fungi; Botrytis cinerea affects crops intermittently, and is usually confined to flowering whilst Botrytis fabae is prevalent throughout the season. B. cinerea is more virulent, producing a 3% reduction in yield per percent disease infection whilst the mean yield loss from B. fabae is 0.5% per percent disease infection.
Disease infection appears as dark brown lesions, which enlarge and coalesce, usually occurring on the lower leaves first, moving to the middle and then upper canopy. Disease growth is optimal when temperatures of 15°C (59°F) and relative humidities of more than 85% predominate. Chocolate spot is generally associated with wet seasons and dense crops. Field beans in common with most pulses supply the assimilates for seed growth at each node from the leaves subtending that node. Thus, a strong relationship exists between disease infection in the podding region and seed yield.
- Chocolate Spot - Botrytis cinerea and Botrytis fabae. Winter beans - Wherry & Sons Ltd.. Retrieved: 2010-08-04.