American brown rot

Disease

American brown rot

Monilinia fructicola (G. Wint.)

Sclerotiniaceae: Helotiales

Distribution: Widespread; common to all fruit-growing regions in eastern North America.

Photos

Dieback of peach shoot tip from brown rot; note sporulation. C

American brown rot is common on apricot, peach, nectarine, plum and cherry. On fruit, small, circular, light brown spots enlarge rapidly to rot the whole fruit pre- and post-harvest. Rotted fruit shrivel, eventually becoming mummified. Infected blossoms wilt, turn brown, shrivel and persist into summer.

Oval sunken brown cankers develop at the base of infected blossom spurs and fruit of peach, nectarine and apricot; later, the bark at the edge of the canker cracks, gum oozes out and a callus forms.

Ash-gray tufts (sporodochia) bearing conidia of the fungus often develop over the surface of the infected tissues. The presence of conidia on lesions is the most distinctive characteristic of brown rot.

Crops Affected: cherries, peaches, plums

Management

Prune out mummified fruit and cankers during the dormant season and burn or bury them deep in the soil. Remove wild or neglected stone fruit trees in the area that may serve as reservoirs for disease. Fungicides should be applied during bloom if warm (> 18Â°C) rains are predicted, especially in orchards where inoculum levels are high. Fruit are very susceptible to infection 1â€“3 weeks after shuck split and again from 3 weeks prior to harvest through the harvest period. Fungicides are often used during these periods to protect fruit.

Similar Species

Blossom blight can be confused with blossom blast caused by Pseudomonas syringae van Hall; fruit rot can be confused with Alternaria fruit rot and Rhizopus rot. The presence of fungal sporulation helps to differentiate the different diseases. Brown rot-infected fruit will produce powdery gray to light brown spores, whereas Alternaria-rotted fruit will develop a dark green to brown mass of spores. Rhizopus-infected fruit develop a softer rot than brown rot-infected fruit. Also, Rhizopus produces "whisker-like" tufts of grayish-white sporangiophores capped with a black spore mass at their tips; the sporangiophores can exceed 1 cm in length.