European brown rot

Disease

European brown rot

Monilinia laxa (Aderh. & Ruhl.)

Sclerotiniaceae: Helotiales

Distribution: Monilinia laxa is a plant pathogen that is the causal agent of brown rot of stone fruits.

Photos

Bark removed to show canker, gumming around dead spur. B

This rot is potentially serious on tart cherry cultivars Meteor, English Morello and Danube (Érdi bõtermõ) but rare on Montmorency. Wet periods lasting for a day or more are required for severe blossom infection and spur dieback. Newly infected blossoms and later spur leaves turn brown and shrivel. One- to 3-inch-long elliptical cankers, often with gummosis, are formed at the bases of blighted spurs. The fungus may produce tufts of ash-gray conidia on blossom debris, dead spurs and cankers in the second or third season after infection. Fruit infections are rare.

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.