Monilinia laxa

Monilinia laxa is a filamentous ascomycete fungus that belongs to the genus Monilinia. It acts as a primary phytopathogen, causing significant damage to stone fruit crops. As a specialized pathogen, it focuses its life cycle on the vegetative and reproductive parts of plants within the Rosaceae family.

The primary hosts for this fungus include apricot, cherry, sour cherry, plum, and peach. The disease manifestations are characterized by blossom blight, which occurs during spring and leads to the sudden wilting and necrosis of flowers and shoots, and brown rot, which develops on ripening fruit as soft, decaying areas covered in greyish tufts of fungal spores.

The lifecycle of Monilinia laxa involves overwintering as mycelium in cankers on twigs or in mummified fruits remaining on the tree or the ground. Upon the return of favorable conditions in spring, the fungus produces conidia. These spores are dispersed by rain splash, wind, or pollinating insects, landing on floral organs and initiating infections by penetrating through the stigma or style.

Environmental conditions play a crucial role in disease epidemiology. Prolonged wet weather accompanied by moderate temperatures during the flowering period is optimal for the infection process. Later in the season, high humidity and temperature promote the development of brown rot, especially if the fruit surface has been compromised by insect stings, hail, or mechanical injury.

The economic impact of this pathogen is severe, often resulting in massive yield losses and weakened tree structure. An integrated pest management approach is essential for control:

• Pruning and removing infected branches to reduce the inoculum load.
• Strict sanitation by removing and destroying mummified fruit from the orchard.
• Application of copper-based fungicides during the dormant season.
• Timing systemic fungicide applications during the bloom stage for maximum efficacy.
• Monitoring and controlling insect vectors that physically damage fruit and facilitate spore entry.