Asian brown rot

Monilinia polystroma is a pathogenic fungus responsible for Asian brown rot. This species is taxonomically related to other Monilinia species but exhibits distinct ecological and morphological characteristics. It is considered a serious quarantine-relevant pathogen in many regions, capable of causing devastating losses in stone fruit production.

The primary hosts of this pathogen include various stone fruits, with a strong focus on plums, apricots, peaches, and cherries. The fungus is not limited to the fruit itself; it can colonize blossoms and twigs, leading to blights. By attacking the floral organs, it effectively destroys the reproductive potential of the tree before the fruit even begins to set.

Symptoms are characterized by the rapid decay of fruit tissue, which turns soft and brown. Over time, the surface develops concentric rings of sporulation, which appear as yellowish or buff-colored cushions. On twigs, the infection results in a blight where the foliage appears scorched, often accompanied by the formation of cankers on the wood.

Environmental conditions that favor the spread of Monilinia polystroma include cool, rainy weather during the flowering period and high humidity during fruit maturity. The pathogen survives in the orchard as mycelium in infected mummified fruit, twig cankers, and debris. Insects play a significant role in spreading the spores and creating wounds that facilitate fungal entry.

Effective management strategy requires an integrated approach to reduce the inoculum levels and prevent infection:

• Rigorous sanitation practices, including the removal of all mummified fruits.
• Pruning and destroying infected branches to eliminate overwintering sites.
• Application of systemic and contact fungicides during critical growth stages.
• Pest management to minimize mechanical damage to the fruit skin, preventing fungal infestation.