Brown Rot

Monilinia spp.

1. Identification

Monilinia spp. is a group of fungi responsible for important diseases in stone fruits and in pome fruits, known as brown rot, moniliosis or monilia. They affect flowers, branches and fruits, and can cause severe losses, especially under humid conditions during flowering and pre-harvest.

2. Causal agent

Ascomycete fungi of the genus Monilinia, described by Honey, characterised by the production of conidia in chains and by the formation of sclerotia or similar structures in mummified fruits.
The most relevant species include:

• Monilinia fructicola
• Monilinia laxa
• Monilinia fructigena

3. Main hosts

• Stone fruits: peach tree, plum tree, cherry tree, apricot tree
• Pome fruits: apple tree, pear tree
• Stored fruits may also be affected
  Each species of Monilinia shows a preference for certain hosts, but there is overlap.

4. Symptoms

• Flowers: necrosis, wilting and premature drop
• Young branches: canker and drying (“flagging”)
• Fruits: Brown spots that expand rapidly; Concentric rings of greyish or yellowish sporulation; Total rotting of the fruit; Formation of mummified fruits, which remain on the tree and act as a source of inoculum
• Post-harvest, rapid and destructive rots

5. Disease cycle

• The fungus overwinters in mummified fruits, cankers and plant debris
• In spring, it produces conidia that infect flowers and branches
• Secondary infections occur throughout the season, especially in humid periods
• Fruits close to ripening are highly susceptible
• The disease may continue to develop post-harvest, during transport and storage

6. Favourable conditions

• High humidity and rain during flowering
• Moderate temperatures (15–25 °C)
• Fruits with wounds caused by insects, hail or cracking
• High load of mummified fruits on the tree or on the soil
• High canopy density and poor ventilation

7. Disease management

• Removal of mummified fruits and infected branches
• Aeration pruning to improve air circulation
• Preventive protection with authorised products, especially at flowering and pre-harvest
• Maintenance of canopy health to reduce wounds and entry points
• Management of pests that cause damage to the fruits
• Post-harvest care: avoid wounds, maintain adequate storage conditions
• Less susceptible varieties, when available

Bibliographic references

• EPPO. Diagnostic Protocols for Monilinia spp.
• Agrios, G. N. (2005). Plant Pathology. Elsevier.
• FAO. Guidelines for Integrated Management of Fruit Rot Diseases.
• European Commission. IPM Principles for Stone Fruit and Pome Fruit.