Diplodia Dieback

Diplodia dieback, caused by the fungus Diplodia cacaoicola (syn. Botryodiplodia theobromae), is a destructive plant disease characterized by tissue necrosis and branch dieback. The pathogen is a facultative parasite, meaning it can thrive on dead organic matter before invading living hosts under favorable conditions.

This fungus affects a diverse range of commercially important species including cacao, mango, avocado, papaya, poinsettia, linseed (flax), and various orchids like Cattleya. In perennial trees, the infection often leads to severe yield losses and, in extreme cases, the total death of the tree.

The characteristic signs of the disease include sunken necrotic areas on the bark, longitudinal cracking, and wilting of the foliage. Close inspection often reveals the presence of numerous small, black pycnidia breaking through the epidermal layers of the bark. These structures release spores that spread the infection throughout the plantation.

Disease progression is heavily influenced by environmental stress, particularly high temperatures and high relative humidity. The fungus typically enters the host through pruning wounds, insect feeding sites, or natural openings. Poor plantation management, such as lack of sanitation or inadequate spacing, significantly increases the spread of the pathogen.

Management strategies focus on integrated pest management (IPM). Key actions include:

• Strict sanitation by pruning and destroying infected branches.
• Sterilization of pruning tools to prevent mechanical transmission.
• Application of copper-based fungicides to protect vulnerable stems.
• Maintaining plant vigor through proper nutrition and irrigation.