Diplotheca tunae

Diplotheca tunae is a fungal disease classified as a pathogen that primarily affects succulent plants. The causative agent belongs to the Ascomycota division and specializes in the tissues of cacti, causing necrotic processes in the stems. In phytopathological terms, this disease is considered a highly specialized parasite.

The main crops susceptible to infection are members of the Cactaceae family. The disease is particularly severe in various species of the genus Opuntia (prickly pear). In private collections and specialized greenhouse environments, the pathogen can spread rapidly between neighboring specimens if they are kept in crowded conditions.

Symptoms of the disease manifest as the formation of rounded or irregular spots on the surface of the cladodes. As the disease progresses, the affected areas become sunken, take on a brown or gray hue, and the tissues beneath them begin to soften. Often, a characteristic margin can be observed around the edges of the spots, indicating active expansion of the mycelium into healthy plant tissues.

The development and spread of the infection are facilitated by high humidity, poor air circulation around the plants, and the presence of micro-injuries on the succulent epidermis. A temperature range of 20–25°C (68–77°F) is most favorable for the active sporulation of the fungus. Spores are dispersed through airborne droplets, contaminated pruning tools, or by pests that damage the plant's surface.

The damage caused by Diplotheca tunae involves the systemic weakening of the cactus's immune system and the potential for total plant death if left untreated. To combat the disease, the following measures are recommended:

• Prompt isolation of infected specimens from the healthy collection.
• Surgical removal of diseased tissues, including a margin of healthy tissue.
• Treatment of cuts with antiseptics (crushed charcoal, sulfur).
• Application of systemic fungicides containing copper or specialized anti-fungal agents.
• Normalization of irrigation and improvement of greenhouse ventilation to reduce humidity.