Tamarillo anthracnose

Initial symptoms are characterized by small, circular, water-soaked spots on the surface of developing fruits. These lesions gradually enlarge and become dark, sunken, and necrotic.

As the infection progresses, the center of the lesion develops characteristic concentric rings. These are often covered by a mass of spores, which may appear pinkish, orange, or black depending on the humidity levels.

Leaves may exhibit irregular brown spots with chlorotic haloes, which can lead to premature leaf drop. Severe infections on stems appear as sunken ulcers, potentially causing the dieback of fruit-bearing branches.

Fruit decay is the most visible sign of the disease, rendering the produce unmarketable and inedible. The internal flesh of the fruit beneath the necrotic spots often becomes soft and mushy.

Careful monitoring is essential, especially during wet weather, to detect early signs of infection. Scouting the orchard helps in pinpointing hotspots before the disease becomes widespread across the crop.

Tamarillo anthracnose is caused by the fungus Colletotrichum tamarilloi, an ascomycete pathogen that specifically affects the tree tomato crop. It is known for its ability to cause severe fruit lesions during the ripening stage.

The life cycle of this fungus relies on the production of conidia within acervuli. These spores are spread primarily by water splashing, wind, and movement of contaminated tools or workers within the orchard.

The fungus penetrates the cuticle of the host plant by secreting specialized enzymes that degrade plant cell walls. Once inside, the hyphae spread rapidly through the tissue, absorbing nutrients and causing structural collapse.

Under favorable environmental conditions, the fungus produces a second generation of spores within a few days. This allows the disease to propagate throughout the entire canopy, leading to rapid infection spread.

Surviving in the soil or on infected plant debris, Colletotrichum tamarilloi remains a constant threat. Dormant stages of the pathogen ensure its persistence from one season to the next, necessitating rigorous management.

The development of Colletotrichum tamarilloi is highly dependent on high atmospheric humidity and frequent rainfall. Moisture on the fruit surface is essential for the germination of fungal conidia.

Temperatures ranging from 20°C to 25°C are ideal for rapid colonization of host tissues. In these conditions, the incubation period is significantly shortened, increasing the risk of an epidemic.

Poor ventilation within the orchard, caused by overcrowding or lack of pruning, creates a humid microclimate. This environment allows the pathogen to thrive and move between trees more easily.

Overhead irrigation systems are major risk factors for disease spread, as they mimic rainy conditions and distribute spores to healthy plant parts. Drip irrigation is highly recommended for disease management.

Lack of proper field sanitation contributes to the buildup of inoculum in the soil. Decaying plant material provides a substrate for the fungus to multiply when the host plant is not actively growing.

The economic impact of tamarillo anthracnose is severe, often resulting in significant yield losses. Growers can lose a high percentage of their harvest due to fruit rot and premature dropping.

Post-harvest losses are also a critical issue, as infected fruits may appear healthy at harvest but develop visible lesions during storage or transit. This reduces the shelf life and quality of the produce.

The disease weakens the tree's health, leading to decreased vigor and overall yield potential for subsequent seasons. Persistent infection can eventually lead to the loss of entire tree stands.

Additional costs for chemical control measures, including fungicides and labor, increase the production cost of the fruit. This makes the crop less profitable and less competitive on the market.

In regions where this pathogen is established, it can become a limiting factor for expansion. The necessity for strict disease management practices adds a layer of complexity to farm operations.

Sanitation is the cornerstone of control. Regularly removing and destroying infected plant parts prevents the buildup of fungal spores in the orchard environment and limits disease spread.

Proper pruning and orchard design ensure good air circulation, which helps dry the canopy faster after rain. This reduces the duration of moisture presence required for fungal infection.

Chemical protection with registered fungicides is effective when applied preventively. It is important to alternate between different chemical groups to prevent the development of resistant fungal strains.

Selecting and breeding for resistant tamarillo varieties is the most sustainable approach to long-term disease management. Research is ongoing to identify genotypes with natural immunity to C. tamarilloi.

Integrated Pest Management (IPM) practices combine cultural, biological, and chemical methods to minimize impact.

• Monitor fields for early signs of symptoms.
• Ensure balanced soil nutrient levels.
• Clean tools after use in infected areas.