Feijoa anthracnose

Initial symptoms include the appearance of small, water-soaked spots on leaves, which gradually enlarge and turn dark brown or black with a distinct margin.

In highly humid conditions, the centers of these lesions produce characteristic pinkish or creamy spore masses, which are a definitive sign of anthracnose.

Fruit symptoms manifest as sunken, dark lesions that may expand, eventually causing the fruit to rot or drop prematurely from the tree.

Twigs and young shoots may develop elongated lesions or cankers, which can lead to dieback of the branch tips if the infection becomes systemic.

Severe infestations often result in widespread defoliation, leaving the tree weakened and susceptible to further environmental stress.

Feijoa anthracnose is caused by the fungus Colletotrichum feijoicola, which is a specialized pathogen targeting Acca sellowiana and related Myrtaceae species.

The fungus survives as mycelium or dormant spores within infected plant debris, twigs, and mummified fruits left on the tree throughout the dormant season.

Under suitable conditions, conidia are produced and spread to healthy tissues primarily through rain splashes, irrigation runoff, and movement of infected tools or wind.

The pathogen is highly aggressive in warm, humid climates, where it can complete its life cycle rapidly and generate multiple infection cycles during one season.

Genetic studies indicate that this specific strain of Colletotrichum has evolved to overcome the natural defenses of the feijoa plant, making it a persistent challenge.

The development of feijoa anthracnose is strongly linked to high moisture levels, particularly persistent dew, fog, or frequent rainfall during the growing period.

The optimal temperature range for the pathogen's growth is approximately 22°C to 28°C, which is ideal for both spore germination and hyphal colonization.

Orchards with high planting density and poor airflow are particularly vulnerable, as the high humidity within the dense canopy prevents foliage from drying.

Prolonged leaf wetness duration is the critical trigger for infection, especially during the vulnerable stages of flowering and fruit set.

Stress factors such as poor soil nutrient management or previous insect damage provide entry points for the pathogen to establish itself more effectively.

Anthracnose causes direct economic loss by reducing fruit yield and lowering the market quality of harvested feijoa fruits, rendering them unsellable.

The loss of foliage reduces the tree's photosynthetic capacity, which impacts overall growth, future bloom potential, and the accumulation of energy reserves.

Chronic infections can lead to the systemic weakening of branches, resulting in reduced structural integrity and potential branch death over several years.

Infection cycles contribute to the buildup of inoculum in the orchard, increasing the severity of the disease in subsequent growing seasons if left unmanaged.

Increased expenditure on protective fungicides and additional labor for sanitization significantly elevates the cost of production for the orchard owner.

The primary control strategy involves strict field sanitation, which includes removing and destroying all infected fallen leaves, twigs, and fruit mummies.

Regular pruning is essential to maintain an open canopy structure, ensuring better airflow and allowing sunlight to penetrate, which inhibits fungal development.

Chemical control includes the application of copper-based fungicides or systemic anti-fungal treatments during the critical window before infection onset.

Balanced fertilization and good water management, specifically avoiding overhead irrigation, help maintain plant vigor and reduce the duration of leaf wetness.

• Monitoring orchards for early symptoms during warm, wet weather.
• Applying preventive fungicides before the peak rainy season.
• Promoting air circulation through systematic pruning practices.