Colletotrichum aotearoa

A typical sign of infection is the appearance of necrotic spots on leaves, fruits, and stems, which eventually turn brown or almost black. Concentric rings are often visible in the center of the affected areas.

In high humidity, pink or orange spore masses (conidia) form on the surface of the lesions. This is the most diagnostic sign confirming the presence of a fungal infection.

Fruit infection results in the formation of deep, sunken spots that expand rapidly, leading to tissue decay. Damaged fruit loses its marketability and becomes unsuitable for storage and transportation.

On young shoots, the infection causes deformation and tissue necrosis, leading to general plant weakness. In severe cases, premature leaf drop and fruit abortion are observed.

Systemic infection can lead to the wilting of individual branches or the entire plant due to the blockage of vascular tissues by the fungal mycelium and its metabolic byproducts.

Colletotrichum aotearoa is an ascomycete fungus belonging to the Colletotrichum gloeosporioides species complex. This pathogen is a causal agent of anthracnose, affecting a wide range of agricultural and ornamental crops.

Microscopically, the fungus is characterized by the presence of conidia formed in specific structures called acervuli. These structures facilitate the mass dispersal of spores during the growing season under favorable weather conditions.

Genetic studies confirm that this species is closely related to many pathogens of tropical and subtropical fruits. Identification of the species often requires molecular genetic analysis due to high morphological similarity with other members of the genus.

The pathogen is capable of surviving for long periods in plant debris and soil, making it highly resistant to adverse environmental factors. The ability to overwinter ensures the annual resumption of the infection cycle in fields.

In the life cycle of the fungus, both asexual reproduction and the potential for forming sexual structures play an important role, which contributes to the accumulation of genetic diversity and the emergence of more aggressive strains.

The development of the disease is directly dependent on high humidity and moderately warm temperatures. Prolonged periods of rain and heavy dew are critical factors that trigger epiphytotics.

The optimal temperature range for spore germination and plant tissue infection is between +20 and +28 degrees Celsius. At temperatures below +10, the development of the fungus slows down significantly.

Dense planting and lack of ventilation in greenhouses create an ideal microclimate for the rapid spread of spores from infected plants to healthy ones. Crowded crops prevent the leaf surface from drying quickly.

Mechanical damage to tissues caused by pests, hail, or careless handling significantly facilitates the penetration of mycelium into the plant. Open wounds become entry points for the infection.

The presence of free moisture on leaves for more than 6–8 consecutive hours is a sufficient condition for the successful invasion of the pathogen into the plant epidermis.

The primary damage is the reduction in crop yields due to fruit infection and the loss of photosynthetic leaf area. The pathogen is capable of destroying up to 50–70% of the harvest in years with favorable weather conditions.

Affected produce loses its quality characteristics, including taste and shelf life. Even minor infection at harvest leads to rapid development of post-harvest rots.

The infection weakens the plant's immune system, making it more susceptible to other pathogens and environmental stressors such as drought or nutrient deficiencies.

The need for additional fungicide applications results in a significant increase in production costs, which lowers the profitability of farming operations.

In agroecosystems, the spread of Colletotrichum aotearoa requires strict phytosanitary control, as the pathogen can affect a wide range of hosts, including weeds that serve as reservoirs of infection.

The protection system must be based on preventive measures, including the use of healthy planting material and crop rotation. It is unacceptable to plant susceptible crops in fields where disease outbreaks have previously occurred.

• Regular removal and destruction of plant debris, which are the main sources of inoculum.
• Preventive application of contact fungicides during periods favorable for fungal development.
• Optimization of planting density to improve aeration and reduce humidity in the canopy.
• Timely control of insect pests to minimize mechanical damage to tissues.
• Use of systemic fungicides upon the detection of the first signs of infection to stop the spread of the disease.

The choice of fungicides should be based on monitoring and the rotation of active ingredients to prevent the development of resistance in the fungal population to chemical agents.

Adhering to irrigation practices that avoid overhead watering in the evening helps significantly reduce the risk of infection in closed-ground conditions.