Anthracnose

The fungus survives primarily in infected plant debris, soil, and on seeds. It can persist in the field for several seasons if the environmental conditions remain favorable.

The biological cycle involves the production of small, cushion-like structures known as acervuli, which erupt through the epidermis of the plant tissues to release masses of spores.

These spores, or conidia, are dispersed by wind, splashing rain, and physical contact, allowing the fungus to infect new leaves, stems, and fruits throughout the growing season.

The fungus penetrates plant cells and secretes enzymes that decompose host tissue, leading to the characteristic dark lesions and necrosis associated with the disease.

The initial symptoms usually appear as small, circular or irregular spots on leaves. These spots are typically dark brown, black, or reddish with a distinct border.

Under humid conditions, the centers of these lesions develop small, pinkish, or orange gelatinous spore masses, which are a hallmark of the Colletotrichum infection.

On stems and branches, the infection often causes elongated, sunken lesions known as cankers. These cankers can girdle the stem, leading to the collapse of the upper plant parts.

Fruit symptoms involve water-soaked lesions that enlarge rapidly, turning into deep, soft rots. Infected fruits often become covered in slimy spore masses.

• Dark necrotic lesions on foliage.
• Sunken cankers on stems and petioles.
• Pink or orange slimy spore structures.
• Premature defoliation and fruit decay.

Anthracnose development is heavily dependent on high moisture levels. Frequent rains, high relative humidity, and heavy dew are perfect for spore germination.

The disease thrives in warm temperatures, typically between 20°C and 28°C (68°F–82°F). Rapid disease spread is common during warm and wet summer periods.

Spores are easily spread across fields through water splashes, wind currents, and mechanical tools used during harvesting or pruning operations.

Poor ventilation in greenhouses or high-density planting in fields creates a humid microclimate, which is highly favorable for rapid pathogen colonization.

Stress factors such as nutrient deficiencies, pest damage, or improper pruning make plants significantly more susceptible to successful infection by the fungus.

Anthracnose causes massive economic damage by destroying harvestable fruit and reducing plant vigor, leading to significant yield losses in commercial production.

Leaf infection severely impairs photosynthetic capacity, causing stunted growth and poor fruit quality, which renders the produce unmarketable in many cases.

Infected seeds often show low germination rates, and the resulting seedlings may suffer from pre-emergence or post-emergence damping-off, weakening the crop stand.

Severe infections can lead to total crop failure if management interventions are not implemented early in the growth stage of the plants.

The disease also affects post-harvest quality, as hidden infections can cause fruits to rot rapidly while in storage or during transportation to the market.

The primary control strategy involves using certified, disease-free seeds and planting resistant or tolerant cultivars where available in the market.

Sanitation practices are essential, including the removal and destruction of infected plant material and deep plowing to bury crop residues post-harvest.

Fungicide applications, both systemic and contact, are effective when applied preventively or at the very first signs of infection to stop the disease cycle.

Optimizing irrigation systems to avoid overhead watering and ensuring proper spacing between plants helps maintain a drier canopy, reducing disease pressure.

Regular crop scouting is vital to detect the disease early, allowing for targeted chemical treatments and preventing the pathogen from reaching epidemic levels.