Anthracnose is a group of fungal diseases that affect leaves, stems, flowers, and fruit, caused primarily by Colletotrichum and, to a lesser extent, by other genera such as Gloeosporium and Coniothyrium . It thrives in warm, humid environments , can begin silently, and continue post-harvest , reducing quality and yield. The fungus survives in plant debris and seeds and is dispersed by rain, sprinkler irrigation, wind, tools, and insects.
What is anthracnose and why is it a concern?
More than a single disease, it is a complex pathogenic system with strains ranging from highly host-specific to broad-spectrum (for example, some strains of Colletotrichum gloeosporioides ), complicating crop rotation . It affects vegetables (tomatoes, peppers, cucurbits), fruit trees (avocados, mangoes, papayas, citrus), ornamentals, and other trees. Symptoms intensify during prolonged rainy seasons; they decrease during dry periods , but the pathogen can remain dormant. Factors that favor its development include warm to hot temperatures (approximately 20–30 °C) , prolonged leaf wetness , dense canopies , and soils with high pH . The economic impact can be significant; severe losses have been documented in susceptible crops if action is not taken promptly.
How it spreads: infection cycle and sources of inoculum
The cycle begins when spores land on susceptible tissue and there is sufficient moisture for germination. Infection can be primary (from infected seeds or the soil ) or secondary (from active lesions caused by water splash).
- Survival between campaigns: on crop debris, tools, and weed hosts; some species survive for several years.
- Dispersion: rain splashes or spray, short/medium distance wind, sucking insects and field work.
- Terms and conditions: high RH y poor ventilation in closed planting frames.
- Seeds: the pathogen can travel on the cover; the heat treatment in water (temperature/time specific to the crop) reduces the risk.
In pruning and grafting, fresh cuts are frequent entry points if they are not disinfected.
Symptoms and signs for accurate identification
- Sunken and dark lesions on leaves, stems and fruits; well-defined edges, sometimes with concentric rings.
- Leaf spots Gray-tan with brown/reddish/purple margins; may merge and cause premature defoliation.
- Stem lesions elongated and brown; if they surround the base, they cause wilting and bedridden.
- Damage to fruits: “bullseye” type lesions with appearance aqueous that deepen; frequent in tomato, papaya and cucurbits, before and after harvest.
- Black spots (acervuli) in advanced stages, where spores are produced.
- growth retardation due to less photosynthesis and nutrient absorption.
During dry periods, symptoms may subside, but the infection can reactivate with the return of moisture. For more information on identification techniques, review symptoms of pests and diseases in plants.
Comprehensive prevention and good practices
- Drainage and irrigation: avoid puddles; prioritize drip and water early so that the foliage dries before nightfall.
- Ventilation: space plants, tutored in tall species and pruning of low leaves in tomatoes and peppers to separate them from the ground.
- Hygiene: withdraw and destroy infected tissuesDo not compost cold. Alternatively, incorporate healthy waste into the soil or bury it deeply to accelerate its decomposition.
- Disinfection of tools: use solution bleach 1:4 water; avoid working with wet foliage.
Treatments: organic, biological and responsible chemical
- Cultural practices: remove affected leaves, shoots and fruits; apply padded to reduce soil splashing; improve nutrition with balanced fertilization.
- Organic control: preventive applications of horsetail extract y neem oil as a booster; respect doses and intervals.
- biocontrol: use of Trichoderma harzianum, Bacillus subtilis, B. amyloliquefaciens o Pseudomonas fluorescens in seed/soil/foliar to compete and antagonize the pathogen.
- Seed treatment: thermal in water (parameters according to culture) or biological to reduce initial systemic infections.
