Anthracnose (Colletotrichum magnisporum)

The first symptoms of the infection appear as small brown or dark brown spots. Over time, these spots enlarge, taking on a sunken shape, which is a characteristic feature of anthracnose infections.

On the surface of the necrotic tissues, one can often notice the appearance of small cushions — acervuli, which indicate the sporulation of the fungus. These structures are often visible to the naked eye under sufficient lighting.

When stems are affected, cracking is often observed, which disrupts the normal sap flow within the plant. As a result, shoots or individual branches may quickly wilt and dry out.

The disease frequently affects reproductive organs. Flowers drop prematurely, and deep ulcers form on developing fruits, rendering them unsuitable for storage or market consumption.

• Darkening of tissues.
• Sunken necrotic spots.
• Visible sporulation growth.
• Premature wilting of plant parts.
• Deformation of fruits and shoots.

The causative agent of the disease is the fungus Colletotrichum magnisporum, which belongs to the genus of imperfect fungi (ascomycetes). It is a highly specialized pathogen that primarily infects tissues of above-ground plant organs.

The life cycle of the fungus includes the formation of conidial sporulation in the form of characteristic pustules called acervuli. Within these, spores (conidia) are formed, which serve as the primary source of infection for neighboring plants during the growing season.

The fungus survives in infected plant debris, soil, or on seed material in the form of mycelium or sclerotia. This allows the pathogen to withstand adverse conditions and initiate a new infection cycle as soon as warmer temperatures arrive.

The spread of the infection in the field occurs via wind, rain splashes, and insects that carry spores to healthy tissues. Active pathogen development requires direct contact with a moist leaf or stem surface.

The genetic variability of the species allows the pathogen to adapt to various environmental conditions, which complicates the breeding of crop varieties with absolute resistance to this disease.

Disease development is closely linked to high humidity, which is the key factor for spore germination. Frequent rains and prolonged morning dews are considered ideal conditions for the spread.

The optimal temperature for aggressive pathogen proliferation ranges from +20 to +25 degrees Celsius. Under these conditions, the incubation period is shortened to just a few days.

Poor agricultural practices, such as excessive crop density, create a specific microclimate in the lower parts of the plant. High humidity and lack of air circulation facilitate the rapid spread of spores.

Weakened plants, suffering from nutrient deficiencies or mechanical damage, become entry points for the infection. The fungus penetrates more easily through micro-cracks in the cuticle.

Crop rotation and the presence of infection sources on neighboring fields play a significant role. Infected remnants of the previous season's harvest in the soil create a high infection pressure for young seedlings.

The damage caused by Colletotrichum magnisporum lies in a sharp decline in the photosynthetic activity of the leaves. The plant loses the ability to accumulate organic matter, which leads to stunted fruit development.

Infection of the stem's vascular system leads to metabolic disruptions, causing overall growth suppression. In cases of massive infestation, a significant portion of the harvest can be lost in a short time.

The commercial quality of the produce is significantly reduced. Spotting and ulcers on fruits trigger secondary infections, including rots, making long-term storage impossible.

Significant damage is also inflicted on the seed bank. Seeds harvested from diseased plants act as hidden carriers of the infection, ensuring the disease is transmitted to future seasons.

Economic losses include not only direct loss of profit but also additional expenses for fungicide treatments throughout the growing season.

A key method of control is strict adherence to crop rotation, returning the crop to the same field no sooner than 3–4 years. This interrupts the life cycle of the fungus by depriving it of its host.

It is important to perform deep plowing or removal of plant debris after harvesting, as these remnants serve as the main reservoir for the infection during the winter period.

Using only certified, treated seed material prevents the introduction of the infection into clean fields at the initial stage of vegetation.

During the growing season, the application of preventative and curative fungicides from the strobilurin or triazole groups is recommended. Spraying should be performed before the onset of mass symptoms.

Maintaining optimal plant spacing promotes good aeration within the crop canopy, which critically lowers humidity and slows down the development of the fungal mycelium.