Anthracnose of merremia

Colletotrichum merremiae is a specific fungal pathogen responsible for anthracnose disease in plants belonging to the Merremia genus. It is widely recognized in scientific literature for its potential as a biological control agent against Merremia peltata, a highly invasive vine that poses a threat to native ecosystems and agricultural lands in tropical regions.

As an ascomycete fungus, the pathogen infects the host tissue through localized penetration, leading to tissue necrosis. The biological cycle of this fungus involves the production of conidia within acervuli, which appear as small, dark pustules on the infected surface. These structures serve as the primary source of inoculum for the continuous spread of the disease.

Symptoms of the disease are characterized by irregular, dark brown or black lesions on the foliage. Under favorable environmental conditions, these spots expand rapidly, causing leaf chlorosis, premature defoliation, and stem dieback. The presence of a pinkish, gelatinous spore mass on the lesions is a definitive diagnostic feature of Colletotrichum species during high-humidity periods.

Optimal conditions for infection include high relative humidity and temperatures typically ranging between 22°C and 28°C. Rain splash is the most critical vector for spore dissemination, effectively moving the pathogen from infected litter to healthy canopy tissues. Furthermore, physical wounding of the plant due to herbivory or machinery significantly increases susceptibility.

Management strategies focus on reducing environmental conditions conducive to the pathogen's growth. In agricultural settings, this involves proper sanitation, which includes removing crop residues and debris where the fungus overwinters. In cases where the pathogen affects non-target species, broad-spectrum fungicides such as those containing copper or azoxystrobin may be applied.