Life Cycle of Colletotrichum

Colletotrichum species cause a disease called anthracnose. This disease affects a wide range of plants worldwide, including different types of fruits, vegetables, legumes and cereals. Anthracnose is characterized by lesions that appear on fruits, stalks and leaves. It has an economic impact because fruits and vegetables with lesions are physically disfigured and cannot be sold. Colletotrichum thrives in warm, wet conditions, and can spread to affect up to 80 percent of a crop.

A Colletotrichum lesion first appears as a soft, sunken area that is light brown in color. Later, the lesion becomes covered with concentric rings of small, pink spots . These pink spots are the fruiting bodies, called acervuli, that produce the spores that spread the disease. Black spikes, resembling short hairs, may be visible among the fruiting bodies. For the rest of its life cycle, Colletotrichum has no visible symptoms.

The acervuli on the lesions caused by Colletotrichum release spores called conidia, which are dispersed by wind. Conidia can also be spread by rain, which splashes them onto other plants. When a conidium lands on a plant it can infect, it penetrates the plant's skin. Once inside the plant, the Colletotrichum grows and spreads as a mycelium, the fiberous form of the fungus. The symptoms of a Colletotrichum infection appear when the mycelium breaks through the surface of the plant and produces acervuli.

Colletotrichum occasionally produces a special form called a hypha instead of a mycelium. The hypha is the sexual form of Colletotrichum. Two hyphae from different Colletotricum individuals fuse together and produce a spore through sexual reproduction. This spore is called an ascospore, and it can survive in the environment for a very long time. Sexual reproduction produces genetically diverse offspring, and this genetic diversity helps Colletotrichum survive under different conditions and environments.

The spread of Colletotrichum can be controlled through the application of fungicides and by preventative measures. Don't bring infected plants into a field. If the disease has affected a crop, don't plant anything in the infected field for two years. Remove plant debris that may be contaminated with Colletotrichum spores from the field. Keep tools clean, because Colletotrichum spores can be passed from plant to plant on farming equipment or by workers handling infected plants.