What is Alternaria?

Alternaria is a genus of fungi with at least 50 species. It is quite ubiquitous in the environment, and is one of the fungi that humans interact with most frequently, on a variety of levels. Alternaria species are one of the main causes of crop blight, and also cause allergies and infections in some people and animals. Mycologists, people who specialize in the study of fungi, estimate that hundreds of species will eventually be identified in this genus, with more being added to the list of known species all the time.

These fungi are asexual, they reproduce by budding and create club-shaped spores that join in chains to facilitate the spread of the fungus. Alternaria species are generally gray to black in color, and their colonies have a soft to woolly texture. When disturbed, a colony can break apart, spreading the fungus through the air in a black cloud. This is a common problem for farmers facing crop infestations, as removal of the infected crop inevitably releases spores of the fungus into the air, contributing to its spread. Mushroom cloud can also contribute to the development of respiratory problems.

In the natural environment, Alternaria can be found anywhere there is cellulose, as these fungi feed on cellulose. This includes decaying plant material and live cultures. The fungus also grows in homes and can be spread through waterways. Alternaria is a very hardy fungal species, remaining dormant during prolonged dry periods and quickly re-emerging as soon as a water source becomes available again. The colonies also grow very quickly, allowing the fungus to take over an area very quickly.

For farmers and gardeners, Alternaria is a concern because it can cause plant blight. When it settles on the plant, it classically causes a ring of dead tissue to emerge, and this ring slowly widens and eventually kills the plant or creates a series of unsightly spots. Controlling Alternaria can be difficult because it spreads so easily, and an estimated 20% of crop damage worldwide is caused by these busy fungi.

For animals, Alternaria can cause respiratory infections and allergies, especially if they are exposed for an extended period of time. Fungi in this genus appear to contribute to the development of asthma in children and can cause coughs and respiratory infections. In people with compromised immune systems, fungi can also cause more serious infections of the skin, mucous membranes, and internal organs.

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