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Host and Symptoms
Alternaria Alternata is a fungus that causes leaf spotting to over 300 species of plants as well as potential health risks to humans. Not only this, but Alternaria Alternata can cause leaf blight, cankers, sores, and rots to several hundred species of plants. Alternata blight is the blight caused by the alternata genus and contains disease-causing microorganisms similar to early blight. The symptoms of Alternata blight develop from the leaf tips and usually spread to stem, root, etc. If the species is severely infected, the fungus can create large lesions on the plant. The host of Alternata blight are usually tomatoes and potatoes. A widely recognized symptom caused by this pathogen includes small, dark lesions of dead cells on leaves. The symptoms of Alternata blight and early blight are often times confused, but Alternata blight contains brown spots with rings, and overall less lesions when compared to early blight. The leaves that are in the middle of the host plant are most susceptible to disease from Alternata blight and present the highest incidence rate.

Environment
The destruction of plants due to Alternata blight usually occur in humid, moist areas with adequate rainfall. Because the spread of this fungus is through their spores, the wind and rainfall commonly disperse the spores to other plants and infect them. Spores can travel through the soil and may even live within the soil. Because of this, they may infect tubers late within the growing season or during harvest. When spores reach susceptible plants, fungus grows and infects the plants. The lesions caused by this fungus were usually oval-like, dark, and brown and start on the lower leaves before spreading. The lesions spread through the entire leaf, causing it to darken and eventually die. The holes within the tubers caused by these infecting spores are called black pit.

Importance
Alternata blight is an important fungus to learn about because it has many detrimental and adverse effects to potatoes and tomatoes which are important crops and heavily incorporated vegetables in the human diet. Blight was responsible for the Irish famine of the 19th century because men depended on potatoes for the majority of their calories. The fungus contributes to a substantial amount of crop loss (mainly fruits and vegetables due to necrosis), which would reduce famine and malnutrition in underdeveloped, humid regions which may not have fungicides. Research has shown that the fungus can cause yield loss from almost 20-30%. Alternata blight is a serious economic issue as well because of the world's dependence on potatoes and tomatoes. Because of this dependence, fungicides need to be applied every 3-5 days which is costly. Studies have shown the United States alone spends about $80 million yearly on fungicides. There have been histories of epidemics caused by blight and the cost of managing blight can get upwards of $30 million.