These are fungi imperfecti which belong to artificial class of fungi. The presence of sexual stage of reproduction is controversial. There are more than 15000 species of imperfect fungi. They are septate and are unicellular. They resemble to yeast with respect to its cellular structure. Unlike basidiomycetes they have no clamp connection. Asexual reproduction occurs by formation of conidia. It includes red rot, early blight, helminthosporium, tikka disease and wilts. Red rot is caused by colletotrichum falcatum. It affects the sugarcane reduces juice content and bring about falling of leaves. Helminthosporium affects rice and causes brown life spot of rice. Bengal famine occurred due to helminthosporium. Early Blight occurs in potato and tomato and is caused by Alternaria solani. The leaves form brown spots with concentric rings. They have combination of longitudinal and transverse septa. Tikka disease is caused by crecospora which forms brown or black leaf spots. Conidia are filamentous in shape and have septa. Wilts occur due to blockage of trachery elements by fungal growth.