Introduction About cotton Cotton diasesis

COTTON DISEASES CAUSED BY FUNGI AND MEASURES TO COMBAT THEM
Plan:

1. 
   Introduction
   
2. 
   About cotton
   
3. 
   Cotton diasesis
   
4. 
   Cotton root
   

Intoduction
Cotton is the collective name given to four species of plants in the genus Gossypium, Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum and Gossypium herbaceum which are perennial shrubs in the family Malvaceae grown for the fluffy fiber which protects the seeds of the plant. G. hirsutum accounts for approximately 90% of world wide cotton production today. Cotton plants possess a main stem giving rise to several branches at the top. The leaves of the plant are spirally arranged on the branches, have long petioles and have 3–5 triangular lobes. The plant produces a single flower on each axillary branch which can be red-purple, yellow or white in color and forms a leathery, oval seed capsule, or 'boll' which is 2–6 cm (0.8–2.4 in) long. Mature bolls will usually split open to reveal the characteristic white cotton fibers and the seed. The cotton plant can reach heights of 1–1.5 m (3.3–4.9 ft) and is usually cultivated as an annual, surviving only one growing season. Cotton may also be referred to as tree cotton and its center of origin is unknown although the plant has diversified from Mexico, north-east Africa and Arabia and Australia.

About cotton
Gossypium hirsutum
Ascochyta or Wet Weather Blight – (fungus – Ascochyta gossypii): The disease is prevalent in most cotton producing areas of the state. Both seedlings and older plants are susceptible, but younger cotton is more seriously injured. An entire stand may be lost as a result of the fungus attacking the hypocotyl and killing the plant. Serious outbreaks of the disease may follow extended rainy periods with serious defoliation occurring. The damage is generally spotty and many plants recover when dry, warmer weather returns. The disease occurs on the leaves, stems and branches. First, small, round, reddish-brown spots with a dark brown border appear on the leaves. Later, the center of the lesions become ashy in color and may fall out. The lesions often occur at the base of the petiole. Defoliation may result from large lesions that coalesce. On stalks and branches, the lesions are dark brown, elongated and slightly sunken cankers. Under conditions favorable for the disease, the lesions may completely encircle the stem or branch and kill the plant above the lesions. The fungus may be seed-borne but it primarily survives in the soil on the infected plant residue. Use of acid delinted seed and suitable seed treatment fungicides will minimize carry-over. Plowing under plant residues and crop rotation also aid in reduction of the disease.