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.
