Introduction About cotton Cotton diasesis

Cotton Root Rot (fungus – Phymatotrichum omnivorum): Root rot appears suddenly, starting in early summer. It causes rapid wilting, followed by death of the plants within a few days (Figure 3). Usually, the leaves of the plant are not shed, but remain attached. The disease kills plants in circular areas ranging from a few square yards to an acre or more in size. The root system of affected plants decay. Scraping the taproot reveals a darkened, reddish to wine-colored stain. If examined soon after death, the stems will be near normal color internally. Vascular streaking is not present as in the wilt disease. Fine, light brown strands of fungal threads (rhizomorphs) are usually found on the roots. Under moist conditions spore mats may appear on the soil surface near diseased plants. These are 2-12 inches in diameter, first snow-white and cottony, later tan and powdery. Controls include management and cultural practices as no chemical treatment has been found that economically controls cotton root rot. Deep plowing approximately 12 inches with mold board plow, planting early maturing varieties to escape disease, addition of organic matter or green manure and crop rotation have proven to be the most effective control methods. To achieve maximum control, an integrated program involving all practices is recommended.
Root Knot (nematode – Meloidogyne incognita acrita): The symptoms caused by root knot vary from slight plant stunting to death in areas of severe infestation. Skippy stands, particularly in distinct areas of a field, are characteristic. In skip-row cotton, where current rows are laid out perpendicular to the previous year’s row, stunted cotton outlining the old rows may be noticed. Root knots are small and should be checked on plants dug with a shovel and not those pulled by hand, since pulling plants often results in just the tap root being extracted. Control root knot nematodes by: rotation with sorghum or small grains, and use of in-furrow nematacides.
Nematodes Other Than Root Knot (nematodes – lesion: Pratylenchus sp., spiral: Helicotylenchus sp., lance: Hoplolaimus sp., sting: Benlonolaimus sp., stunt: Tylenchorhynchus sp., reniform: Rotylenchus reniformis): Of these nematodes, reniform is the most important in cotton production in Texas. It has been found in very small numbers in three counties in the High Plains, but it is most prevalent in the Rio Grande Valley area.