Introduction About cotton Cotton diasesis

Virus Diseases: Several virus diseases have been described on cotton but are only of minor importance in Texas
Boll Rots (fungi and bacteria – caused by many parasitic and saprophytic organisms including: Colletotrichum sp. and Xanthomonas sp.): Symptoms may vary depending on the organisms involved. Generally, the first symptoms of boll rot are small, round, water-soaked spots on the bolls which may enlarge and become sunken and dark in color. Eternal symptoms may be absent but complete destruction of seed and fiber will occur. Infected bolls may be reduced by avoiding practices that promote rank growth, keeping cotton free of weeds and grasses, and skip- row planting. Heavy insect injury increases boll rot incidence. Boll rot is a problem of South and Central Texas. It is rarely seen on the High Plains.
Minor Leaf Spots (fungi – Alternaria sp., Cercospora sp., Rhizoctonia sp., Stemphyllium sp.): Two or more leaf spots may occur at the same time. Symptoms are varied, but generally these organisms cause circular concentric lesions similar to a target spot . These foliar diseases tend to be more prevalent at crop maturity and during periods of high humidity. Preventive control measures are most effective and include seed treatment, good management practices, and destruction of plant residue after harvest. Some varieties are more susceptible to late season leaf spot fungi.
Seedling Disease Complex (fungi – Rhizoctonia solani, Fusarium sp., Pythium sp., Thielaviopsis basicola): Seedling disease is caused by a complex of soil fungi which may occur separately or in combinations. These fungi are Pythium, Fusarium, Rhizoctonia, and Thielaviopsis. Symptoms include decay of the seed before germination, decay of the seedling before emergence, girdling of the emerged seedling at or near the soil surface, and rotting of root tips. Any one of these fungi or several working together can produce these symptoms.
Several practices reduce losses to seedling disease. These include using rotation, quality seed, timely planting and the use of fungicides. Producers can expect increased disease control as they increase the number of control practices used.
Rotation is the first line of defense against seedling disease. Following cotton with cotton will increase populations of seedling disease fungi in the soil. Fields should be rotated out of cotton for at least two years. Sometimes, problem fields can be identified and rotated out of cotton for a longer period of time.
The second line of defense is seed quality. Quality seed will emerge from the soil more quickly and develop secondary roots faster, therefore being vulnerable to fungal infection for a shorter period of time. Seed should be tested using the Cool-Warm Vigor Index (CWVI). This test is available at the Texas Department of Agriculture Seed Laboratory in Lubbock. Earliest plantings which have the greatest potential for seedling disease infection should be planted with seed rated excellent or at least good on the Cool-Warm Vigor Index.
Timely planting is the third step in reducing seedling disease loss. Unusually warm weather early in the season often entices growers to plant earlier than they should. Even good quality seed should not be planted until the 10-day average soil temperature at the eight-inch depth is 65^o F.
The most underrated seedling disease control practice is the use of fungicides to protect the seed and seedling. Most are applied by the seed supplier. However, hopper box treatments are also available. The advantage of hopper box treatments is that the decision whether to use them can be made the day of planting. Hopper box treatments in recent years have not out-performed the better seed treatments in replicated tests. The highest level of input for seedling disease control involves in-furrow fungicides. Cost of in-furrows is generally higher, in the $10.00 per acre range, compared to approximately $2.00 per acre for two of the better seed treatments in combination. In-furrows also have not out-performed the better seed treatments in tests on the High Plains.
There are a large number of fungicides labeled as seed treatments for seedling disease control, but only a few of them are used to any great extend in West Texas. These include Captain, Vitavax, Vitavax-PCNB, Apron, Nu-Flow M, Demosan and Baytan. Using combination treatments of some of the new systemic fungicides will provide a higher level of disease control. Combinations of two or three systemic fungicides in which each material is effective on a different seedling disease fungus provides much better control than just Captain. These double fungicide seed treatments cost approximately $5.00 – $7.00 per bag. This will be a $2.00 – $5.00 per acre cost at the 20 lbs. per acre planting rate recommended for the South Plains.