Symptoms occur in all cotton districts. The main damage is cotton bolls. At the beginning of the boll, cracks, wormholes, cuts, or tears are generated at the boiled, yellowish-brown spots, followed by yellow-green or yellow-brown powder, filling the bell joints, causing the bolls to fail to crack properly, even when the rain or humidity is high, Growing yellow-brown or yellow-green villous mold, that is, conidial stems and conidia of pathogens, the quality of cotton wool is polluted to varying degrees or dry rot deteriorates.
Pathogen Aspergillus flavus Link called Aspergillus flavus, Aspergillus fumigatus Fres. Aspergillus niger van Tiegh. Aspergillus niger, all belong to the semi-mycotic fungus. Aspergillus flavus conidium subglobose, 1-2 layers of upper terrestrial stems, conidial stems saccate globose, conidium rough, round yellow, size 3.5-5μm, colony color is yellow at first, then turn yellow green To brown green. The Aspergillus niger conidiophores are cylindrical in shape and have a diameter of 40 μm. The conidiophores are smooth, greenish, and 2-8 μm in diameter. The conidia are spherical, rough and 2.5-3 μm in size. Aspergillus conidia ear gray black to black, round, radial, size 0.3-1mm; conidial stalk size 20-407-10 (μm); top capsular to nearly spherical, superficial two-stem; The spores are spherical, smooth at the beginning, and later become rough or raw. The colored material is deposited in a ring or nodule with a size of 2.4-4 μm, sometimes producing sclerotia.
Transmission routes and pathogenic conditions The bacteria survived in the Arctic Ocean with mycelia in the soil. In late spring, conidia are produced by airflow, directly from the wound or penetrating the epidermis. Aspergillus-infested cotton bolls can invade the seeds, causing seeds to carry bacteria, and become an important primary infestation source of the disease. The spores of the rot grown on the cotton bolls spread by wind and rain, and continue to infect the bolls with wounds and rips, and the diseases are continuously expanded. Contaminated seeds and diseased bodies in the year provided germs for the occurrence of disease in the following year, resulting in circulating infection. The disease is a high-temperature disease. It is a secondary disease of rotten bell. The growth of Aspergillus was 33°C. Shanghai Aspergillus fumigatus enters the stage of damage from more to mid-August to early September, and the incidence of disease is heavy in high-temperature years.
Control methods (1) Strengthen management of cotton fields, pay attention to proper close planting, and achieve good ventilation; adopt formula fertilization techniques and apply organic manure reasonably, the ratio of NPK is generally 1:0.4:0.8, and single application of nitrogen fertilizer is avoided; reasonable Irrigation, flood irrigation is prohibited, timely drainage after the rain, to prevent moisture retention. Pruning should be timely, clearing up dead leaves or rotten bells in the cotton fields, focusing on deep drought or burning, and reducing the source of bacteria. (2) Prevent and treat late-stage pests such as cotton bollworm, cornfield corn borer, and diamond drill in time to reduce wounds. (3) The diseased bell was found to be removed in time, the bell was quickly dried or dried, and the lint yield was increased. (4) Spray 50% benomyl WP 1500 times or 50% acetaminophen WP 2000 times, 70% WP WP 400-500 times, 36% methyl sulfide Feroxsilon suspension 600 times.
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