The corn brown spot disease pathogens overwinter in the land or diseased bodies by dormant spores (sacs). In the second year, the pathogens spread to the corn plants by airflow. When they meet suitable conditions, they germinate to produce a large number of zoospores, and the zoospores are on the surface of the leaves. It swims in the water droplets and forms an infested silk, which often invades the young tissue of the corn at the trumpet stage. In July and August, if the temperature is high, the humidity is high, and the rainy days are more, it is conducive to the onset. In the infertile soil, the leaves are yellow and the disease is serious. In the soil with high soil fertility, the corn is strong, the leaves are dark green, and the disease is light or not. Generally, it is easy to cause disease when the corn is 8-12 leaves, and the disease will not occur again after 12 leaves of corn. Waterproof Polyester Mat,Polyester Mat,Needle Punched Polyester Mat Non Woven Geotextile Co., Ltd. , http://www.nsgeotextile.com
At present, it has entered the rainy season, and some common diseases such as brown spot on summer corn begin to show signs. Symptoms occur in corn leaves, sheaths, and stalks, sometimes with small yellow to round spots on the leaves and male flowers outside the ears. First occurs at the tip of the top blade, with the most lesions at the junction of the leaf and the sheath, with lateral banding. Initially yellowish or reddish-brown spots, the lesions are round, elliptical to linear or fusiform, and the leaf tissue near the bulge is often red, and small lesions often come together. In severe cases, there are several or even all of the leaves. Covered with lesions, the lesions on the leaves are often white and transparent; large brown spots appear on the sheath and on the veins, and the epidermis ruptures at the end of the disease, and the leaf tissue is necrotic, emitting brown powder (spore of pathogens) The capsule is partially spalled, and the veins and vascular bundles remain as filamentous. Most of the lesions on the stem occur near the node and are often broken at the center of the infection.
Corn brown spot control method: Apply enough base fertilizer. Generally, the seedling fertilizer should be applied in the 4-5 leaf stage of maize, and the nitrogen, phosphorus and potassium compound fertilizer should be applied 10-15 kg/mu, pay attention to the combination of nitrogen, phosphorus and potassium fertilizer. Reasonable topdressing, timely watering, timely cultivating and weeding can promote the healthy growth of corn, enhance disease resistance, and eliminate host and reduce disease . The planting density is appropriate, do not increase the density arbitrarily, improve the permeability of the field, and vigorously promote the technology of dry sowing and formula fertilization. Dry sowing can make the corn seedlings exercise, and the roots are deep and strong. Formulated with fertilization, nitrogen, phosphorus and potassium fertilizers are added to make the corn develop robust and rapid, and enhance the disease resistance of the plants.
Chemical control: attention should be paid to early prevention. In the 4 to 5 leaf stage of corn, 25% of the powdery rusting WP 1500 times liquid leaf spray per acre can prevent the occurrence of corn brown spot, or 50% of the WP 1500 times solution, 12.5% Heguoli WP 1000 times solution, 50% carbendazim WP 500 times solution. In order to improve the control effect, potassium dihydrogen phosphate, urea, etc. may be added in the chemical solution, and the application of the quick-acting fertilizer may be combined to control the spread of the disease, and promote the robustness of the corn and improve the disease resistance of the corn. According to the current rainy climate characteristics, spray bactericide should be 2-3 times, 7 days apart, within 6 hours after spraying, the following rain should be sprayed after rain.