Occurrence and Control Techniques of Corn Leaf Blotch Disease

Chinese name: Corn blotch English name: Corn northern leaf blight Latin name: Helminthosporium turcicum Pass. Damaged crops: corn damage symptoms: corn leaf spot mainly damage, in severe cases also damage leaf sheath and temporal lobe. The disease begins with the lower leaves of the plant and expands upward. The lesions are long spindle-shaped, grayish-brown or yellow-brown, 5 to 10 cm in length, and 1 cm in width. Some lesions are larger, or several lesions are connected to form a large, irregular, spotted lesion. Rainy and wet weather, dense gray mold layer can be densely stained. In addition, there is a lesion that occurs on disease-resistant varieties, spreading along the veins, showing a brown necrotic streak, surrounded by yellow or light brown chlorotic circles, with no spores or very few spores. The morphological characteristics of the pathogen: The gray mold layer produced on the lesion is the conidiophore and conidia of the pathogen. If the mold layer on the lesion is not obvious, moisturizing can be used to promote sporulation. The method is: spread the wet filter paper on the glass culture dish, cut the leaf segments with fresh lesions flat on the filter paper, and then cover the petri dish tightly. After 1~2 days, the mold layer on the lesion can be seen. . Conidiophores solitary or several bunched, unbranched, bluish-brown, conidiogenous on spore pedicel tip, pale bluish, fusiform or long spindle, erect or slightly curved to one side, with multiple divisions The umbilical spot clearly stands out from the distribution area outside the basal cell: The characteristics of the corn producing area in the country: The mycelium and the attached conidia in the diseased leaf tissue in the field surface and in the corn stalk can be overwintered and become the second year. The initial infection source of the disease. The mycelium buried on the diseased leaf 10 cm deep in the ground all died after winter. During the growing season of corn, the wintery fungus produces spores, which spreads to the leaves of the corn with the splash of rain or airflow, and is suitable for germination and invasion under conditions of temperature and humidity. Infected varieties, the bacteria quickly expanded after invading, about 14 days or so, you can cause local wilting, tissue necrosis, and then form dead spots. In moist climate conditions, a large number of conidia can be produced on the lesions, which spreads with the air flow and re-infects them several times, causing disease epidemics. The field has seen lesions: in northern China, spring maize in early June and summer maize in mid-July. Due to the coincidence of climatic conditions with the silking filling stage during the disease stage of the corn, the condition of the summer corn develops quickly and the victim is heavy. Disease conditions (1) Variety disease resistance is an important factor affecting the epidemic of large patch. In the 1970s, due to the large-scale planting of susceptible corn hybrids, widespread pandemic disease was caused in some areas and the losses were serious. (2) Due to the large amount of bacteria in wintering, the initial infestation occurs early and often in maize squatting grounds and near villages. (3) Climatic conditions are also important factors in the occurrence of disease. Temperatures of 20-25°C and relative humidity of 90% are favorable for spore formation, germination, and infection. Therefore, moderate-temperature and high-humidity climate conditions are conducive to the spread of large-spot disease. In the northern corn-producing areas, the rainfall from June to July exceeded 80 millimeters, and the rainy days were relatively high. Combined with the moderate rainfall in August, the condition was seriously developed. Control methods: selection of anti-resistant varieties, intensify cultivation and management, re-application of pesticides and other comprehensive measures. 1. Selection of resistant varieties and maize hybrids resistant to spot disease. 2. Implement rotation system to prevent corn cropping, deep-fall soil in autumn, deep-fall diseased plants, eliminate sterilization source, use corn straw as fuel, treat it as soon as possible after spring, and treat corn borer; Compost should be fully decomposed and straw fertilizer should not be applied in corn fields. 3. Improve cultivation techniques and enhance corn disease resistance. Early sowing of summer maize can reduce the incidence; Intercropping with wheat, flowers, raw sweet potato, and wide and narrow row planting; Reasonable irrigation, pay attention to field drainage. 4. Spraying control Before and after corn picking, the disease rate in the field reached more than 70%. When the diseased leaf rate was 20%, spraying was started. Anti-effective agents are: 50% carbendazim WP, 50% amifenzin WP, 90% mancozeb, all 500 times more water, or 40% EKS 800 times spray. The use of liquid medicine per acre of 50 to 75 kilograms, spraying every 7 to 10 days, a total of 2 to 3 times control. Commonly used agents: carbendazim enutropha

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