Control techniques of Maize Leaf spot and Leaf spot

Corn leaf spot and small leaf spot are mainly harmful to leaves, and sometimes infect leaf sheaths and bracts. Leaf spot can not only damage the above-mentioned parts, but also damage ears. In many areas, these two diseases are collectively referred to as "corn spot". 1, symptom identification: the typical symptom of corn leaf spot is that the small spot expands rapidly and grows into a prismatic spot, the serious one is as long as 10mur30cm, and sometimes several spots are linked together to form irregular spots. At first, the disease spot becomes bluish gray, and finally becomes brown dead spot. When the air is moist, the disease spot can grow black mildew, that is, the conidiophores and conidia of the pathogen. The symptom characteristic of corn leaf spot is that the disease spot is small, generally no more than 1 cm long, the width is only limited between two leaf veins, nearly elliptical shape, the color of the spot edge is dark, it is Auburn. In addition, the number of disease spots is generally more. The pathogens of maize leaf spot and leaf spot overwintered with conidia attached to the remnant of the diseased plant, or with mycelium latent in the diseased tissue. The spores germinated in the second year caused the first infection, and the susceptible plants produced a large number of conidia, which were transmitted by wind and rain to cause re-infection. 2. The factors affecting the disease: the germination and invasion of spores and the formation and spread of spores all need certain climatic conditions, in which temperature and humidity are the main. The optimum temperature for spore formation, germination and invasion of Alternaria oryzae was 20-25C0, and the optimum temperature was 20-32C0, which was slightly higher than that of Xanthomonas oryzae, so it was more serious in summer corn planting area and spring corn area. 3. Control methods: the prevalence of the disease is determined by three factors: first, planting susceptible varieties in a large area; second, there are a large number of bacteria; third, there are suitable environmental conditions for the disease. Therefore, the prevention and control of diseases should start from these three aspects. The main results are as follows: (1) selection of disease-resistant varieties: this is the fundamental way to control large and small leaf spot, and there are obvious differences in disease resistance among different varieties. (2) eliminating the source of overwintering bacteria and reducing the amount of bacteria in the initial stage of the disease: the amount of bacteria can be reduced by crop rotation. In addition, the diseased remains in the field should be thoroughly removed and turned deep in time after corn harvest, which is an important measure to reduce the source of primary infection. (3) Chemical control: 40% gram distemper powder or 70% mancozeb wettable powder 600 times liquid spray. Spot disease 50% carbendazim wettable powder 500 times liquid, or 70% methyl topiramate wettable powder 500 times liquid spray. Pesticide application should start at the initial stage of the disease, so that the development of the disease can be effectively controlled, and it is necessary to spray again every 7 days or so.