In recent years, with the promotion and application of new maize varieties, corn rust is a common disease on corn. The occurrence of a wide range, all have different degrees of damage, so that corn plants dry, the grain is not full, resulting in reduced production. The lighter ones cut production by about 20%, and the heavy ones by 30%.
I. Symptoms Corn rust mainly invades corn leaves and occasionally damages the corn stalks and leaf sheaths. At the onset of the disease, at the base of the leaf blade and on the upper main vein and on both sides, light yellow spots were scattered or aggregated, and after the protrusions formed reddish-brown freckle, ie, the pathogenic summer spores heap. Late lesions form black freckle, the pathogenic teliospores heap. When the corn rust occurs seriously, the leaves are covered with spore heaps, resulting in a large number of leaf dry, premature aging of plants, and incomplete grain, resulting in reduced production. When it is heavier, the leaves are broken from the victim's site, and the whole plant is dry and the production is reduced seriously.
Second, the incidence of law The occurrence of corn rust is caused by foreign bacteria. Seen in late May, the maize rust teliospore reached its peak in July and another peak appeared in mid-September. The uredia spores were seen at the end of June and peaked in mid-August. The infection period of maize rust was from mid-June to mid-July. Corn rust began in mid-July and the spores were transmitted by air currents and repeated infestation. The onset of disease was at the end of August. In the onset of the field, it begins to expand downward from the top of the plant.
Third, the incidence conditions
1. Climatic conditions High temperature is conducive to spore survival, germination, transmission, infection, and disease severity.
2. The soil and planting terrain are low, the planting density is high, ventilation and ventilation are poor, and the incidence is serious.
(1) Disease resistance varies greatly among varieties. For example, the onset of serious diseases on the 2nd, 4th, 12th, 13th, and Xiyu 3rd, etc.
(2) The leaf color of the varieties and the number of leaf hairs are related to the severity of the disease. Leaf color yellow and less leafy varieties usually weigh heavily.
3. The occurrence of fertilization disease has a great relationship with fertilization in the field. Sites with partial or multi-fertilizer application have a heavy onset.
Fourth, control methods
1. It is an economical and effective measure to plant varieties that are resistant to maize rust. Application of disease-resistant inbred lines to prepare new varieties and use existing disease-resistant varieties, such as Nongda 108, Ludan 50, Jingza 6, Zhongdan 2.
2. Rational fertilization using formula fertilization, application of phosphate fertilizer, potash fertilizer, to avoid partial nitrogen fertilizer, in order to improve plant disease resistance.
3. Cultivation measures appropriate early sowing, reasonable dense planting, cultivating loose soil, pouring the right amount of water, create an environment conducive to crop growth and development, improve plant disease resistance, reduce the incidence of disease.
4. Chemical control The role of chemical agents is to inhibit spore germination and prevent disease.
(1) The application of spores during the peak period has an inhibitory effect on spore germination. 97% of the enemy diner drug 250 to 300 times, 50% of the special WP wet spray 800 times spray.
(2) In the early stage of the onset of corn rust, medication is used for prevention and treatment. 0.2 Baume degrees lime sulfur, 25% triadimefon 1000 to 1500 times, 12.5% ​​speed Poly WP 3000 times, 50% carbendazim 500 to 1000 times, 20% rust Emulsion 400 times liquid, 97% diene natto 250 times liquid spray, 30% Teflon wettable powder 2000 times, 40% Fuxing emulsion 9000 times, 50% colloidal sulfur 200 times.
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