Stalk blight is a devastating disease (some local farmers call it “è¸è 瘟â€), which seriously threatens the normal production of alfalfa. After the damage, the stems die. In severe cases, the stems are dead and lodging, and the bulbs are not formed in the lower part. The bulbs are small, the fruit is deformed, the quality is decreased, and the yield is sharply reduced.
1. The main symptoms of the disease are the sheath, stem, flower and other parts of the mites.
1 leaf sheath. In the early stage of the infestation, the base showed dark green irregular water-like lesions, which soon spread to the whole leaf sheath. The diseased part became grayish white after drying, and there were black dots with black dots or different lengths. Point, which is the conidia disk of the pathogen. When the conditions are appropriate, the germs spread rapidly to the leafy stems.
2 stems. After the illness, the water-stained oval, fusiform or amorphous black-green lesions are also formed at the beginning. In the later stage, small black spots or short black lines will appear on the lesions. When the humidity is high, the lesions will be shallow. Gray mold layer, the lesions become strips when the damage is serious. At this time, the diseased stem tissue will become very soft, the diseased part will be sunken, and the whole plant will die, which will easily cause the stem to fall.
3 flower devices. It occurs mostly in the scales or the neck of the ear, causing the flowers to be yellow and the gray part of the disease can be produced in the diseased part.
2, the characteristics of the disease is a fungal disease, with mycelium and conidia discs with the diseased plants left in the soil or on the bulbs overwintering. In April of the next year, when the climatic conditions are appropriate, it will be invaded from the stomata of the sputum or directly penetrate the epidermis, and it can spread by storm or irrigation water. The early planting of the cockroach is the initial onset in August, and the August-September period is the peak of the disease; the late planting cockroaches are initially affected from the end of August to September, especially in the case of continuous foggy weather after the White Dew Festival, which can spread in the hot sun. Onset. The lowest temperature of the disease is 5 ° C, the highest temperature is 32 ° C, and the suitable onset temperature is 23 ~ 29 ° C.
When the long-term temperature of the twins is between 17 and 29 °C, it is conducive to the onset of rain or heavy fog and heavy dew. Planting with bulbs of diseased plants or continuous planting in seriously ill fields often has early onset and serious onset. In addition, the planting is too dense, the seal is too early, resulting in poor ventilation and light transmission in the field; or the application of excessive nitrogen fertilizer in the early stage of growth, lack of phosphorus and potassium fertilizer, plant length and weakness will aggravate the condition. There is a certain difference in disease resistance between different varieties. Generally, Dahongpao has stronger disease resistance than Susong and Guiling Horseshoe.
3, prevention and control measures 1 selection of disease-resistant varieties. In the old ward, it is possible to plant more resistant varieties such as squash and Dahongpao according to local conditions, and pay attention to the selection of bulbs of disease-free bulbs or light diseased fields.
2 Implementation of rotation for more than 3 years. Especially in the old production areas, the implementation of crop rotation is the most cost-effective measure to prevent the disease. After planting 1 ,, rotating other crops within 3 years, such as white vegetables, lotus roots and other aquatic vegetables or dry vegetables, can effectively prevent the occurrence of the disease.
3 Strengthen field management. It is best to manage the irrigation and drainage separately to avoid string irrigation or flood irrigation; timely remove the diseased plants in the field and bring out the burnout in the field to prevent the spread of the disease; appropriate application of potassium fertilizer can effectively improve the disease resistance of alfalfa; Timely burned the diseased bodies in the field.
4 pre-treatment. Before seedling, the bulbs are first placed in 50% captan WP 500-700 times solution, or 50% carbendazim WP 500-800 times solution, or 70% thiophanate-methyl WP. Immerse in 800 to 1000 times of liquid for 18 to 24 hours, and then carry out seedlings. At the time of planting, the seedlings are placed in the above-mentioned medicament or soaked with a 50% ether ester suspension of 2000 to 3000 times, and then planted in the field for 3 to 5 hours.
5 chemical control. Before the seedlings are sealed, the spray is prevented with a spray of 5% to 4000 times of 50% of the ether ester suspension, and sprayed once more every 15 days. In the early stage of the disease, spray the medicine once every 5 days. After the disease is controlled, spray it once every 10 days. Each time, you can choose one of the following medicines: 40% triadimefon·carbendazim WP 800-1000 times , 50% polysulfide wettable powder 600 ~ 800 times liquid, 50% prochloraz WP 1000 ~ 1200 times liquid, 70% methyl thiophanate WP 800 ~ 1000 times liquid, 70% propyl zinc Wet powder 500 ~ 600 times liquid. It is worth noting that before the onset of heavy rain, it is necessary to spray drugs to prevent and cure. After the rain, it is necessary to replenish the spray in time, and focus on protecting the new stems from the pathogens; choose 2 to 3 kinds of agents to be used alternately, and the control effect is better.
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