Asparagus stem blight is a devastating disease that occurs in almost all areas of asparagus production. When the disease is light, the plants die sporadically and the yield is reduced. When the crop is destroyed, it is destroyed by the whole field and the harvest is almost eliminated, causing huge losses to the bamboo shooter. At present, it has entered a period of high temperature and high humidity, and it is also a period of high incidence of asparagus diseases. Especially in old planting areas, stem blight of asparagus has become the major disease that restricts production. The following describes the symptoms and prevention methods of stem blight of asparagus for reference.
First, the harm symptoms
Asparagus stem blight pathogens mainly infect the shoots and shoots of bamboo shoots. Asparagus sprouts and shoots are affected by stem blight pathogens and form lesions. Lesions can be chronically affected by environmental conditions. Type and acute type of lesions.
1. Chronic lesions. In the case of relatively dry air, the development of lesions is relatively slow, the lesions are relatively small, the edges of the lesions are relatively clear, and the hazards are also small. This lesion is called chronic lesions. If asparagus shoots or shoots are infected by pathogenic bacteria to form lesions, the edges of lesions are reddish-brown or brown, and the center is gray-brown. The lesions are oval or oblong, and a small number of black spots are formed on the lesions. Asparagus shoots on the ground suffer from stem blight pathogens to form chronic lesions, generally do not cause bamboo shoots to die. However, due to the robust development of bamboo shoots, the photosynthetic function of bamboo shoots decreased, and the transport and accumulation of fertilizers, water, photosynthetic products and other substances were affected, resulting in a decline in the yield and quality of asparagus.
2. Acute lesions. In the case of heavy rain or high humidity in the field, after the stems of Asparagus are infected with stem blight, the lesions spread more rapidly, the lesions are larger, the lesion edges are unclear, and the hazards are greater. This lesion is called Acute type lesions. The lesions can penetrate deep into the pith of the stems and branches, and the lesions are yellow-white or gray-white after the dehydration and dryness of the lesions. The tissues within the lesions are susceptible to ulceration. After stems and branches of asparagus were infected by stem blight bacteria to form acute lesions, although the lesions above the previous lesions had not died, the lesions had become loose and empty inside, and the stems and branches at the lesions were found. It is not hard to pinch when pressed tightly, and the interior is gray-brown and dry. Although some lesions did not invade the inside of stems and branches, the lesions circled the stems and branches for a week, and the stalks of asparagus were relatively fragile. Both of the above conditions are easy to break or fall down, causing the bamboo shoots to die. Asparagus stem blight is the most susceptible to diseases in the lower part of the stem, the most serious harm, followed by the middle and upper stems and branches, scales and mimicry can also be the disease, the disease can be covered with the disease quickly when the entire bamboo shoots quickly withered . Asparagus suffers severe crop damage caused by stem blight, resulting in a yellow crop in the field and severely reduced or lost asparagus. Therefore, the acute damage caused by stem blight of asparagus is the most serious economic loss.
Second, the incidence conditions
1. The variety is poorly resistant. The variety cultivated by asparagus is not a hybrid generation, and the disease resistance is reduced year by year. Once the environment is suitable, it will be widespread.
2. Environmental conditions conducive to disease. The temperature range for the growth of the bacteria is 16°C to 35°C and the appropriate temperature is 23°C to 26°C. The temperature in the spring is closely related to the onset of disease, especially in July, August and September. It is the vegetative growth stage of asparagus, which is also the peak period of bacterial infection. The rate of diseased plants basically increases with the increase in the number of rainfalls. Ten days after each rain, there will be an onset peak in the fields.
3. Diazo light phosphorus and potassium. Some bamboo farmers are pursuing the immediate interests and reapplying nitrogenous fertilizer or only nitrogenous fertilizer to make bamboo shoots grow densely. The stalk cell walls are tender and thin, and pathogens are easily invaded. According to the survey, the application of three elements of fertilizer field shoots, the incidence of strains only accounted for 10%, only the application of urea strain rate of 58%.
4. Clear Garden is not a net disease. Clear gardens are not timely, clear gardens or clear gardens are not thorough, resulting in a large number of pathogenic bacteria remaining in the field.
Third, prevention and control measures
1. Use resistant varieties. Asparagus varieties have great differences in resistance to stem blight, so choose high-quality, high-yield, disease-resistant F1 generation varieties, such as Apollo, Purple Passion, Atlas and so on.
2. Select the appropriate plot. It is necessary to choose sandy lands or loam soils with flat terrain, fertile soil, convenient irrigation and drainage, and good ventilation. It is important not to plant asparagus where the soil is heavy, the terrain is low, and the drainage is poor.
3. Clean the pastoral. In order to reduce the pathogens, it must be thoroughly and cleanly when clearing the garden. Sick branches, leaves, and debris should be completely removed from the shoots and burned or buried deeply. After the end of the clear garden, the soil was disinfected with 50% carbendazim 500 times.
4. Reasonable fertilization. Promote the application of formula fertilization, appropriate topdressing of potash fertilizer and phosphate fertilizer, control the use of nitrogen fertilizer, promote robust growth of plants, and increase disease resistance.
5. Strengthen field management. Especially after entering the rainy season, the water in the fields must be drained in time after the rain. Timely cultivator weeds, and timely removal of diseased stems, thin branches topping, the second year after planting, avoid interplanting other crops to prevent field closure, poor ventilation and light transmission, can reduce the incidence of the disease.
6. Chemical control. 50% of carbendazim 500-600 times solution, "Nongkang 120" 200 times solution, 40% of Scutellariae EC 800-1000 times solution can be used. It is sprayed once in 7-10 days at the beginning of onset. 5 to 7 days to spray 1, depending on the condition of the spray 3 times.
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