What are the symptoms, causes and characteristics of oleander witches 'broom disease? How to prevent?
The pathogen of oleander branch is mainly harmful to oleander branches, and the disease begins to occur on individual branches, showing a large number of axillary buds and adventitious buds sprouting, clustered with many thin branchlets, stagnant growth of main shoots, shortening of branchlets, smaller leaves and inconspicuous mosaic. The susceptible twigs can also extract twigs, the base of the newly drawn twigs is swollen, showing reddish, often clustered clusters, the branchlets are getting thinner and weaker, the leaves are getting smaller and smaller, the appearance is like a bird's nest, forming typical arbuscular symptoms. Most of the injured branchlets are erect and there are nodules in the branches. The cortical rot strips off and falls into ulcers, and finally the whole plant dies.
Oleander clump disease is caused by mycoplasma infection. This mycoplasma is polymorphic, with a round or oval diameter of about 53-700 nm, which infects and spreads the disease.
The mycoplasma of oleander arbuscular disease exists in the parenchyma cells of oleander phloem. Disease can be transmitted by cutting and grafting of diseased branches. The disease mostly occurs in more than five-year-old trees, and young trees aged 1-5 years generally do not suffer from the disease or suffer slightly. Some parks and road trees have an incidence of almost 100% and a mortality rate of more than 60%. The severity of the disease was related to the flower color of the varieties. Safflower oleander was the most susceptible, white oleander was less susceptible, and Huanghua oleander was resistant.
Prevention and cure method
The main results are as follows: 1. When cultivating seedlings, disease-free plants should be strictly selected as mother trees to collect cuttings, and tetracycline 1000-2000PPM (1/1000000) should be soaked in tetracycline for 2-4 hours before cutting. It is forbidden to transport cuttings and seedlings from the disease-free area to the disease-free area.
2. The lightly diseased branches in the early stage of the disease should be sawed off as soon as possible, and the seriously diseased plants should be dug up and burned centrally.
3. Do not plant oleander with a single flower color, but use a variety of flowers and colors as far as possible to reduce the further spread of the disease.
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Propagation management of oleander
The propagation method of oleander can be propagated by cutting, ramet and striping, among which cutting is the most commonly used propagation method. Cutting can be carried out in both spring and summer. If the cuttings were soaked in clean water for 7 ~ 10 days before cutting and kept fresh, they could take root ahead of time and the survival rate would be improved. The specific method is that the 1-to 2-year-old branches cut in spring are cut into stem segments of 15 cm ~ 20 cm, 20 or so are tied up in a bundle, soaked in clean water, and the water depth is 1 ℃ 3 of that of the stem segment. The water at the same temperature is changed once every 2 days, and the temperature is controlled at 20 cm ~
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Cutting technique of oleander in spring
Oleander has long leaves like bamboo, flowers like peaches, and a long flowering period, which can last from mid-April to mid-September. Blooming flowers, thick green branches and leaves, proud frost fighting snow in winter, has a high ornamental value, is an excellent green tree species. At the same time, it has strong resistance to sulfur dioxide, so it is also an ideal plant for factory greening. The propagation of oleander is relatively easy, and it can be propagated by means of pressing, tillering, cutting and so on. The number of female plants is limited by striping and tillering, so it is not easy to propagate in large quantities. Use spring field cuttings
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