Matters needing attention in soilless cultivation of flowers, occurrence and control of root cancer of flower seedlings

Root cancer disease, also known as root cancer disease, is one of the most common root diseases in garden flower seedlings. according to statistics, root cancer hosts up to 60 families and more than 300 species of plants. Such as cherry blossoms, peaches, roses, roses, ginkgo, carnation, dahlias, begonia, plum blossoms, cloves, geraniums and other flowers and trees, as well as grapes, plums, apricots, pears, apples, kiwifruit and other fruit trees all occur, which is a thorny problem in prevention and control.

Harmful symptoms. It mainly harms the root neck, main root and lateral root, while the seedlings mostly occur in the place where the scion and rootstock heal. At the beginning of the disease, there were small round tumors, and then gradually enlarged, hardened, rough surface, cracked, color changed from light to dark brown or dark brown, and Lignification inside the tumor. Tumors vary in size, as big as fists or larger, and the number varies from several to a dozen. Due to the destruction of the root system, the diseased plants of flowers and trees grow slowly, and the serious ones die of the whole plant. The disease is very stubborn. Even if the cancer is removed, it can often grow again.

The regularity of the disease. The pathogenic bacteria overwintered in the cortex of the tumor tissue, or when the tumor tissue rotted and ruptured, the bacteria mixed into the soil, and the cancer bacteria in the soil could survive for more than one year. Germs are transmitted by water flow, underground pests, grafting tools, farm tools, etc., and diseased flowers and trees can be transported and transported over a long distance. Pathogens invade the host through wounds, insect injuries, mechanical injuries caused by farming, cuttings, marriage interfaces, and other injuries, all of which can be the ways for bacteria to invade. The occurrence of the disease is closely related to soil temperature and humidity, which is beneficial to bacterial infection and disease, and the soil temperature of 22 ℃ is the most suitable for the formation of cancer, and the soil temperature of more than 30 ℃ can hardly form tumor. Soil and pH are also related to the disease, alkaline soil is conducive to the occurrence of root cancer, while acidified soil disease is less, the soil with heavy clay, low-lying terrain and poor drainage is more serious, and the disease of flowers and trees in continuous cropping cultivation is serious. In addition, the disease is more serious in the nursery of flowers and trees with extensive tillage management, many underground pests and soil nematodes, and many kinds of mechanical damage. If the wound does not heal well when the cuttings are pseudo-planted, the nursery seedlings are also prone to disease.

Prevention and control methods. The first is to strengthen quarantine. Discarded diseased plants or foreign seedlings should be abandoned and suspicious seedlings can be found. Soak in 500-2000PPM streptomycin solution for 30 minutes, or soak in 1% copper sulfate solution for 5 minutes, or 2% lime water for 1-2 minutes. Plant after rinsing with clean water. When seedlings are built and planted, the introduction of seedlings or cuttings from the disease area should be avoided, and when diseased seedlings are found, they should be completely removed and burned. The second is to strengthen cultivation management. Planting after rotation or disinfection of soil with chloropicrin for more than 2 years in seriously ill areas. In neutral or slightly alkaline soil which is suitable for the occurrence of root cancer, more organic fertilizer should be applied to improve soil acidity and soil structure, and the root or stem base of flowers and trees should be hurt as little as possible when ploughing and weeding. Pay attention to timely control of underground pests and soil nematodes to reduce insect damage; pay attention to the elimination of stagnant water after rain, reduce soil moisture, promote the growth of flowers and trees and improve disease resistance. The third is to scrape off the diseased tumor or remove the diseased plant. After finding that the nursery or planted flowers and trees are infected with germs, you should remove the surrounding soil in time, remove the tumor thoroughly with a scraper until the disease-free xylem is exposed, and protect the wound with a high concentration of stone-sulfur mixture or Bordeaux solution to avoid reinfection. The seriously diseased plants that can not be treated should be cleared in time, the residual roots should be cleaned up thoroughly, and centralized burning should be done. For mildly diseased plants, the roots can be irrigated with 300,400 times of antimicrobial agent, or the wound can be smeared with 500-2000PPM streptomycin or 500-1000PPM oxytetracycline, or 5% ferrous sulfate. It is also reported that the application of methyl ice iodine solution (50 parts of methanol, 25 parts of glacial acetic acid, 12 parts of iodine tablets) has therapeutic effect. Agrobacterium tumefaciens 84 can also be released for biological control. Fourth, grafting should avoid wound contact with soil, and grafting tools can be sterilized with 75% alcohol or 1% formaldehyde solution.