In the process of tomato planting, it is often attacked by various diseases. Among them, it is necessary to control the seedling disease earlier and focus on it. Tomato seedling diseases mainly include rickets, blight, stem-based rot, and physiological roots. Prevention and treatment of tomato seedling diseases can not rely solely on chemical agents. It should be based on the selection of resistant varieties, pay attention to improving cultivation management measures, comprehensively prevent and cure various diseases, avoid the occurrence of physiological diseases, symptomatic medication, and appropriate medication. First, the main disease of tomato seedlings 1. Tripping disease The disease of the squatting is more than that in the early stage of the seedling bed. The young leaves of the seedlings are exhausted and the new roots are still not the most susceptible to the disease. The base of the diseased seedlings initially shows water-stained lesions, then browns and contractures, lodgings and death, when the humidity is high. Produces white flocculent hyphae. The continuous low temperature and high humidity of the seedbed are the main conditions for the occurrence of the disease. The rain is more or the irrigation is unreasonable, which will lead to the spread and reinfection of the bacteria. Poor light in the seedbed, poor ventilation and ventilation will also aggravate the disease. 2, blight The seedlings and seedlings that have just been unearthed can be harmed, especially in the middle and late stages. The base of the stem of the diseased seed becomes brown, and the diseased part shrinks finely, and the stems and leaves stagnate and die. A slightly larger diseased seedling or 5 to 10 days after planting, the dark brown oval lesions are produced at the base of the stem of the diseased seedlings, and the diseased plants are wilting during the day and recover at night. The lesions gradually sag and continue to expand. After 1 week around the stem, the base of the stem shrinks and becomes thinner. The stems and leaves of the shoots are wilting and dry, and do not fall, showing a dry shape. After colonization, the tissue rots when the humidity is high, and the diseased part produces a pale brown spider filamentous layer, and the sclerotia is formed later. The difference between squatting disease and blight Symptoms: The more prominent feature is that standing blight is standing and dying. The disease is that the seedlings fall and die. The blight began to produce elliptical irregular dark brown lesions. Later, the lesions expanded, and the stems were wound around the stem. The diseased part collapsed and the leaves eventually died. Symptoms: The blight seedlings are pulled up. When wet, the light brown spider silky mold can be seen, and the pathogen of the disease is white floc. Onset time: Tripping disease usually occurs in the early stage of seedlings, and the seedlings that have just been unearthed have more incidence; the blight disease occurs later, usually after the emergence of the seedlings after a period of growth. Incidence temperature: about 15 °C is easy to cause collapse. The suitable temperature for the onset of blight is 20 °C. 3. Stem-based rot After the onset of the seedlings, the base of the stem first becomes brown, and then the contraction of the diseased part becomes shrinkage, and the middle and upper stems and leaves gradually sag and sag. The diseased seedlings are wilting during the day and can be recovered at night. After a few days, when the lesions surround the stem for one week, the seedlings gradually die and do not fall. (root does not rot) 4, physiological roots Alfalfa roots are physiological diseases (non-invasive diseases) of tomato seedlings and are not caused by germs. The main causes of the disease are low temperature of the seedbed, excessive humidity, and insufficient light. Often, the tomato seedlings do not root, the roots become brown and rot, and the ground part is wilting. Strengthening the management of seedbed is an important measure to prevent and treat the disease. Tomato seedling diseases include Alternaria alternata, gray mold, early blight, late blight, root rot and so on. Most of them are diseased at the seedling stage, and occur in large areas at the later stage, which should be paid attention to when planting. Second, tomato seedling management points 1. Select and cultivate disease-resistant varieties according to local conditions According to the recommendation of the local agricultural technology center and the production experience over the years, different regions can choose the appropriate main disease-resistant varieties. 2. Strengthen seedbed management 1. Selected seedbeds. It is not conducive to the infection and spread of various pathogens by selecting plots with high terrain, which are not easy to accumulate water, ventilation, flatness and sunny. 2. The seedbed is best to use new bed soil. If the old bed soil is used, soil disinfection must be carried out to reduce the bacteria in the soil. For soil disinfection, carbendazim (control for gray mold), sclerotium (control for blight), fine nails of manganese and zinc (for the prevention of ovulation) can be used. 3. Control the field temperature and humidity. Pay attention to the ventilation and ventilation of the seedbed, which can reduce the humidity of the seedbed. Conditional heating of the bed soil can be heated by hot wire. It is also possible to apply grass ash on the field to adjust the acidity of the soil; on the other hand, it can reduce the soil moisture and maintain the soil temperature. Reasonable irrigation in the seedling stage, not flooding, string irrigation, over-watering. 4. Keep the garden sanitary and remove the weeds and susceptible seedlings in time. 5. Cultivation measures to prevent disease. It is recommended to use nutrient sputum or plug seedlings to raise seedlings. Seedling seedlings should not be too dense for seeding (the seeding is dense and easily lead to the spread of pathogens). Select seeds, fine sowing, cover soil should not be too thick, it is recommended to germination sowing. And time seedlings, layered on the soil. Rational fertilization, not partial application of nitrogen fertilizer, pay attention to the application of phosphorus and potassium fertilizer, the application of farmyard fertilizer should be fully decomposed. 3, seed treatment, use disease-free seeds 1. Before sowing, the tomatoes can be soaked in warm water (about 55 °C) for 15 minutes, which can control the pathogens on the seeds. 2. Chemical dressing: The choice of the agent should pay attention to both fungi and oomycete diseases. You can choose the drugs such as carbendazim, carbendazim, metalaxyl, mancozeb, and sclerotium according to the instructions. 4, pharmaceutical treatment The choice of agents is mainly carbendazim, chlorothalonil, dystrophin (metalaxyl), mancozeb, carbendazim, sclerotium, gray mold, diclosan, pulic and so on. The above is the main disease analysis and management points of tomato seedlings compiled by Huinong. The above-mentioned pharmaceutical solutions are for reference only and I hope to help you. 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