Stem rot of flower seedlings

Stem rot of flower seedlings is a disease caused by fungi of the order Coleoptera. The disease can harm a variety of plants, and annual ginkgo biloba seedlings are the most susceptible, with a seedling death rate of more than 80%. In addition, it also harms the seedlings of pine, cypress, Torreya grandis, Pinus elliottii, Eucommia ulmoides, maple incense, Robinia pseudoacacia, chestnut, metasequoia and so on. After different seedlings are susceptible to the disease, the symptoms are different, but they are generally characterized by stem rot. For example, after the one-year-old ginkgo seedlings are infected, the initial symptoms are that the base of the stem turns brown, the leaves lose the normal green, droop slightly, and the disease develops rapidly upward, the whole plant dies and the leaves do not fall off. The cortex of the diseased stem is swollen and wrinkled, the epidermis is spongy or powdery, and the bacteria are immersed in the xylem, making the pith brown or hollow. After the disease extends to the root, it causes the root cortex to rot. For example, if the vaccine is removed, only the xylem can be pulled out and the root cortex will remain in the soil. If the biennial seedling is susceptible or the annual seedling has a mild disease, the aboveground part of the diseased seedling dies, and new branches can be formed from the base in the same year. In the hot summer, the soil temperature rises, and when the base of the seedling stem is burned by high temperature, the pathogen invades and harms. If the nursery land is low-lying and prone to stagnant water, the incidence of thin seedling growth will increase significantly. It is observed that seedlings generally begin to develop disease 10 to 15 days after the end of Meiyu, and then the incidence increases gradually, and the disease stops in mid-September. In order to prevent and cure stem rot, comprehensive control methods should be adopted: first, the land with low groundwater level and good drainage should be selected as nursery and container seedlings should be raised, and the nutrient soil free of pathogens must be used to adhere to the rotation system. the same kind of seedlings are not cultivated continuously in the same land; the second is to kill pathogens. Stem rot is a kind of indigenous pathogen, which usually lives saprophytic life in soil. Before raising seedlings, withered branches, withered leaves and hay can be evenly scattered on the seedbed, ignited and burned, which can kill pathogens in the soil. Can also be applied per mu of nursery land lime powder 25 kg or ferrous sulfate powder 15 to 20 kg to inhibit pathogens; third, the application of mature fertilizer. Fertilizers are mainly farm manure, supplemented by chemical fertilizer. Garbage compost, compost and barnyard manure may carry bacteria and should be composted and fermented before use. Generally, 40 to 50 piculs of rotten cattle dung are applied to each mu of seedbed. Using plant ash as base fertilizer, 50 to 60 piculs per mu, the fertilizer effect is good, and the disease prevention effect is also good; fourth, building a shade shed in the high temperature season can reduce the seedling bed temperature and reduce the incidence by more than 85%; fifth, improve the disease resistance of seedlings. Timely ploughing, weeding, interseedling and topdressing make the seedlings unearthed neatly and grow healthily. At the beginning of seedling emergence, the seedlings were sprayed with 50 to 75 kg Bordeaux solution per mu of nursery to form a protective film on the appearance of seedlings to prevent the invasion of bacteria. After the onset of the disease, remove the diseased seedlings in time, and sprinkle lime powder around the diseased seedlings to prevent spread. Planting pine branches on the nursery, or interplanting crops or green manure in the nursery, irrigation to resist drought also plays a certain role in reducing the incidence of disease.