Common root diseases of vegetables

With the decrease of air temperature, the temperature in the interior of the shed will drop day by day, and all kinds of root anomalies will occur in varying degrees. (take tomato as an example)-Fusarium wilt, root rot, bacterial wilt and root knot nematode are common root diseases. In addition, a variety of deficiency and knotty abnormalities on vegetables are also related to root absorption. 1. Bacterial wilt. Symptoms of bacterial wilt: from the appearance, the main feature of bacterial wilt is plant wilting. After the onset of the disease, it showed that the upper part of the top wilted in a good day, and then the lower part was infected to the middle, some of the branches wilted first, and some of the whole plant wilted. For a tomato with wilting symptoms, if you cut off the base of its stem, you can clearly see that the vascular bundle inside has turned brown. It is precisely because these vascular bundles have been destroyed, so that nutrients and water can not be transported upward normally, which makes the tomato wilt. Experts point out that if tomato bacterial wilt is not treated in time, it will wilt several times repeatedly, resulting in dead trees, causing great losses to vegetable farmers. The best way to deal with tomato bacterial wilt is to use medicine to irrigate the root. 2. Fusarium wilt. Symptoms: the disease is a vascular bundle disease, which begins to show after planting. At the initial stage of the disease, the leaves close to the ground turn yellow, and finally turn brown and die, and most of the withered leaves do not fall off on the stem; in the early stage of the disease, the leaves on one side of the stem turn yellow, and the color of the leaves on the other side is normal; there are also leaves on individual branches, half of which are yellow and the other half is normal. When the disease was serious, the diseased leaves spread from the bottom to the top, and finally only the top leaves remained, and the rest withered. If the disease is mild, it is only close to the ground, except for the yellow leaves, the rest are normal, and there is no difference in flowering and fruit between the healthy plant and the healthy plant. The root of the diseased plant is brown rotten or local necrotic. The vascular bundles at the base of the stem are yellowish brown. The main difference between the disease and tomato bacterial wilt is that the leaves are withered and yellow after the disease. Damp often produces pink mildew (fungal conidia) at the base of the stem. The law of occurrence and development: it is the most easy to occur when the ground temperature is about 28 ℃, high soil water content or more soil root-knot nematodes, resulting in wounds due to root dysplasia, which is beneficial to the incidence of Fusarium wilt. The pathogen only infects tomato, and the number of pathogen increases year by year, and the disease occurs seriously. 3. Root rot. Symptoms: the disease harms the stem base or root. Brown plaque is produced at the beginning of the disease, which gradually expands and then depresses. In severe cases, the disease spot surrounds the base or root of the stem for a week, resulting in the gradual withering of the aboveground part. Longitudinal section of the disease, it can be seen that the duct is dark brown, the posterior rhizome is rotten, does not grow new roots, the plant withered. Occurrence regularity: according to relevant data, the pathogen of root rot overwinters in the soil with the remains of the diseased plant, or it is possible to winter in compost that is not fully mature, and a large number of molecular spores are transmitted by Rain Water or irrigation water in the following year, which is conducive to the disease in high temperature, high humidity or low ground temperature. After tomato planting, if the ground temperature is low, the soil moisture is too high, and the duration is long, or the continuous overcast and rainy greenhouse fails to ventilate in time, resulting in high temperature and high humidity in the greenhouse, especially after flood irrigation, the ventilation is not timely, it will lead to the occurrence and epidemic of the disease. 4. Root nematode. Damage symptoms: mainly occurs on the fibrous root and lateral root of tomato, cutting the root knot has a very small milky white nematode hidden in it, the new root on the root knot will be infected again, and form a root knot tumor, the serious plant morphology is short, stunted, even premature senility and death. When the soil temperature is 25-30 ℃ and the soil water content is 40%, the pathogenic nematode develops very fast, and the larvae stop moving when the soil temperature is below 10 ℃. Its secretions stimulate cell proliferation and form root knots or nodules. The solar greenhouse with dry soil and loose soil texture is suitable for nematode activity, so the disease is serious; the disease of continuous cropping is serious. This nematode is mostly distributed in the area where the root of the vegetable is located, in the topsoil layer of 3-10 cm. In addition, there is also the manifestation of element deficiency in vegetables, which is not necessarily due to the lack of this element in the soil. it is caused by the decline of root absorptive capacity caused by a series of problems, such as soil consolidation, inappropriate soil pH, or uneven soil water supply. 5. Soil consolidation leads to root abnormality. Soil hardening, root system can not develop normally-soil aggregate structure is an important index of soil fertility. The destruction of soil aggregate structure reduces soil water and fertilizer retention capacity and permeability, resulting in soil hardening. Vegetable roots in this state will decrease their vitality due to lack of oxygen. Therefore, in normal agricultural management, avoid flooding irrigation and try to adopt irrigation methods with less impact on soil permeability, such as drip irrigation is both scientific and water-saving. In case of rainstorm and other flood irrigation shed, it should be drained in time. It is suggested that in vegetable fields or shed rooms which are not covered with plastic film, hoe should be carried out after irrigation, which can not only increase soil permeability but also reduce soil water evaporation.