First of all, the subject should determine whether the root rot of cucumber seedlings is caused by non-bacterial infections such as insect pests, fertilizer damage, drug damage and retting roots. As long as one of them can be determined as the cause of the death of cucumber seedlings, it is not necessary to determine whether it is a disease. For example, cucumbers are grown in corn fields, and herbicides have been used in corn fields before. For example, the soil moisture is particularly high. For example, a large number of immature organic fertilizers were applied, and the roots were found to be bitten off.

If your land often grows melons and vegetables, I suggest you grow other crops. Because planting the same vegetable year after year will accumulate a lot of harmful bacteria in the field, which is not conducive to high yield of crops.

There are two main diseases that can cause the death of cucumber seedlings:

(1) Cucumber seedling blight: The base or middle part of the germ exposed on the surface of the seedling is soaked in water, and then turns yellow brown and shrinks into a line, often the cotyledons do not wither and the seedlings collapse. The hypocotyls and cotyledons of some melon seedlings were rotted, browned and died. When the humidity is high, white cotton-wool hyphae grow around the diseased plants.

This disease is caused by a fungal infection called pythium melonis. Low temperature and high humidity are easy to occur. It mainly happens when the seedlings grow to 1-2 true leaves, and rarely happens after the 3-leaf stage.

Generally speaking, if the soil is a vegetable field planted all the year round, it is best to carry out chemical seed dressing and soil disinfection. Disinfectants such as Dixintong, thiram and methylprednisolone can be selected. At the early stage of the disease, you can also use fungicides such as hymexazol and propamocarb to spray, but it is not suitable to spray when the weather is bad, and you can sprinkle powder instead.

Agricultural prevention and control is mainly to increase temperature and reduce humidity, and avoid watering the day before rainy days. Spraying plant ash on seedbed can reduce humidity and kill bacteria.

(2) Cucumber damping-off: It mainly harms the stem base or underground roots of seedlings. At first, the stem was oval or dark brown, concave inward and with obvious edges. After a week around the stem, the stem shrank and dried up, and the seedlings died. The roots are mostly infected near the surface, and the cortex is browned or rotted. Individual seedlings began to wither and died a few days later. It is difficult to tell the difference between the initial stage and the collapse, but the melon seedlings do not collapse, and there are wheel marks or not obvious light brown arachnoid fungi in the diseased area. It is different from the linear atrophy of damping-off disease and the failure of damping-off cotyledons to wither. This disease is caused by a fungal infection called Trichoderma cucurbitae. This is a soil-borne disease.

Pesticide control can choose soil spraying methylprednisolone, dixone, thiram, hymexazol, etc.