Cabbage clubroot, also known as nodule disease, is a fungal disease, which occurs in most parts of southern China and some acidic soil areas in northern China to varying degrees.

Symptoms and identification: Rhizomatosis mainly harms the roots of plants. At the early stage of the disease, local swelling appeared on the taproot and the first and second lateral roots, and the overground part grew slowly. The leaves outside often wither at noon and recover sooner or later. At the late stage of the disease, the nodules grew up, with the maximum diameter exceeding 10 cm, one or more of them varied, and symptoms such as yellowing of leaves, dry leaf edges and dry heartburn appeared on the aboveground parts. After Chinese cabbage plants were infected, the heading ability was weakened and the leaves were small and loose.

Control methods: ① control the source of seeds. Introduce seedlings in areas where clubroot never occurs, and strictly implement the quarantine system to avoid seed carrying bacteria. ② Improve the soil. When planting in areas where clubroot often occurs, slaked lime should be spread in the field 7 ~ 10 days before sowing or planting, and the dosage per mu should be 70 ~ 100 kg. Or in the early stage of the disease, root irrigation with 15% lime milk, 0.3 ~ 0.5 kg emulsion per plant. ③ Strengthening cultivation management. Rotation with non-cruciferous vegetables for 4-5 years, high ridge or high border cultivation. Increase the application of alkaline fertilizer, intensive cultivation, timely removal of diseased plants in the field, and bring them to non-water sources for destruction. ④ Chemical control. 75% pentachloronitrobenzene wettable powder, per mu 1.5 ~ 3 kg, with appropriate amount of fine soil, can be applied to the border before sowing or planting; Or use 75% pentachloronitrobenzene wettable powder 700 ~ 1000 times, and sprinkle it before planting, with 250 ~ 500 grams of liquid medicine per mu. You can also use 50% thiophanate-methyl wettable powder 1.5 ~ 3 kg, add a proper amount of fine soil, and apply it in the border before sowing or planting; Or water each plant with 400 ml of benomyl solution (gram of active ingredient) when planting, and then water it after 1 month.