Felum wilt, also known as Fusarium wilt, is distributed in various flax producing areas. Fusarium wilt mainly damages seedlings, causing lack of seedlings, cutting off ridges, and even destroying seeds; it also damages capsules, affecting seed germination rate and oil content. In the Bashang area of ??Zhangjiakou, a blight epidemic occurred in the 1980s, with an incidence rate of 80% to 90%, seriously threatening flax production.

Symptoms

After the seedlings become infected, the top leaves turn yellow and then wilt; the stems are grey-brown or tan, thin and constricted, and the base rots, withers and falls to death, as if Burning. The roots of the adult plant are grey-brown, the branch roots are necrotic, the underground parts are yellow and dwarfed, the leaves are wilting one by one from bottom to top, the top tips are wilting, the leaves turn from green to yellow from bottom to top, and the whole plant is withered and upright. The stems turn brown and the diseased plants die. The base and roots rot and are easily pulled out of the soil. The vascular bundles of diseased stems turned brown when cut open. Under humid conditions, pink mold often grows on the surface of the roots of diseased plants. During the fruiting stage, half of the tissue at the base of the stem is necrotic, half of the plant is wilted, the stem vascular bundles turn brown, root hairs and lateral roots are reduced, and it is easy to pull out; the seeds in the capsule are small and few, of poor quality, and the seeds are infected with bacteria.

Pathogen

Fusarium lini Bolley[=F.oxysporum f.lini (Bolley Snyder et Hanson)]. For the subphylum Deuteromycota, Fusarium linum. The hyphae of the pathogenic bacteria are well developed and spread within the vascular bundles of the host. They are colorless. Conidiophores are light brown, pink to red; conidiophores are produced. Conidiophores are short, branched, and clustered. Large conidia are spindle-shaped and sickle-shaped, with pointed ends and slightly curved. Single spores are colorless, and when multiple are gathered, they are light red. They have 3 to 5 septae. Those with 3 septae are 35 microns × 4 microns, and 5 septae. The size is 39 microns x 4 microns. Small conidial single cells, a few double cells, oval or oval, colorless, single cells are 8.2 microns × 2.3 microns, and double cells are 17 microns × 2.9 microns. The suitable temperature for bacterial growth is 26-28°C, and the suitable temperature for bacterial infection is 16-32°C.

Incidence characteristics

It is a soil-borne vascular disease. Overwinter as mycelium and conidia in the soil or on diseased remains. Mycelium lurks in the seed coat or conidia attach to the surface of the seed to overwinter, becoming the first source of infection in the coming year. The pathogen invades from root hairs or wounds, first invading seedlings, then repeatedly infecting in the field, and spreading to the capsules through wind and rain.

Prevention and treatment methods

(1) Crop rotation. Severely diseased fields should be rotated with crops such as grasses, potatoes, and sugar beets for more than 5 years.

(2) Agricultural measures. Strengthen water and fertilizer management, increase the application of base fertilizers, phosphorus and potassium fertilizers and compound fertilizers to improve plant disease resistance; promptly pull out diseased plants and collect diseased and residual tissues on the ground for centralized treatment; carry out deep plowing after flax harvest; it is strictly prohibited to apply diseased manure and use diseased plants Retting etc.

(3) Plant disease-resistant varieties. Such as Longya No. 7, Tianya No. 5, Nanxuan No. 24, Yannong No. 1, 228, Dingya 17, Hung No. 3, etc.

(4) Chemical seed dressing. The occurrence of seedling diseases can be controlled by dressing seeds with 0.2% of the seed amount using 15% or 25% of rosine powder.