Symptoms of corn sheath blight

Maize sheath blight is a common disease in the whole country, and its harm is becoming more and more serious. So what are the symptoms of corn sheath blight? Let's take a look.

1. Main symptoms

It is mainly harmful to the leaf sheath, but also to the stem, causing ear damage in serious cases. At the initial stage of the disease, dark green watery spots were produced on the basal 1-2 stem node leaf sheath, and then expanded and fused into irregular or moire-like disease spots. The lesion is grayish brown in the middle and dark brown at the edge, spreading from the bottom up. The disease of ear bract also produces the same moire spot. The ear is bald after the disease, and the grain is finely flattened or brown and rotten. When severe, the basal tissue of the rhizome becomes grayish white, and the secondary root is yellowish brown or rotten. When it is rainy and humid for a long time, the disease grows into dense white mycelium, and the hyphae further accumulate into multiple mycelium, forming small sclerotia.

II. Ways of transmission

The pathogen overwinters in the diseased remains or in the soil with hyphae and sclerotia. Under the suitable conditions in the next spring, the mycelium produced by sclerotia germination invaded the host, and then the aerial hyphae were produced in the disease part, which continued to expand near the diseased tissue. When the mycelium invaded the epidermis of corn, the invasive structure was produced. Six days after inoculation, the mycelium spread longitudinally along the junction of epidermal cells, then branched longitudinally, horizontally and obliquely, the top of the mycelium became thicker, and lateral branches wound into clusters, which formed infection pads and appressorium close to the surface of the host tissue. Electron microscopic observation showed that the appressorium directly penetrated the epidermis of the host with hyphae or invaded from the stomata, and then expanded in the maize tissue. On the 12th day after inoculation, the hyphae were found in the inferior leaf sheath cells, some filled with cells, some penetrated the cell wall into the adjacent cells, making the protoplast granulated, and finally the cells disintegrated; 16 days after inoculation, AG-IIA protruded from the stomata of maize, and water immersion spots appeared in the leaves; 24 days later, AG-4 appeared disease on the bract and inferior leaf sheaths. Re-infection is carried out through contact with neighboring plants, and the disease is transmitted over a short distance.

III. Prevention and control methods

1. Remove the pathogen and turn deeply to eliminate the disease residue and sclerotia in time. At the initial stage of the disease, the diseased leaves were removed, and the leaf sheath and other affected parts were smeared with chemicals.

two。 Disease-resistant varieties or hybrids were selected, such as Yunuo 2 (Henuo × Hengbai 522), Benyu 12 and so on. Implement rotation, reasonable close planting, pay attention to trench drainage, reduce field humidity, combined with intertillage to eliminate field weeds.

3. Chemical control, soaking seed Ling according to the seed weight of 0.02% and then piling up for 24 hours for 48 hours. At the initial stage of the disease, 1% Jinggangmycin 0.5kg water 200kg or 50% methyl thiophanate wettable powder, 50% carbendazim wettable powder, 50% carbendazim Spray focuses on the base of corn to protect the leaf sheath.

4. It is recommended to spray transplanting Ling mixture at the initial stage of the disease. for specific methods, see the guide for the use of transplanting Ling mixture.