Introduction to the Latest Control Methods for Sheath Blight of Wild Rice Stem

Sheath blight of wild rice stem occurs in growing areas across the country. As its planting area continues to increase, the disease has become increasingly severe. Sheath blight damages the photosynthesis of wild rice stem, causing weak root absorption, and in severe cases can also cause the wild rice stem to rot and lodge. So how should wild rice stem sheath blight be controlled? Follow the editor and take a look.

1. Symptoms

Sheath blight mainly harms the leaf sheaths of wild rice stem, followed by the leaves. It is most likely to occur during the tillering stage and the pod-setting stage. It first develops from the leaf sheaths near the water surface, initially as dark green water-soaked spots, or gradually expands into round to elliptical lesions. The center of the lesion is light brown to grayish white, and dark green when humidity is high, while the edge of the lesion is dark brown. Later, multiple lesions overlap each other to form large tiger-stripe-like patches. The lesions extend from bottom to top to the leaves, causing lesions to appear on the leaves as well. In severe cases, they cause the leaf sheaths to turn brown and rot, causing the leaves to turn yellow and die prematurely. In humid environments, the lesions produce white spiderweb-like material and gradually wrap into cotton-like masses, which gradually spread into sclerotia the size of rapeseeds.

2. Occurrence Pattern

After harvest, the sclerotia fall into the field to overwinter, and these are the main source of inoculum for the disease the following year. A small number of mycelia and sclerotia overwinter on diseased residues and weeds. Sclerotia left on the soil can survive for 1-2 years, and the next year they spread through water flow. When the field is in a high-temperature and high-humidity environment, this disease is very likely to occur, and fields that are deeply flooded for a long time have severe disease incidence, while shallow water with frequent irrigation and alternating dry and wet conditions are beneficial to the growth of wild rice stem, so the disease incidence is lighter. In addition, the amount and timing of fertilization also have a certain effect on the occurrence and development of this disease. Applying too much nitrogen fertilizer in the later growth stage will cause the plants to remain green and grow excessively, resulting in a closed field canopy and increased humidity, thus creating favorable conditions for pathogen invasion and worsening the disease.

3. Control Methods

The most effective and simplest method to control sheath blight is to implement a water-dryland rotation of more than 3 years. Before planting, the inoculum source should be removed. After flooding or plowing and leveling in spring, a gauze bag can be used to collect floating debris mixed with sclerotia along the field edges and corners in the downwind direction, then take it out of the field to burn or bury deeply. This can effectively reduce the inoculum source, lessen the damage from sclerotia, and lower the disease incidence. At the same time, apply sufficient basal fertilizer, increase the application of decomposed organic fertilizer, appropriately increase phosphorus and potassium fertilizer, and avoid applying too much nitrogen fertilizer. During cultivation, plant at a reasonable density, promptly remove old leaves, yellow leaves, and diseased leaves, and improve field ventilation. In the early stage of the disease, spray fungicides such as carbendazim, sheath blight net, and thiophanate-methyl for control. The spray should be uniform and the dosage should be sufficient. An appropriate amount of laundry detergent can also be added to the spray solution, which helps the solution adhere to the wild rice stem plants.

The above is an introduction to the control methods for wild rice stem sheath blight. We hope it can help you. If you want to learn more related knowledge, please stay tuned to us.