Rice sheath blight, a fungal disease caused by Rhizoctonia solani, constitutes a growing problem for rice producers, particularly those operating in intensified farming systems. The disease has a dramatic impact on the health of infected leaves, causing them to dry out and die at an accelerated rate. Young tillers are not spared either, as they can be completely destroyed. One of the significant consequences of the disease is a significant decrease in the leaf area of the plant’s canopy, which directly leads to a reduction in yield.
Why Does Sheath Blight Occur?
The occurrence of sheath blight primarily depends on a few specific conditions such as high temperature (ranging between 28-32°C), a high application rate of nitrogen fertilizer, and a relative humidity level of the crop canopy from 85-100%. These conditions make the plant more susceptible to being infected by this disease. Moreover, the disease tends to strike with particular severity during rainy seasons due to the favorable dampness and moist conditions that rain provides.
Factors Facilitating Disease Development
A number of factors on and off the field contribute to the rapid development and spread of the sheath blight disease. An increased seeding rate or more closely spaced plants leads to a dense canopy, a perfect environment for the propagation of the disease. Along with these agronomic practices, other factors such as the presence of the disease in the soil and free-floating sclerotia or infection bodies on water also play a major role. Furthermore, the cultivation of high-yielding improved varieties seems to have an unintended effect of promoting disease proliferation.
Key Facts About Sheath Blight
| Fact | Description |
|---|---|
| Pathogen | Rhizoctonia solani |
| Optimal Temperature | 28-32°C |
| Relative Humidity Level | 85-100% |
| Nitrogen Fertilizer Level | High |
| Most Vulnerable Season | Rainy season |
Impact of Sheath Blight on Crop Yield
The onset of the sheath blight disease is detrimental to crop yield. While most of the plant’s energy is diverted into combating the disease, the reduction in leaf surface area hinders photosynthesis, ultimately leading to a lower crop yield. Apart from the leaves, young tillers too are affected by the disease, further reducing the overall crop output. Thus, to maintain crop yield, it is essential to manage and control the spread of this disease.