Control of Rhizoctonia Disease on Vegetable
Disease Detection
Symptom appears on the root of young plants and on the part near the soil, as well as on the leaves of mature ones.
The most common symptoms caused by Rhizoctonia are black rot of roots (Fig. 2), collar rot of seedlings (Fig. 3), sunken cankers of stem, sheath blight, and soft rot. Lesions on young plants often have brown color with water-soaked area near the soil that lead to damping-off or collar rot.
On older plants, lesions are lignified and dark- brown with sunken area near the soil. Leaves at the base of the stem in contact with humid, contaminated soil often suffer from soft rot.
Rhizoctonia likewise causes sheath blight on rice and corn (Fig. 4 and Fig. 5), and soft rot on cabbage (Fig. 6) and lettuce, with white mycelia appearing on the surface of the diseased area. Sclerotia is also sometimes observed.
Causes of the Disease
Diseases are caused by Rhizoctonia solani fungus, particularly sclerotia, that survive in the soil or crop residues for several years (Fig. 7).
Period of Disease Development
Rhizoctonia could appear on vegetables year round. However, it is most common in the spring season on such plants as cabbage, maize, and other vegetables.
Disease Control
- Plow at the depth of 8-13 cm so as to bury all the sclerotia and infected plant residues.
- Maintain water on the field for several days to minimize infection source.
- Screen for resistance to disease varieties.
- Regularly conduct phytosanitary and weed control to prevent the spread of disease.
- Adopt seed treatment by fungicide to increase seed germination and to protect young seedlings.
Index of Images
Figure 1 Rhizoctonia Disease on Cabbage
Figure 2 Black Rot of Roots
Figure 3 Collar Rot
Figure 4 Rice Sheath Blight
Figure 5 Maize Sheath Blight
Figure 6 Soft Rot on Cabbage
Figure 7 Sclerotia on Soil and Plant Residues
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