Rhizoctonia Root, Crown and Stem Rot — Rhizoctonia solani
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Host: A wide host range, including virtually all herbaceous greenhouse crops such as dianthus, impatiens, coreopsis, ageratum, chrysanthemum and petunia.
Symptoms: This disease is the most common cause of damping off of young seedlings. Older plants can show similar symptoms a brown to black canker at the stem base that often girdles and kills the plant. Dense plants under high humidity may show a web blight, where the fungus grows up the stem and onto the leaves.
Conditions Favoring Disease: Rhizoctonia does not need cultural errors to manifest; it thrives under typical greenhouse humidity levels and temperatures during spring and summer. High humidity at the media surface allows rapid growth.
How Pathogen Survives/Disperses: It does not produce spores but is moved from place to place along with particles of soil moved by water or wind. It can also be passed from greehouse to greenhouse on diseased cuttings, plants or worker’s hands.
Photo and write up provided by Syngenta Professional Products