MSU Extension Integrated Pest Management

Root and stem rots

Pathogen

Rhizoctonia solani.

Stem lesions can develop in the canopy of closely spaced plants.

Hosts include

Achillea, Aconitum, Aquilegia, Aster, Campanula, Chrysanthemum, Coreopsis, Delphinium, Dianthus, Digitalis, Gaillardia, Gypsophila, Helianthus, Hemerocallis, Hosta, Iberis, Lathyrus, Lilium, Limonium, Lysimachia, Nepeta, Oenothera, Papaver, Phlox, Platycodon, Potentilla, Primula, Salvia, Sedum, Veronica and Viola.

Symptoms

Rhizoctonia causes a variety of symptoms, including damping-off, stem lesions, stem rot, root rot, crown rot and aerial web blighting. Infection causes wilting, stunting and possibly plant death. Some vegetatively propagated plants are susceptible to rot at the base of the cutting.

Girdling lesions on plugs caused by Rhizoctonia that infected plants at the soil line.

Spread

This is a soil-borne pathogen. It persists in soil as mycelium and sclerotia (small, brown, long-term survival structures). The disease is spread when contaminated soil, plant material, tools and equipment are moved.

Management

Good sanitation practices are important to minimize disease introduction and spread. Rhizoctonia spp. tend to be more prevalent on stressed or wounded plants. Stress factors such as an excess or deficiency of water and fertilizer are important considerations in preventing Rhizoctonia diseases. Avoid periods of wet conditions followed by dry conditions. The fungus is favored by warm, moist conditions. Severely affected plants should be removed promptly. Research on efficacy of biological control through soil amendments is ongoing.

Discrete brown lesions on roots of Echinacea.

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