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IPM Scouting in Herbaceous Perennials

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Thielaviopsis or black root rot
IPM scouting in herbaceous perennials > thielaviopsis or black root rot
Pathogen: Thielaviopsis basicola.

Hosts include: Digitalis, Gaillardia, Geranium, Lathyrus, Lupinus, Pachysandra, Phlox and Viola.

Symptoms: Stunting, yellowing and plant death. Symptoms are often mistaken for nutrient deficiency symptoms.

Spread: Thielaviopsis basicola produces spores that can persist for long periods of time in soil or on infested pots and equipment. Reusing contaminated equipment is a common source of disease. Fungus gnats and shore flies can vector spores.

Management: Do not reuse plug trays, flats or pots for susceptible crops. Keep good records of the production areas where there have been problems with T. basicola. Avoid growing susceptible crops in these areas for several years. Fungicide drenches should be used to protect very susceptible plants from infection.
Chlorotic foliage Chlorotic foliage
Chlorotic foliage caused by Thielaviopsis basicola. These symptoms are easily mistaken for a nutrient deficiency. At right, infected roots are darkly colored and rotted by black root rot.
Infected geranium Yellowing of phlox foliage Darkly colored spores
Infected geranium with poor vigor and dieback symptoms. Yellowing of phlox foliage caused by black root rot. Darkly colored spores of Thielaviopsis basicola have a distinctive morphology. Their thick spore wall helps them persist for several years in soil.
This information was developed from A Pocket Guide for IPM Scouting in Herbaceous Perennials by Jan Byrne and Raymond A. Cloyd. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2981).
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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Updated 9/28/07