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IPM Scouting in Herbaceous Perennials

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Myrothecium leaf spot
IPM scouting in herbaceous perennials > myrothecium leaf spot
Pathogen: Myrothecium roridum.

Hosts: Lamium, Molucella, Rudbeckia and Salvia.

Symptoms: This disease causes leaf spots. Concentric rings may develop in the lesions. Raised, black sporodochia develop on diseased tissue. In high humidity, the sporodochia are encircled by a tuft of white growth.

Spread: Spores are splash-dispersed by irrigation water and rainfall.

Management: Avoid injuries to plants. Young or injured tissue is most susceptible. One common cause of wounding is packaging for shipping; disease readily develops following shipping. Avoid excessive fertilization – high fertilizer rates that favor lush foliage growth have also been associated with disease outbreaks. Reduce periods of leaf wetness by carefully timing irrigation. Fungicide applications may be needed to control severe disease problems.
Diseased tissue
Black, raised sporodochia on diseased tissue. Note that many are surrounded by a white tuft of spores.
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