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IPM Scouting in Herbaceous Perennials

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Didymellina leaf spot
IPM scouting in herbaceous perennials > didymelline leaf spot
Pathogen: Didymellina poecilospora.

Hosts: Iris; most severe on rhizomatous iris.

Symptoms: The first symptoms are tiny, brown spots with water-soaked borders. As disease progresses, the water-soaked areas develop into irregular spots with grayish centers and dark borders. Foliage is killed, weakening the rhizomes. Disease severity worsens after bloom.

Spread: Rain and splashing water disseminate spores to adjacent plants. The disease can easily be introduced on infected plant material.

Management: Good sanitation is important. Leaf debris should be removed in the fall to reduce inoculum, which overwinters on the dead foliage. If infected debris is left in the area in the spring, the pathogen can sporulate and reinfect developing foliage.
Severe blighting of foliage
Severe blighting of foliage. Most infections occur on the upper portion of the foliage.
Didymellina leaf spot Necrotic tissue
Individual spots with grayish centers and darker borders surrounded by yellow halos. Necrotic tissue coalesces around the leaf spots.
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