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Unusual Foliar Diseases Showing up in Iowa Corn

July 19, 2008
Image of light tan, round to oval spots characteristic of Holcus leaf spot

By Alison Robertson, Department of Plant Pathology

Over the past week I have received emails, phone calls and samples of two leaf spots that occur in Iowa from time to time, Holcus leaf spot and Physoderma brown spot.


HOLCUS LEAF SPOT

Holcus leaf spot is caused by the bacterium Pseudomonas syringae. Symptoms are light tan (sometimes almost white), round to oval spots, which may appear water soaked at the margins or have a light brown border occur on the lower leaves (Figure 1 and 2).

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