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Physoderma brown spot

Andrew Penney, Iowa State University PhD student in Plant Pathology, discusses the disease Physoderma brown spot.

 

Regional Crop Update June 25 to July 2

July 3, 2018 4:46 PM
Blog Post

Strong storms rolled across the state again bringing more heavy rain and even some damaging wind to areas. Despite the flooding in some areas and drought in the southern part of the state, 78% of the corn crop and 76% of the soybean crop was rated in the good to excellent condition based on Monday’s USDA Crop Progress Report. Iowa State University Extension and Outreach field agronomists share what they are seeing in fields across the state.

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Weather Conditions Ripe for Physoderma Brown Spot and Node Rot and Gray Leaf Spot

June 29, 2018
physoderma brown spot on corn

With most corn in Iowa at the V7-V12 range, it’s important to be aware of potential corn diseases at this particular time. Given the wet growing conditions over the last month, corn in parts of Iowa will be very susceptible to Physoderma brown spot and node rot, caused by the fungus Physoderma maydis, and gray leaf spot, caused by the fungus Cercospora zeae-maydis.

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Disease imposters

July 21, 2016 3:24 PM
Blog Post

This past week I have been busy with disease diagnostic workshops at the ISU Field Education and Extension Laboratory. For those of you who have attended my sessions before, you know that I usually have a quiz that consists of leaves with various diseases and disease look-a-likes or imposters. I thought I’d try and write a series of blogs pointing out differences between a disease and it’s imposters.


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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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