Southern Rust of Corn
Written by Madeline Henrickson
7/15/2019
Written by Madeline Henrickson
7/15/2019
Puccinia polysora pustules on a corn leaf.
Southern rust pustules on a corn stalk.
Figure 1. Life cycle of southern rust (Puccinia polysora).
Southern Rust Has small circular, pinhead-shaped pustules.
Coloration of pustules/spores is reddish orange.
Only infects the upper leaf surface, not the undersides of leaves.
Optimum temperature is warm-hot (over 77 ºF, 25 ºC).
Common Rust. Has larger pustules that are more elongate and blocky.
Coloration of pustules/spores is brown to cinnamon-brown.
Infects both the upper and lower leaf surfaces.
Optimum temperature is cool-warm (60-77 ºF, 15-25 ºC). .
Figure 2. Confirmed detections of southern rust in corn through the first week of September during the 2017 and 2018 growing seasons. (Source: http://www.ipipe.org).
Southern rust symptoms visible in the upper canopy of corn in Johnston, Iowa (Sept. 11, 2017). Foliar disease was extensive but infection occurred late enough in the growing season in this instance that yield impact was likely minimal.
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