A ProMED-mail post
http://www.promedmail.org
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International Society for Infectious Diseases
http://www.isid.org

Date: Fri 3 Jun 2022
Source: University of Florida [summ. Mod.DHA, edited]
https://nwdistrict.ifas.ufl.edu/phag/2022/06/03/southern-rust-identified-in-corn-be-vigilant-scout/


Southern rust is one of the most concerning corn diseases for the area. It was identified recently in southern and central areas of Florida and southern areas of Georgia. Rainy weather has created a perfect opportunity for disease development. The humid conditions create a damp microclimate in fields providing conducive conditions for spores to germinate and infect plants.

Fungicides with mixed modes of action tend to provide better efficacy and more robust disease protection, as well as reduce the risk of resistance development.

[Byline: Ethan Carter]

--
Communicated by:
ProMED

[Southern rust (also called polysora or tropical rust) in maize is caused by _Puccinia polysora_. The fungus occurs in most tropical and subtropical regions and can cause significant losses of over 50 percent. Southern rust is favoured by warm, humid conditions. Leaves may die prematurely reducing photosynthetic ability; therefore infection before grain fill has been completed is more damaging to yield than infection late in the crop cycle. _P. polysora_ needs living host tissue for survival and spores are wind dispersed. No alternate hosts of the fungus are known. Resistant or tolerant ('slow rusting') varieties are being developed.

The related species _P. sorghi_ causes common rust of maize.

Maps
USA:
https://www.orangesmile.com/common/img_country_maps/usa-map-0.jpg,
https://promedmail.org/promed-post?place=8703769,106, and
https://free-printablemap.com/wp-content/uploads/2018/10/us-states-and-capitals-map-pertaining-to-united-states-of-america-map-with-capitals.jpg (with states)

Pictures
Southern rust of maize:
https://www.lsuagcenter.com/~/media/system/e/0/1/8/e01882b0016a677fae908b45d09ad540/rust2jpg,
https://crop-protection-network.s3.amazonaws.com/articles/photos/southern-rust-Adam-Sisson-35.jpg,
https://washington.ces.ncsu.edu/wp-content/uploads/2014/07/corn.png, and via
http://www.ent.iastate.edu/imagegal/plantpath/corn/southrust/

Links
Additional news story:
https://site.extension.uga.edu/colquittag/2022/06/southern-rust-found-in-georgia/
Information on maize southern rust:
https://cropprotectionnetwork.org/encyclopedia/southern-rust-of-corn,
https://cropwatch.unl.edu/plantdisease/corn/southern-rust,
https://doi.org/10.1007/s00122-006-0466-0, and
https://doi.org/10.1186/s42483-021-00102-0 (review)
_P. polysora_ taxonomy:
http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=179511
- Mod.DHA]

See Also

2010
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Fungal diseases, maize, wheat - USA 20100331.1017
2008
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Rust diseases, maize - USA: (NE) 20080814.2514
2007
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Southern rust, maize - USA (IA) 20071004.3276
Southern rust & ear rots, maize - USA 20070918.3096
2002
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Puccinia polysora, southern rust, corn - Argentina 20020205.3486

Website: http://www.isid.org

Published: June 10, 2022