Southern Rust of Corn Map
Southern rust is caused by the fungus Puccinia polysora and can occur in important corn production areas of the United States and Canada. It can be difficult to distinguish common rust, from southern rust. We recommend submitting samples to an accredited diagnostic laboratory for confirmation. Counties or parishes that are highlighted in red on the map have had southern rust confirmed by University extension personnel and/or diagnostic laboratories.
Note that the map may display “gaps” where active monitoring and scouting for southern rust may not be occurring. If southern rust has been identified in a county/parish, this should encourage you to scout your fields for this disease. Confirmed southern rust does not necessarily mean a fungicide application is needed in that area. For more information about management of southern rust, please read An Overview of Southern Rust, including Table 2, which provides possible benefits from applying fungicides based on when southern rust is first detected in an area.
Crop Stage When Southern Rust is First Detected | Possible Benefit from Spraying | Comment |
|---|---|---|
Vegetative | Not likely to find southern rust at this stage unless corn is planted very late for the region | Scout fields for disease |
VT (tasseling) | Yes | May need a second spray |
R1 (silking) | Yes | May need a second spray |
R2 (blister) | Yes | Less likely to need a second spray |
R3 (milk) | Yes | No second spray needed |
R4 (dough) | Maybe, with severe disease pressure | No second spray needed |
R5 (dent) | Unlikely | No second spray needed |
R6 (black layer) | No |