SOUTHERN RUST ALERT
Below is a Southern Corn Rust Alert from University of Georgia Extension pathologist Dr. Bob Kemerait. Our corn crop has a very good to excellent yield potential. Growers should also consider a stink bug application with one pint per acre of methyl parathion 4EC or the high rate of a pyrethroid if they are going to make a fungicide application.
Greetings: Southern corn rust (Puccinia polysora) is confirmed for the first time in Georgia in 2012 from images sent by county agent Rome Ethredge. Thus far the southern rust has only been found in a single field that is south of Donalsonville. The rust is active in a “hot spot” but symptomatic plants are not found widely in the field (yet).
The affected area is planted to Pioneer 1814, so it is impossible to determine from this find whether we have the “old race” (Rpp9-sensitive) or the “new race” (Rpp9-virulent). The field was sprayed 4 weeks ago with a tank-mix of 6 fl oz of Headline and 4 fl oz of Tebuconazole (I would expect the protective window to be no more than 3 weeks); the field will be sprayed again tomorrow with 12 fl oz Quilt Xcel.
1. I don’t think any of us are surprised to find southern corn rust now; ESPECIALLY after the passage of TS Beryl. (Good job Rome!). Based upon the amount of rust in the field, it is very possible that the initial spores rode the winds of Beryl.
2. Southern rust has appeared MUCH MUCH earlier this year than it did in 2011!
2. Conditions are VERY favorable now, have been for the past 3 days, and will continue to be favorable for the next week for further development and spread of this disease.
3. Growers currently at greatest risk to southern rust are those in southwestern and south-central Georgia; we continue to scout sentinel plots for further spread.
4. Growers who should weigh the importance/need for a fungicide application in the near future are those: a) in SW and SC Georgia; b) good yield potential, c) the crop has not reached dough stage, and d) the crop has not been treated with a fungicide within the past 3 weeks.
5. Triazole fungicides and strobilurin fungicides all have good activity against southern corn rust; triazoles will have greater systemic activity; strobilurins a longer protective window.
The battle is here. Below are photos of Southern Corn Rust from Seminole County Extension Agent Rome Ethredge: