I am sure by now everyone has heard that they have found Southern rust on corn and Soybean rust on kudzu in southwest Georgia.
There has been a strong weather pattern of winds and rain blowing from the southwest towards us so it is possible diseases of all types could come in on a storm. I imagine that was the case for them with the Southern rust. I imagine Southern rust could show up here in the not too distant future. But don’t panic. I have attached some very in-depth information on corn foliar fungicides. Many appear to be very efficacious against Southern rust. Use it to help choose what you want to apply to control the spectrum of foliar diseases that concern your grower. Feel free to give that to growers, consultants, sales folks, etc. Next week I will try to send you a similar article on soybean fungicides.
A note of caution here. Common and Southern rust on corn and soybean rust are very different organisms. Just because a fungicide worked well against Southern rust on corn does not guarantee it will control your soybean rust. Be sure to check an efficacy table.
We have seen very little relationship between soybean rust occurring on kudzu and soybean rust occurring on soybean. We have seen extensive rust on a kudzu patch with no rust on an adjoining soybean field. Why is this?
- There are many strains of the rust fungus. Some appear to go to kudzu very easily but not so easily to soybean.
- We rarely see rust on soybeans prior to flowering in an individual field. I have been talking with folks in Lee County with group IV soybeans that have pods. That would be a good place to look for rust. A more conventional MG 5 or 6 field across the road that has not flowered probably would not have rust. But, it would be worth watching.
Highest risk fields for soybean rust are smaller fields but significant areas with trees on the east side shading the soybeans and holding the morning dew for long periods. Irrigated fields where the irrigation is run at night might be a higher risk than if you ran irrigation at midday. Its all about how long leaves stay moist if exposed to rust spores.
Jonathan Croft is leading our rust survey effort again this year. He will be assisted by “the rust King” Joe Varn who was unseated last year by the “new rust King” Rogan Gibson. Competition could be intense for the title this year. You are welcome to send leaves to any of those three or me if you suspect rust. Vigilance is our best weapon. One year we had rust in Horry/Marion county area before we saw it anywhere else in the state. It was all about weather moving up the coast that year.
More on soybean rust next week.
If you want to follow the survey efforts in Georgia and other states you can go to:
