Corn is really progressing. We’re past tassel in most fileds and through milk stage (R3) in this field. Looking at corn yesterday, I noticed some leaves with rust postules which later confirmed to be southern rust.
Initially, it looked similar to common rust, which we do not worry about. But there were no postules on the back of the leaf (as with common rust). Plus, our hot temperatures are more conducive for southern corn rust.
Southern corn rust has appeared at least 2 weeks earlier in 2014 than it did in 2009, 2010, 2011, 2012 or 2013. Appearing earlier means that this disease will likely be more problematic in 2014 than in recent years – and it has been. Below are comments from UGA Pathologist, Dr. Bob Kemerait:
Sporadic afternoon and evening thunderstorms are likely to further move rust spores and also provide the moisture important for infection.
- I believe that this is the most significant threat of southern rust in Georgia in the past 10 years.
- Southern corn rust (SCR) reduces the photosynthetic capacity of infected leaves. More importantly, a field where SCR is not controlled may develop extensive lodging problems as the stalk is cannibalized for nutrients to feed the ear.
- Dr. Dewey Lee and I agree that protecting a crop from rust though the dough stage (R4) is beneficial.
- I recommend that growers spray by tassel growth stage and then again 2-3 weeks later, depending on the product used in the first application.
- On corn where rust is a severe problem, we have seen fungicides protect 25+ bu/A.
Southern corn rust has been on the move and covering many counties across the state. Here is the current map on its location: (http://scr.ipmpipe.org/).