On Friday I found and confirmed NCLB in Calhoun County. I have found in corn in the V-5 to V-6 stage and also in corn in the V-10 to V-12 stage. Growers should be scouting there crops and be on the look out for NCLB. Northern corn leaf blight will not be a problem in every field, but in fields where it is a problem, timely use of fungicide program can protect yield. I recommend a combination of strobilurin and triazole fungicides is an important consideration.
Here are some words from Dr. Bob Kemerait, UGA Plant Pathologist, from earlier this month:
1. Jake found NCLB on some of his earliest corn (March planting date) that is now waist-high… It has been in the field a while. 2. The field is planted corn-behind-corn…. the spores (conidia) are still around from last year… 3. The field is planted to conservation tillage…. not only are the spores (conidia) still hanging around but they are in the crop debris exactly where we left them last year. 4. Rainfall has been abundant… hence greater splash of spores from the debris to the young leaves and also free moisture to aid in the infection process. 5. It has been cool….. the NCLB pathogen rages in temperatures between 64F and 81F…. sound familiar….
In other words.. we seem to have a perfect storm for northern corn leaf blight this year…….
So, what to do?
Question 1. Should every corn grower in the state of Georgia spray their corn at the 5th-to-6th leaf stage with a fungicide?
Answer 1. No, I don’t think that is necessary…. corn in fields with good rotation and where NCLB is not found when the fields are scouted certainly don’t need to be sprayed for this disease now.
Question 2. Well Bob, what fields would you spray early?
Answer 2. From our research, it is clear that IF NCLB is a problem in a field, it is important to apply a fungicide somewhere around the 5th or 6th leaf stage, preferably with a fungicide other than tebuconazole as I think we have better fungicides for this disease. This application is followed by a second application, somewhere around the silking stage. Growers who should consider this application are 1) NCLB is found in the field already, 2) Growers at high risk to NCLB (see description of Jake’s field…) and/or 3) the grower has very high expectations for yield and very low expectations for risk.
Question 3. What if the grower wants to spray early for NCLB but not too early…
Answer 3. In such case, the grower should continue to scout the field and consider risk factors and then decide just before it becomes too late to spray the field with a tractor-mounted-boom-sprayer.
Question 4. What about the early-tassel spray you always talk about?
Answer 4. I continue to encourage all corn growers with any reasonable yield potential to consider making a fungicide application at the early-tassel growth stage for management of southern rust. However, if our crop is disease free, which I doubt, then this application may not be needed.
Hope this helps,
Contact Brock, Nick, or myself if you have any questions.