As some of the corn around is starting to tassel, I am beginning to receive a few calls about when the best time to apply a fungicide is. The answer to that question is really dependant on a field by field basis. Some fields may need multiple sprays while others may not need to spray at all. Scouting the corn fields is the only way to know if you really need to apply a fungicide for NCLB.
Here are a few words from UGA Plant Pathologist, Dr. Bob Kemerait, on when you might think about spraying.
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 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.