By Clint Thompson
Increased rains in the Southeast means pecan growers in Georgia and Alabama are applying fungicide treatments for scab disease with greater frequency. That means greater potential for Miravis Top to be overused despite being susceptible to resistance.
Lenny Wells, University of Georgia Extension pecan specialist, cautioned producers about overusing the highly effective fungicide.
“One issue we have is that there’s a lot of pressure on with Miravis Top. With it being such a good product, a lot of growers get stuck where they really want to lean heavily on Miravis Top,” Wells said. “It definitely needs to be a part of that nut scab program, but that product hasn’t been around that long. One of the components of it is that it’s a Group 3 fungicide, and those Group 3 fungicides are much more prone to resistance than we’ve seen in some orchards.”
UGA Research
Wells cited work done at UGA by new plant pathologist Clement Oliviera and retired scientist Tim Brenneman. Both have documented a shift in recent years in the insensitivity of scab to Miravis products.
“That’s not to say that it doesn’t work, because it still works great. It’s just a strong indicator that growers really need to be careful about not overusing that product and making sure they rotate it so that we can steward that product very well; so that it’ll continue to work for us for years to come.
“If they overuse it or don’t rotate it, then it’s not going to be with us too long.”
Scab is a fungal disease that infects the leaves or nuts of pecan trees. If scab impacts the nut early enough in the production season, it can cause the nut to blacken and fall from the tree. It excels on trees that have received moisture. Some growers must make at least 10 fungicide applications during an average year to manage the disease.
It would devastate the pecan industry if it loses Miravis Top to resistance development.
“Absolutely, we don’t need to lose one, because we’re limited on what we have and losing one, especially one as good as Miravis Top has been for us, would be a difficult pill to swallow.”