The recent wet, unseasonably warm weather has lots of insects on the move. Most of them don’t matter much to pecan growers, but fire ants can be a different story. That’s especially true if the ants build their mounds inside the guards used to protect young trees from herbicide applications. Filling the tubes with dirt is a bad thing for the trees and also makes any control difficult or impossible. The problem can occur in any orchard setting but is particularly common in low-lying sites. The ants are trying to get up above grade to stay dry, and the guard tubes make piling the dirt up easier.
Unfortunately, there really is no solution that doesn’t involve removing the guards. Even pouring insecticide directly down the tube won’t always do the trick – it takes a lot more liquid than most people think to drench all the way down to the bottom of the underlying mound, and the dirt would still be there. The guards protect the ants from orchard floor sprays just as effectively as they protect the tree trunk from herbicide sprays. If you leave the guards on the problem is likely to continue as long as the weather stays warm and wet (a typical south GA “winter”). Once the guards are off, an orchard floor spray with chlorpyrifos will reduce ant activity and mound building as long as you pick a time when the ants are active (put a little bit of peanut butter or tuna out near a mound to check for activity. They’ll be on it 5-10 minutes if they are). Follow that up with a bait application in the spring and early fall to reduce fire ant populations before the winter season next year.
At the very least, you need to remove the guards from trees with mounds already in them. It’s not the ants that are the problem, it’s the dirt. Six inches of dirt inside the guard means your tree is effectively planted 6” too deep, and the graft is probably underground. Especially for very young trees, that is a real problem.
Prepared by: Dr. Will Hudson