I've been seeing large black ants going up a tree in my yard and I'm pretty sure they're carpenter ants. I can't see where they might be nesting because the tree is a huge oak. I don't want them killing the tree but I don't want to hurt the tree treating it. What can I use that's both safe and effective?
Carpenter ants will readily forage up a tree for food. Some of these trees will many times be prime locations for a nest. There is no doubt that over time an active carpenter ant nest will kill a tree faster than normal. To stop this from happening, there are two ways you can treat that are easy.
The simplest approach is to get some Carpenter Ant Gel and apply it to the trunk where they are traveling. Carpenter Ants will find it as they ascend the tree, feed and share it with their nest. This will ultimately kill all the ants. The second option is to treat the tree with some Termidor. Spray the trunk down so that any ants walking up the tree will have to cross the treated surface. This will shut the nest down as explained in our Carpenter Ant Control article.