Good evening, I have a mature Magnolia tree that appears to have some type of fungus. The leaves look wet and are sticky. There is a white powder on the botttom of the branches that appears to be like a fungal residue. The ground below the tree also has a sticky wet looking substance on it.
Dakota County Minnesota
This is definitely sounds like aphids. As they feed they excrete a sticky, shiny substance called honeydew. Ants are often found in trees that have a lot of aphids as they mine the honeydew for food.
One of the easiest ways for you to deal with this is to just hose the tree off as best you can with a hard stream of water. There are insecticidal soaps that you can use but a mature tree may be too big for you to use any labeled spray. Please follow directions on the chemical label.
If the tree is too large, it may be best to have a professional treat it for you.