Question
I planted about 10 cottonless cottonwoods on a fence line 15 months ago. Their growth has been tremendous. In the past several weeks however, their leaves have developed dark spots on them and are turning yellow. Is this normal or is it some kind of desease that can be treated? I am just outside Houston TX.

Answer
More than likely it is a spot fungus. You have had a unusual amount of rainfall this year and this allowed the fungus to grow much better than normal. Any fungus that infects late in the year is considered not a real health problem due to the fact that the trees will soon start to shut down for the fall and begin drooping the leaves. No need to treat the leaves with anything now. I would really consider this "normal" for cottonwoods. You can rake up the leaves when they fall and destroy them this will cut down on the fungus spore next year. If it were me I would not worry about them.