During the summer of 2012, which was hot and dry, I observed river birch trees (Betula nigra) in northeast Florida with symptoms I had not seen previously. The leaves of new growth were smaller about 1/4 their normal size with a distorted, somewhat rolled distal end. Severely affected branches can defoliate and eventually die.

At first I suspected herbicide damage. But after seeing the problem on nearby properties that did not have the same landscape maintenance company, I ruled out herbicide as the cause.

I then remembered an obscure micro nutrient deficiency. It has a name — mouse ear. This rare micro nutrient deficiency is normally found on river birch nursery stock and less frequently in the field. This micro nutrient deficiency is more commonly found on pecan trees but I have not seen it on pecan trees in Northeast Florida.