been having problems all summer with some of my crape myrtle losing
its leaves. It looks like fall, the plants are half bare. The
leaves turn yellow, then dark and fall off. In addition, they
have not been flowering very much. I don't see any indication of a fungus. Attached
is a picture if that would help. About half of my crape myrtles
are having this problem. I live in the Woodlands, outside of Houston.
The problem started early in the summer during all the rain. While
the ground has been wet, it has not been holding water.
ANSWER: This looks like Cercospora
leaf spot to me. It is favored by humid climate, frequent leaf
wetness from rains, and poor drying conditions (crowding, dense
canopies, etc.), which occurred in much of TX in the summer of
2007. This disease causes yellow spots that eventually turn necrotic
and then defoliation is severe. The fungus is often visible only
with magnification (clusters of black conidiophores on the leaf
surface producing white to gray spores that may be quite obvious
after periods of high humidity.).
Mark C. Black, Extension Plant Pathologist
Texas Cooperative Extension