Question
My mother in law lives on the Mississippi Gulf Coast and her banana plants (which are "fairly" old) develope black spots on the leaves which turn rusty and "take over" the entire leaf.  Any idea what this could be and a solution?

Thanks.

Answer
HI Bill...here are a few ideas as to the problem with the leaves.  
One could be chlorine in the water causing the other could be:
Eumusae leaf spot disease is caused by the fungus
Mycosphaerella eumusae. This pathogen is closely related to
the causal agents of two other leaf spot diseases, black
Sigatoka (caused by Mycosphaerella fijiensis) and yellow
Sigatoka (caused by Mycosphaerella musicola).
The disease was first recognized in survey samples collected
from South and South East Asia between 1992 and 1995.
It has since been discovered in Southern India, Sri Lanka,
Western Malaysia, Thailand, Vietnam, Mauritius and Nigeria.
Eumusae leaf spot disease is thought to be highly pathogenic,
as symptoms of this disease have been found in southern
Thailand and Sri Lanka on banana varieties resistant to yellow
and black Sigatoka.
WHAT DO I LOOK FOR?
Symptoms are similar to yellow or black sigatoka, with dark

So you have to be careful which variety of banana you purchase that does not get some of these diseases or if the water, you would have to let it stand 24 hours before watering it.