Originally Posted by Roslyn

Hi everyone,
I am growing several banana plants in a greenhouse and lately they have been developing big brown spots on the leaves, like this:

They are mostly pretty tall and from that particular picture, it looks like maybe the leaf has rubbed against one of the metal bars close to the ceiling of the greenhouse. Does anybody know if rubbing against a metal bar cause a brown spot that looks like that?

I don't think all of the brown spots can be explained away by rubbing against stuff though. I also have two young banana plants, maybe a foot or so tall, and they have brown spots on their leaves too:


One of the young plants even has brown spots on its cigar leaf:

There is nothing close to those plants that could have been rubbing against them. I have looked at some of the brown spots under a microscope, and I can't find any bugs or anything. Any ideas of what could be causing my problems? Thanks in advance. I am worried about my plants.
-Roslyn