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Roslyn 04-13-2011 10:08 AM

Brown spots on leaves
 
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

Dean W. 04-13-2011 08:08 PM

Re: Brown spots on leaves
 
Maybe to much fertilizer (salt burns) just a guess.

Roslyn 04-13-2011 08:34 PM

Re: Brown spots on leaves
 
Do you know if there is a picture on here somewhere of what fertilizer burns look like on banana? I guess it could be possible for the young plants, because we did mix in a little slow release fertilizer into their potting soil when they were transplanted to bigger pots, but I don't think the big ones have been fertilized in a few months. Hmm...

Dean W. 04-13-2011 08:40 PM

Re: Brown spots on leaves
 
There is a search feature at the top of the forum. You can input a subject there and or similar threads are shown at the bottom of thread pages.

http://www.bananas.org/f310/burned-leaves-13130.html
http://www.bananas.org/f2/cause-burn...-dc-12341.html
Where are you located? The light intensity may be changing and causing some abnormalities. Sometimes plants burn or discolor behind glass or polycarbonate. Mine have been affected though seem to be coming back to normal after changes in the weather.

venturabananas 04-14-2011 12:27 AM

Re: Brown spots on leaves
 
Roslyn, I wouldn't worry too much about it. It isn't caused by disease. Seems like there are several potential causes of the kinds of burns you're seeing. You can get symptoms like you're seeing from too much dry heat, too much wet cold, too much fertilizer, too few micronutrients, premature emergence of the leaf, etc. None of these will kill your plant in the short term, though you wouldn't want to expose your plant to any of them in the long term.

If I had to guess, the burns on your cigar leaf are probably caused by too much fertilizer. Essentially what happens in that scenario is that the cigar leaf emerges in a premature state, in the sense that the cell walls don't have sufficient calcium and maybe other micronutrients to deal with the elements (sun, cool, heat, whatever). The same thing happens sometimes if you chop a pseudostem way back and so the cigar leaf emerges well below where it would have had the stem been intact.

The burns on the older leaves could be from just about anything. From what you say, it probably isn't from too much fertilizer. Perhaps they were in contact with something hot or cold.


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