The leaves of banana trees are glossy green and shade-giving even when there are no bananas on the plants to pick. But age, weather, cultural problems and disease can cause the leaves to turn yellow and, if left unchecked, even die. While banana tree diseases rarely have a remedy, other problems can be solved with the help of proper diagnosis by a local agricultural extension specialist.
Banana plants don't tolerate cold weather well. Freezing temperatures will cause leaf damage, while long stretches of temperatures below 60 degrees down to freezing can cause problems ranging from fruit damage to leaf yellowing, wilting or dying.
Bananas are considered heavy feeders where plant nutrients are concerned. They grow quickly, and need plentiful nitrogen to keep up with their rate of growth. Lack of nitrogen often shows up as leaf yellowing, and extended periods without proper nutrition will cause older leaves to die in favor of younger leaves that might be able to recover once soil nutrition is more plentiful.
Panama disease (or banana wilt) yellows older banana leaves starting at the base, eventually killing them. It moves to gradually younger and younger leaves, and can kill the tree. Planting resistant banana tree varieties is the best remedy. Bunchy top is a viral disease spread by aphids that shows up in young leaves as stunting with yellowing and wavy margins. Banana black leaf streak disease starts as yellowing in the leaves, followed by black-brown spotting or streaking, and then the whole leaf blackens and dies.
Most cultural problems with bananas, such as heat, over or under watering or insect attack rarely turn the leaves yellow. While nutrition problems turn the leaves yellow, it is unlikely to cause death unless the problem is very severe. The most common reason for banana leaves to turn yellow and die, outside of cold weather, is disease. For this reason, it's important to grow disease-resistant banana varieties and send a sample of problem yellowing and dying leaves to an extension center for diagnosis. If your banana is diseased and you live in an area that grows bananas commercially, you will likely be advised destroy a diseased tree as soon as possible.