A customer recently wrote:

“My husband and I were at your farm last winter and bought about 12 bamboo plants from you. They are all doing well, but I’ve notice on two of the clumps there are black areas around the base of the leaves where they grow out of the cane, and there are these large ants running up and down the canes. I don’t see any bugs, so I’m not sure why the ants are attracted to the canes. The ants don’t appear to be doing any harm, but they are only on the canes with the black areas on them. Do you know what this might be?”

I answered:

The problem you are experiencing on some of the bamboos is probably sooty mold. Sooty mold is a cosmetic problem that does not hurt the plants themselves. The black areas around the base of the leaves is caused by a nectar secreted by aphids. Ants climb up the culms to reach the nectar and take it back to their mounds. To control the sooty mold, you need to eliminate both the ants and aphids – no small problem in Florida. You can defeat the ants – at least for a while – by applying an insecticide like Spectracide granules or Amdro. You can also use an insecticidal soap to kill the aphids. There are various organic formulas available for this purpose as well. Please remember that this is a cosmetic problem. The plant will not suffer from the aphids or the ants climbing up the canes. We caution you to consider the effects pesticides have on the environment before unnecessarily applying them.