Mold is everywhere. An integral part of the eco system, it's job is to decompose and break down organic matter. When a plant such as bamboo is sick, stressed or otherwise compromised, opportunistic mold can take hold and hasten the plant to its death. Mold is most aggressive during extended wet and cool periods. When you find black mold on your bamboo plant, you must act quickly to eradicate it.
Inspect your bamboo closely. You're looking for signs of sticky trails along the leaves and stems of the plants. If you find them, you've discovered honeydew trails. These were left by aphids, white flies or scale insects that feed on the sap of the plant. The mold covering these trails is commonly referred to as sooty mold. This mold can simply be wiped away with a wet rag. You must identify the pest growing on your bamboo plant and treat it with the appropriate insecticide. If you don't find any sticky trails, move on to step 2.
Observe the bottom of new bamboo shoots. If the majority of the mold is located there with a few patches on the culms, twigs and leaves, the culprit is likely culm smut. As the disease progresses, the twigs will swell, become stunted and produce black fruiting bodies. The only remedy for culm smut is to uproot the bamboo, as the fungus lives in the bamboo's roots. Burn the infected plants.
Observe the bamboo's leaves, culms and branches. If some parts of the bamboo are yellowed, dying and/or molded, then weak parts of the plant are being preyed upon by common mold. Prune away any yellowed, damaged, molded or otherwise-compromised parts of the bamboo plant. Don't be afraid to prune hard, as bamboo is the fastest-growing plant in the world. It will soon bounce back. Throw away the pruned material. Do not compost it.
Clean up any fallen bamboo leaves, culms and twigs from the bed. Mold often overwinters and reproduces on plant litter in the moist soil.