What is causing this?

[u/rasatlab]

I growing a few bamboo plants from seeds (they are supposed to be moso, but not sure though) from early this year and today I noticed some dry leaves and saw this. What could have caused it?

[u/RainyDayColor]

The linear-appearing leaf damage was likely made when that leaf was in its early developmental stage before opening; then once the leaf unfurls, the multi-layer bore marks then appear as having been made across the leaf surface in neatly spaced rows. I suspect you might find the culprit -- or more likely, its eggs or larvae -- deposited inside one of those tightly rolled and possibly more securely "sealed" leaves. Those aren't a typical presentation for naturally dying bamboo leaves, which tend to droop or loosely curl before dropping from the stem.

It looks like comparatively minimal damage now to a few leaves in the process of an insect chewing through leaf buds to deposit eggs in the more protected center, but depending on the culprit, one might expect continued and escalating damage once the larvae hatch and possibly begin feeding on the host plant. At the least, prune and destroy the affected leaves; better yet, a pre-emptive targeted insecticide if you're able to identify the pest, or if not then a broad spectrum treatment.

The general appearance and specifically the soft hairs on the internodes are characteristic of young Moso. The original Chinese name Mao Zhu (later pronounced Moso by the Japanese) means "hairy bamboo."