I first noticed discoloration within a few months of transplanting, but they might have been there from the start. Last year's culms shot up clean but have developed spots similar to those of the existing culms over the course of the year. See link below for pictures.

The bamboo is planted underneath mature oak trees and receives mostly filtered sunlight during the spring and summer months with only a few hours of direct sunlight. There is a several inch layer of leaf mulch covering the soil.

1. What is happening?
2. What can I do?

Thank you for any help you can offer.

Do all of the black spots form into the "holes", or do those dead areas form where no black was too? Some of it looks like animal damage (scratches or nibbles). When this year's shoots come up, try putting chicken wire around a few of the culms, to keep any squirrels, rabbits, or other critters from being able to touch the culms. (Make a 6" diameter "tube" of chicken wire -- don't have it touch the culms, but don't leave space so something can jump over or reach through.)