dying of new bamboo shoots

[Myro]

Hi,
I have a small planting of Yellow Groove bamboo, Phyllostachys aureosulcata. At time of planting it has only a few culms. Now, four years from planting it has 40-50 culms, 12 to 15 ft in height and up to 1" in dia. I put rhizome barrier 30" deep around the planting area. Rhizome barrier is 5 by 7 ft. and I put automatic irrigation system. Everything looks so good until this spring. In April or beginning of March almost 50 new shoots start to grow, but dozen of culms has died before it reaches two ft . Some of them was ten ft in height and almost 1 1/2" in dia and just died. Side branches become soft and fell off and in few days entire culm become brown. Rest of the plant looks good and 10 to 15 new culms is now 16 to 17 ft in height and 1 1/4" in dia and looks healthy. Does anybody has similar situation. Maybe It just need more fertilizer and water. Every advice will be helpful.
I will post some pictures soon.

[Kas]

Maybe too crowded. Try thinning out some of the oldest (usually the skinniest) culms to see if that helps next year. I read something about this in one of the bamboo books, but I don't remember exactly. I would look it up, but I got them from the library.

Kas