Q.What Could Be Killing My Neighbor’s Bamboo?
The sad truth is my neighbors of 26 years are accusing me of poisoning their bamboo which goes half way across their yard. They used to be completely reasonable people. I have included some photos

Certified GKH Gardening Expert
These articles should help:
https://www.gardeningknowhow.com/ornamental/foliage/bamboo/bamboo-plant-diseases.htm
https://www.gardeningknowhow.com/ornamental/foliage/bamboo/yellowing-bamboo-leaves.htm
https://www.gardeningknowhow.com/ornamental/foliage/bamboo/bamboo-with-brown-tips.htm
https://www.gardeningknowhow.com/ornamental/foliage/bamboo/bamboo-mite-information.htm