10 year old clumping bamboo dying
Thank you for your question. Although the most common method of killing most plants is the herbicide glyphosate (sold as Roundup), you would need to have the soil and plants tested for that at a commercial laboratory. I am not certain whether the OSU Plant Clinic tests for that (http://plant-clinic.bpp.oregonstate.edu/services-and-fees/). However, if he were applying any herbicide to his side of the fence on plants that had developed from yours onto his property, it would require you to discuss any legal redress with an attorney, since the law is unclear, at best, on his rights to keep an invasive species out of his yard. Good luck!