Security cameras to catch them doing it. Guess they aren't the type you could chat with about it are they?

@JC1965 : I see your picture is from a security camera. Do you have footage of them spraying on purpose? Looking at their yard, it's hard to imagine why they would object to your plants and try to kill them. People are nutty, though.My idiot neighbor used a spreader for granular weed killer and it went into my very large flower bed....everything has looked horrible since. He didn't do it on purpose, he was just ignorant and lazy.

Put up a fake bamboo fence along the iron fence and hope?

put one of those video surveillance signs up facing their home so they can clearly see it. Years back I had a neighbor letting air out of my tire. Took tire to shop and no leak. wake up flat. air up repeat. so I clearly made it clear while he was in his yard that I was putting up a camera ( 5 dollar fake with battery operated light) facing my car . While he watched the install from his porch. Ya know what? Never had another flat tire ! As$ H@L*

@JC1965 : Should have taken them to small claims court

1) if you feel they would be approachable, discuss your concern with them
2) consult with your HOA to see if the pay have any advice (they may be aware of a similar situation from the past)

I don't really blame them regarding the bamboo plants - those things are horrible and will at some point be growing over on their property. They are impossible to get rid of and invade everywhere. HOA's should require no bamboo should be planted at all. I've been to several HOA meetings in the past where someone is complaining about bamboo growing under the fence line and messing up the whole wooden fence and they expect the HOA to take care of the matter which is not how that works so to avoid this just ban bamboo completely

return fire

@ginx : thank you. I wondered if these existed? If I put up a sign warning this is present am I liable for the dog walker that gets sprayed while allowing their animal relieve itself on my front lawn?

@JC1965 : I experienced the sewer problem. Mine did the same but was all mine. big company's quoted 10 to 12 grand for all crazy deep trench .lots of concrete patio to break up. After a few cleanouts to get us through and smaller company's coming in at under10 grand I stumbled upon Doug Street at our church who happened to own " Alpha- Omega plumbing" After some thinking wound up not necessary to break up the patio and that section was fine. Turned out right off the patio the builder who installed the inground pool decided to use a lower guage piping to reroute the sewer resulting in a failure. man o man. lots of HAND digging and 1500 bucks later we were good to go! Shout out to Alpha-omega plumbing !

Oh and the crappy neighbor is still crappy after telling me " well if we were friends like neighbors should be I would have helped on the fence replacement, but now it`s all yours. All this comes from a while back when we were having a real problem with westnile virus and I asked him if I could drain, clean and refill his smelly green kids pool in his backyard . It was a concern for us.