This actually brings up an interesting property discussion. Normally it's pretty clear when someone is doing something on their property that harms the environment of other people's property (e.g. releasing gases, etc).
In this particular case, it's your bees that are going onto the neighbors property and bringing back chemicals. Clearly you can't control the bees (unless you encase them in a dome) so it's not quite analogous to letting a dog roam around the neighborhood...
I'm very curious what would happen if e.g. you tried to sue your neighbor for harming your bees.
I've heard of a case where some guy put a pot with poisoned sugar water on his lawn to kill neighbor's bees and the other guy sued him. Don't remember what the result was, but it wasn't dismissed as obviously no-issue.
I imagine the lawyer you asked about it would roll their eyes.
There are restrictions on herbicides that can be used in most residential areas, I doubt you are going to get a court to override those rules and give bees priority.
In Sweden there are several court cases where the highest court have ruled in favour of beekeepers, due to benefit to the ecosystem. And fewer (don't know of any) against.
In this particular case, it's your bees that are going onto the neighbors property and bringing back chemicals. Clearly you can't control the bees (unless you encase them in a dome) so it's not quite analogous to letting a dog roam around the neighborhood...
I'm very curious what would happen if e.g. you tried to sue your neighbor for harming your bees.