How can we get rid of twitch without harming other plants?

welcome to GoY baltimore.
put on rubber gloves then a pair off old wool gloves. dip hands into weedkiller and gently rub your fingers over the leaves of the twitch grass. this will transfer the weedkiller to the plants and not spill onto the plants you want. Wash gloves thouroughly afterwards.
I have done this with bindweed before. it does work :o)

Thank you very much- will try this!

seaburn thats is brilliant. never thought of doing it that way.

Just make sure you don't get one drop on any of your precious plants