Will mustard oil deter rabbits, or just kill my plants

It is more likely to kill your plants if you are spaying it on the plants. Hot weather will fry the leaves. Try bone meal spreaded around the plants (away from the root zone, or the roots might burn). Try a physical barrier, some sort of metal fence. that is the only sure shot way.

Try blood meal. We have at least a dozen bunnies a night munching on our yard at that is the only thing that has deterred them. It is good for your plants but you will have to keep applying it on a weekly basis. The nurseries also sell a deterrent made of rotten eggs but guess what? It smells like rotten eggs.

ive never heard of this method, but it sounds crazy enough to work.

mustard oil will definately not kill the plants ........just keep on using it unil the pests are tired of it..