"My knockout roses are being eaten by the Japanese beetles. Why doesn't the rose food with systemic insecticide bother the beetles? Thanks." -- Lynn
For systemic insecticides to be strong enough to kill Japanese beetles, they would kill the roses first.
Have you tried hand-picking the beetles? Do it early morning. Sneak a container with soapy water under the leaves with the bugs and the bugs will fall into your container. If you get them early enough, they won't leave a trace pheromone for other beetles to follow.
You can also try wrapping your roses in cheesecloth or fruit tree netting.
Let me now what ends up working best for you. The good news is that they only live for about six weeks. Good luck!