White weevils have been killing my plants. Have tried insecticidal soap and sevin dust
But to no avail. They like my roses, hibiscus and others

And them little bugs are smart, too. I mean look at one, and he runs around to the other side of the plant stem to hide. How could a little bug know I'm looking at him, and take evasive action? Even a fly isn't that smart. So they might have a lookout posted and be hiding from you and your sprays. Hibiscus is related to cotton, maybe try calling up Dept. of Agriculture in your county and see what insecticide they are using. Because this can vary depending on how big the problem is in your area.