Bayer 3-in-1 does suppress daylily rust, but the systemic insecticide (Imidacloprid) which comes along for the ride is very harmful to bees, and has been shown to persist in plant tissues for up to 6 months. I only use it on "non-flowering" plants and first-year daylily seedlings in their flats, and sparingly, at that.
For rust, get an appropriate fungicide. I've never liked the idea of multipurpose garden chemicals with tag-along insecticides—there are usually more negatives than positives. It's as if the manufacturers assume that the consumer is either stupid or lazy. It's also the logical result of "checklist" marketing. I think the worst example of this is when Imidacloprid is compounded with fertilizers. I always wonder how many people have inadvertently used it on their vegetable gardens.
The other problem with the all-in-one products is that when they become more popular, the individual components, (which are usually very effective chemicals) become hard to find in consumer-labeled products. For example, the miticide in Bayer 3-in-1 is highly effective, but it's not available separately. Actually, every component of the product works great, I just don't want to apply all of them when I only need one.
