I haven't used it this year because we just haven't ordered any but we used it last year and we use it all season long. I'm not sure why they say to stop when plants start blooming but it didn't bother the buds or blooms any.
There was research done and it documented what was used and what ratios was used but I can't find it on the internet at the moment. But if I remember correctly using Nickel Plus alone will not keep rust away, it was best used in conjunction with chemicals like Propiconazole and I can't remember which other ones.
Here is the abstract of one study done but I can't seem to find the full article
http://www.spcru.ars.usda.gov/...
