There are 42 number groups of fungicide plus 4 letter ones which are then grouped by letter and number. The professional products have the groups numbers on them, but unfortunately the home gardener products do not. Now kerp in mind that these are ALL types of fungicides not just the ones for rust so don't rack your brain looking for all of them. Most things I have read for rust are these groups: 1, 11, 7, 3 (systemic) and M (contact).
The contacts don't have to be rotated just the systemics from what I understand.
Here is a link to the different codes. It has the class number/letter, group name, chemical name, and common name plus other stuff. If you know the active chemical ingredient in the product just look on the site for it and then you will know what group it's in.
http://ipm.ifas.ufl.edu/resour...
