I personally like to spray copper or make a tea with 1 gallon of water to 1 cup of organic corn meal (let sit overnight until it has a sweet smell, then spray). Neem oil sprays are good too. That is, of course, to spray after removing all of the infected foliage with clean scissors:-)

Why not use compost tea every three weeks or so? May slow it down a bit.

I use compost as mulch, and trim any suspect leaf/branch. Then I spray the leaves with compost tea. Top side of leaf, and bottom as well.