The LSU AgCenter has a landscape trial of Knock Out rose varieties at Burden Center in Baton Rouge and also at the Hammond Research Station in Hammond. One piece of data that is collected regularly is blackspot susceptibility. We get many questions pertaining to how much blackspot do Knock Out roses get. Here are the blackspot data on six Knock Out varieties at Burden and all seven Knock Out varieties at Hammond from 2008.

Roses were not sprayed with any fungicide and were give “normal, minimum” care. Blackspot ratings are based on a scale from 1 to 6 where 1 = 0% foliage with disease, 2 = 1-10% foliage with disease, 3 =11-25% foliage with disease, 4 = 26-50% foliage with disease, 5 = 51-75% foliage with disease, and 6 = 76-100% foliage with disease.