What causes this unsightly growth on my knockout roses? Knockout(06)

What causes this unsightly growth on my knockout roses? Knockout(06)

Video Screenshot Gallery: Kochanius Nude

Knockout Roses Holes In Leaves And White Spots at Richard Doolittle blog
Holes On Rose Leaves: The Known Culprits and Easy Fixes - A Garden Diary
Frost damaged plant hi-res stock photography and images - Alamy
Rose Slugs (Sawflies)- Identify and Treat - Plant for Success
What Is Eating My Rose Plant at James Aviles blog
Holes On Rose Leaves: The Known Culprits and Easy Fixes - A Garden Diary
What causes this unsightly growth on my knockout roses? Knockout
Knockout Roses Holes In Leaves TAFT Independent
Help identifying why my roses have white spots and holes. I've taken
Rose Bush Thrip Damage? - General - American Rose Society Forum