I weeded and trellised my parents old rose bed (the bushes are probably 50 years old if not more) of climbing cecile brunners last year. They've been doing pretty good this year, lots of new growth, but are being attacked by powdery mildew.
I'm using bayer 3 in 1 care. Should I just keep applying it every 7 days till it gets under control? It actually looks worse after the first treatment, at least to me, is that normal?