(in South-Central Texas)
Unfortunatly, our hot humid climate is ideal for the development of several diseases that affect roses.   These include blackspot and powdery mildew.Blackspot--the most troublesome disease of roses in our area
Blackspot (Diplocarpon rosae) is the most devastating and widespread of the rose diseases. This fungus attacks practically all of our modern rose cultivars, but there are numerous wild roses which are left untouched!
Powdery Mildew--another widespread disease of rose
Powdery mildew (Sphaerotheca pannosa) is another widely distributed and serious disease of roses. Young tissues are the most susceptible and the disease is typically diagnosed when white, powdery patches of fungal growth appear on young leaves. These leaves will often fold inward or become twisted and distorted. New stem growth and flowers can also be attacked.