By Loupylou
London,
United Kingdom 
Good day, what could be the white powdery substance I have on a red leaf dahlia, it comes off when wiped, but there are too many leaves to wipe. I have several of these dahlias but only 1 is affected. Any ideas as to what it is and what can I do ?
4 Sep, 2016
Answers
Yes, it's Powdery Mildew. Dahlias are prone to it. Although it doesn't look nice, it won't do the plant any harm.
4 Sep, 2016
Thankyou for your replys. Glad it will do the plant no harm as they are lovely.
4 Sep, 2016
Sounds like mildew. Spray with a fungicide and make sure the plant has enough water.
4 Sep, 2016