Expert: Mike Mascio - 7/1/2009

Question
I live in the Saint Louis area.  Recently my hanging baskets filled w/ wave petunias have developed little black bumps on the leaves.  Other than these little black bumps the plants seem to be in pretty good shape.  I have the baskets hanging on my front porch where they get morning sun.  Any suggestions on what these bumps may be and what may be causing them?  If so, how do I treat the plants to rid them of this problem?  Thank you in advance for your help.

Answer
This could be the onset of black spot, a fungus disease that crops up when the weather is humid.

You can prevent this by praying the plants with an all-purpose fungicide. I use a product called Soap Shield, a copper-based fungicide sold by Gardens Alive. Attached is a link in case you are interested.

http://www.gardensalive.com/product.asp?pn=8066&ss=Soap%20Shield

I hope this information helps. Good luck, and please write again if I can ever provide assistance.

Regards,

Mike