http://www.google.com/url?sa=t&rct=j...67720277,d.aWw
Once a week 4 weeks in a row you will see the mold start to break apart. Neem is cheap
But you must spray under the leaves. then spray ground and other surrounding plants.. LOOK to see the insect causing the problem.. Good luck!
Also insecticidal soaps mixed with the Neem works well..
Bonide Insecticidal Soap Concentrate # 654, Makes 24 Quarts