It may be honey dew from bugs... likely aphids. check it very carefully for little critters - bottoms of leaves, any crotches of crooks.

http://en.wikipedia.org/wiki/Honeydew_(secretion)

Indiebookman, Thanks for the tip. I have noticed some little critters, don't know the real name for them but when we were kid we called them potato bugs, little scaled things that make your think of an armadillo. Not sure if that is the source. I have been picking them out. The seem to come out of the soil when I water. I am also noticing little spots of a chaulky substance on the leaves in places.