Lack of moisture would be reflected by browning of the leaves from the edges. Cercospora produces brown-to-purple spots throughout the leaves. It is not lethal usually but it just does not look aesthetically pleasing. If the spots look red, you may want to post a picture or take a sample to an Agriculture Extension Service for analysis. You could also try a nearby plant nursery but I have gotten mixed results with that (sometimes I find very knowledgeable employees but other times I do not). To minimize that problem, when I visit the plant nursery, I specifically ask for someone who can help evaluate a plant disease. Then I bring a sample in a sealed clear plastic envelope.

If you were to be doing overhead watering of the leaves, it may be that the leaves developed a fungal infection (sometimes just called leaf spots) and watering the soil and never the leaves will help. Other suggestions: water only early in the mornings; make sure there is separation between the shrub and others so air movement can help minimize fungal infections; opening some area of the shrub to light and air can sometimes help; discard leaves and plant debris in the trash; replace the mulch with new mulch. If the soil/mulch feels wet, reduce the amount of water and or frequency of waterings.

I have not heard of home grown fungicides for cercospora but there are some out there for Powdery Mildew which this does not sound like. It is imnportant to correctly identify the causal agent in order to apply a solution (fungicide, etc) that will correct the problem.

See if you can store a picture in www.photobucket.com or similar websites. They will give you a direct http link that we can then use to go and view the picture. You can simply copy/paste the direct link into a message just liek this one

http://i150.photobucket.com/albums/s111/llluch/100_4191.jpg

Luis

Here is a link that might be useful: Information on Cercospora

oakleafs do not like to be kept wet--they will wilt and die quickly from rot-keep water off the leaves....