Question
I have 2 holly bushes, one on the north side of my lawn which is affected. The leaves are turning yellow, with large black spots. and in addition, some have small white spots outlined in black. These leaves fall off. The bush is about 3 years old. Last year was the first year that I have had a problem. The other holly on the south is OK.

Answer
There is a fungal disease called tar spot that causes the black spots with the yellowing and can cause defoliation.  The white spots outlined in black do not sound familiar to me.  If the white spots can be rubbed off with your fingernail, I would think they were scale insects.  I would first make a determination as to whether you thought the problem was mostly fungal or an insect.  If you suspect fungal you can treat with the fungicide Spectro 90, which should be available at most good garden centers.  If not available buy Daconil fungicide.  If there are also insects involved, you will have to treat with an insecticide.  I recommend Bayer Advanced Tree and Shrub Insecticide which can be bought at most big box stores.  The product is mixed with water and poured on the soil around the base of the plant.  It is systemically taken up by the plant and kills the bugs.  It prevents re-infestation by insects for up to 8 months.  Also clean up all fallen leaves as these will serve as a source for both the fungus and the insects to re-infest the plant.  I hope these suggestions solve your problem.  Good Luck.