Question
We have about 20 mature photinias that provide a privacy hedge around our backyard.  Along with everyone else in VA, we battle a constant fight to save our photinias from disease (black spots, leaf "burning" and shrinking, all resulting in leaves falling off and if not treated, killing the photinias along with our privacy).  To battle the problem, I regularly spray in the Spring/early summer at the first sign of trouble, and I have pruned back the lowest branches so that none of them are touching the ground.  I just learned that I should have been picking up all the diseased leaves that had fallen, as the problem is a root disease, not a leaf disease.  We have ivy everywhere under the photinias as a means to avoid mulching, so it is very difficult to access and remove the fallen leaves.  I've done the best I can, but know that many remain.  I really don't want to remove the ivy and start mulching again, and we can't afford to replace all the photinias.  Any advice would be greatly appreciated!

Answer
Wendy,
While it is true that you should pick up and dispose of the diseased leaves when you can, it is not because this is a root disease in my opinion. The diseased leaves carry the spores of the infection, and therefore help to spread the disease and help it multiply. Some diseases re-enter a plant through the root system and others will wait until the conditions are right for them to release their spores into the air to infect the new growth.
I would say that if you are waiting until you see the first signs of a problem, then you are too late. Diseases such as leaf spot and canker need to be treated before the leaves are infected. You should be starting your fungicide treatments when the buds are starting to open up. This puts the fungicide into the juvenile leaves where it can block the initial infection of the tissue.
The best way to deal with disease problems, long term, is to change the environment to one that is not condusive to the disease formation. This can be done in many ways. The easiest is to not provide the moist conditions that the disease requires to grow. I would recommend that a soaker hose or drip irrigation system be placed under the Photinia at soil level. Clear away some of the ivy from the bases to allow more air circulation and make sure that the sprinklers that water your lawn are not wetting the leaves. This will help to make a more unfavorable environment for disease development.
If you are not already doing it, I would recommend fertilizing in the fall only. Spring fertilizations promote more growth than the plants can sometimes handle, while fall fertilizations promote stronger root growth and nutrient storage.
I hope this helps.