Question
What is this disease, and how can I cure it?

Answer
 This may be the result of aphids on your tree.  They are known to leave a substance referred to as Honeydew on the lower leaves and on lower parts of the tree.  Normally the predatory insect population will keep them at bay but you can always wash them off with a plant wash or a new product called Atomic Grow.  [email protected]

It is allways a good idea to keep insect infestations off of your tree as they will reduce the potential of each leave to produce sucrose for the root system.  The more damage the leaves have the more energy your tree needs to repair itself and survive.

Good luck

James