Question
http://en.allexperts.com/q/Plant-Diseases-715/maple-tree-disease.htm   
I noticed that the answer you gave to this person about the gall disease on the maple tree was that it will not affect the overall health of the tree. My tree also has this disease, it is about 12 or 13 feet tall, still young and developed the disease this spring. Now, I have started to notice that the underneath of the leaves with these galls have big red blotched and are drying out. Is it the galls that are doing this or does my tree have another type of disease as well. The leaves drying out are the ones with the galls on them. Is there any spray of thing I could use to get rid of them.
Thanks

Answer
Onece the galls are formed by the  gall midge or mite there is no real way to get the insecicide to the "bug".
Look At this web link and you will see there is only a small window of opprotunity to get an insecticide to the young insect before it get incased in the gall. Although the leave of the tree may look real bad the over health of the tree is not really effected by the galls. Some leaves may fall off prematurely but there will be enough leaf surface left to produce food for the tree to grow. In general, these galls are not harmful to the health of a tree. The brilliant red color associated with these galls generally alarms some people who believe the trees are 揹iseased?or seriously damaged. Feeding by eriophyid mites appears to stimulate the formation of galls on the upper and lower surface of the leaves. Occasionally, photosynthesis (food making process by plants) may be reduced in individual leaves that are heavily infested. If many leaves on a tree are heavily infested, there may be some reduction in growth.
In general, leaf galls do not seriously affect the normal growth of a tree. Thus, chemical control is seldom suggested. If indicated, the best time to treat an infested tree with a registered insecticide applied according to label directions for management of eriophyid mites is mid-April, before buds swell. Adults move from their overwintering sites to new growth at this time of the year. This treatment may help reduce the eriophyid mite population on an infested tree. Application of some formulations of carbaryl (Sevin, etc) are labeled for control of mites on shade trees. However, because the galls do not affect tree health, applications are not necesary.
 
http://ohioline.osu.edu/hyg-fact/2000/2004.html