Question
In my neighborhood, there are plenty of Oak trees.  Many of them are oaks.  The Oaks, particularly White Oaks are suffering from disease.  The most prominent disease is one that I cannot seem to identify.  It is presumably a gall disease:  tiny white balls that are covering the underside of the leaf.  In many cases, the balls are so many that they litter the ground around the tree.  These white balls also cause discoloration.  


Another disease effecting the White Oaks in my neighborhood is not as common as the white ball disease.  It involves fungi-looking concave cup things on the underside of the leaves.  

I live in Montgomery County, Maryland, and am concerned about the White Oaks (these diseases are not effecting the Red Oaks, oddly) in my neighborhood.  Can you help me identify these diseases, and what causes them?   Thank you.

Answer
These are oak leaf galls made by an insect a small wasp usually. The insect lays its eggs on the leaf and secretes a chemical that causes the cells of the leaf to expand and cover the egg making a gall. the galls will not harm the tree's health but if there are many may cause the tree to drop its leaves sooner than normal. There is not need to control these insects.

Gall-forming insects include adelgids, phylloxerans, psyllids, gall midges, and gall wasps. Of the more than 2,000 galling insects in the United States, over l,700 are gall midges or gall wasps.

Galls are abnormal growths of plant cells formed in response to egg-laying by adult insects or feeding by immatures. Eggs are usually laid in actively growing plant tissue. The irritated plant tissue quickly surrounds the egg or immature insect, and protects and provides food for the gall-maker until it matures. Gall-makers may live in individual or communal chambers inside the gall.

The shape of each gall depends on which insect caused it to form. They may look like tiny blisters, round balls, tubes, or folded leaves. The gall surface may be smooth, hairy, or covered with spines.

The Maryland Forest Service has a office there in Montgomery Co They maybe able to ID the particular gall insect IF you really want to narrow the species down. Their contact information is

Montgomery County
17400 Annapolis Rock RD
Woodbine, MD 21797


(301) 854-6060
(410)442-2080
 Or you can contact the Pest management Section of the Maryland Forest service at
Forest Pest Management Section
email: [email protected], or call 410-841-5922

I am not sure what you wanted without seeing a picture of the gall it is next to impossible to specifically ID from the 2,000 different gall insects. It is not really that important to know the exact insect that is on these leaves but to understand that it will not in the long run adversely effect the health of the tree. Sorry you had problems with the answer.