· Brent Wilson's Answer
· I agree with Brooks and don't think that a single over watering would cause this problem. In it's native region, Nuttalli oak grows in lowland areas...but not permanent swamps. This means it likes moist soil, but it will tolerate periods of drought.To cause damage to the roots the soil would have to stay consistently wet or boggy or under standing water for a period of time.
If not some kind of borers, the oak tree could have some kind of disease. If leaves were smaller and are turning brown all over the tree, this would make me think there's a problem with the soil or the roots or a canker down low on the trunk. If it's a canker or borers there should be some kind of evidence, such as sores or holes on the trunk or the branches.
Nuttalli likes an acid soil with a pH of between 4.5 to 5.5. If the soil is too alkaline this might have caused or contributed to the problem. Soil sulfur and/or chelated iron can be applied to increase the acidity.
Too much digging around the root system of the tree can cause problems...distorted and smaller leaves. Spreading a weed & feed type lawn fertilizer around the roots can cause major problems and death of the tree as well.
You might consider having a local arborist come by to take a look at and diagnose the problem with the tree.)