damage to white oak
I just noticed a dark patch at the base of a large white oak in my yard. When I first looked at it, it was attracting flies. When I went out a few minutes later to take pictures, several large black bee-like creatures were on it (they had 2 yellow stripes around their lower body). Then a butterfly came and started investigating it. There seem to be holes bored in the bark, and there may have been some kind of bug under the bark. Do you have any idea what this is and what we should do about it? Another white oak in our yard died a few years ago. I don't know if this is related or not.
We viewed your photos and this looks like slime flux. The wound allows entry by some form of bacteria which causes the sap in the vascular system to ferment and bubble out of the wound. Typically, it flows down the trunk for some distance and will often encourage the formation of a harmless, but unattractive, black 'sooty mold'. Insects such as wasps may be attracted to the odor.
This is usually harmless and no control is necessary. Monitor the tree for other symptoms and keep watered during dry periods.
See our website for more information http://extension.umd.edu/hgic/slime-flux-and-wetwood-trees-and-shrubs
If you notice additional symptoms or decline, contact a certified arborist regarding the health of the tree and the best way to proceed http://www.treesaregood.org/