I can wash my car and the next t is covered with fine droplets of some kind from my oak trees. I don't think it's sap because it washes off. Do they drip water or is it some sort of sap? My driveway doesn't hold seal coat and I can see why.
Ramsey County Minnesota
The culprit may be an insect excreting honeydew as a waste product. Honeydew is the sugars and other waste products that pass through the insects' bodies undigested. Aphids or scale insects are the insects that usually cause this problems on oaks. Aphids are small pear-shaped, soft-bodied insects with two protruding tailpipes at the end of their abdomen called cornicles. A jet of water from a hose with typically remove the aphid from the tree. Aphid problems are managed by heavy rain or water from a hose, or their natural enemies and diseases. Because of their high reproductive rate and their lack of defenses, aphids are used as a food source by many other insects.http://www.extension.umn.edu/garden/insects/find/aphids-on-deciduous-trees-and-shrubs/
Can the tree be so covered with aphids that they can coat an entire Ford Explorer in one night and the car is not directly under the trees?
Yes. It happen in my yard a few years ago. Look for scales also. http://www.extension.umn.edu/garden/insects/find/scales/