Question
We moved into our house last winter, and when the trees got their leaves back this spring we discovered that they are producing a ton of black ick all over everything. It looks like mold, requires a power washer to remove, and reappears within a day. It's all over the deck, the deck furniture, the playground, everything. The trees all have black spots all over the leaves as well. The whole yard is full of these trees (there are like 9 of them) so I'm really hoping there's a solution other than "pull out all the trees and start over". I think the trees were original to the house, which would put them at about 15 years old. According to a neighbor, a lot of the pin oaks on the street were taken out by their owners a whole back because of some fungus, but she didn't know the specifics and u haven't seen any other neighbors to ask yet.

Answer
It is not the trees but an insect sucking the plant juices. Sounds like either aphids or a scale insect--both insects will suck the plant juices from the plant and secrete a substance called honeydew which is high in sugar content and sticky. A sooty mold will grow on this sugar making the black. Control the scales and aphids and the honeydew will go away. Treat the tree with an insecticide called Bayer Advanced Tree and Shrub Insect Control. This is applied to the soil around the tree and the roots will carry the insecticide to the leaves and stems and when the insects suck the plant juices they are killed. It will take a couple of weeks for the insecticide to get to the top leaves depending on the tree size. Here is a web link to this product check with your local nursery type for this product. Apply it early this next spring as the leaves are budding out and it will get into the system faster. It will control the insects for the whole season.

http://www.bayeradvanced.com/insects-pests/products/12-month-tree-shrub-insect-c