United States 
Hi, the sticky "sap" from my neighbors' oak tree is getting all over my walk and solarium (sun room). I have seen two different possible causes: infestation by some kind of insect and a bacterial infection. In either case, my question is this -- will the problem go away once all the leaves fall off this fall? I need to have my solarium pressure washed but want to wait 'til after the problem has gone away. Thanks so much.
31 Oct, 2018
Answers
Sending sympathy - we get the same thing when we park the car under the sycamores...
1 Nov, 2018
I know you don't want to hear this, but I think you have bigger problems than sticky sap on your solarium. From what I understand, aphids seem to target already stressed trees. Sounds like it could already be in a weakened state; and one big storm could send it crashing through your roof. Seldom are healthy trees attacked.
'Minor wooly-aphid infestations seldom damage healthy oaks. Continued heavy feeding on trees already stressed from drought or disease, however, may result in general weakening.'
https://homeguides.sfgate.com/can-wooly-oak-aphids-oak-trees-72108.html
2 Nov, 2018
Hope its not that, but the sycamores that drip onto D's car are actually disgustingly healthy...
2 Nov, 2018
welcome to GoY Donna.
It sounds like the oak may have an aphid[greenfly] infestation. They secrete a sticky sugary fluid from their guts called honeydew. This coats everything it lands on then a secondary fungal infection feeds on that and you get black mould.
Once the leaves drop the problem will go away until next year. The aphids will be back and you will have the same problem again. Its not practical to spray a full tree especially if its is a mature oak.
31 Oct, 2018