Mature Oak or Rhododendron dripping sap?

[RoyT]

Parked my car under a friends mature oak tree on Saturday and came back to find the car spotted with sap - I did not think such as oak trees dropped sap? Also nearby was a mature Rhododendron - could the sap have blown from this rather than the oak?
Be it one tree or the other is the sap coming from the tree itself or insects in it and regardless of the source is this going to recur all the time or is it just a summer thing?
Thanks for any thoughts.
Roy

[Jess]

Hi Roy

Sounds like it is probably honeydew. A sticky substance excreted by aphids. Firstly see if you can spot any. Normally on the underside of the leaves or around the leaf stem. Secondly it will be seasonal if it is aphids. Not a lot you can do about it unless you want to chop the tree down!