Question
Hello I have a common Holly tree in my back garden and for several weeks on certain parts of the tree there is a thick sticky resin coming from the leaves

Answer
John:
Is the resin coming from the leaf or is is possible to be dripping from a plant above? Can you send me a closeup photograph of this "resin" on the leaf? This will give me a better idea.  I have not heard of an exudate as such. Take a few closeups, pick the best.  Be sure to review your image on the computer before you send it.  It will need to be in focus to be of value.

Thanks
Steve