United Kingdom 
My Victoria plum tree is heaving with wasps. It seems to be secreting some sort of substance that is attracting them. They are all over the ground surrounding the tree as well. I have 4 dogs and a cat that are constantly getting stung. HELP! What can I do? The underside of the leaves are covered in greenfly also.
9 Aug, 2011
Answers
The only permanent solution is to remove the tree :-(
This is what we had to do with our very large cherry tree for exactly the same reason. Wasp stings between your toes when wearing sandals is not pleasant.
9 Aug, 2011
Are the fruits still on the tree? Have you checked you don't have a wasps' nest either in the tree or somewhere nearby?
9 Aug, 2011