Question
I am an American living in Germany, my wife and I recently bought a house with a large and (I assume) old Lilac bush in the yard. I don't know the age of it but the trunk of our Lilac is approx. 10-12 in diameter at the base. The climate here is simular to that of the Portland Ore. area. Lots of rain, realativly cool.  We have 2 problems; 1) The leaves are turning brown and wilting and 2) We have large hornets that are eating the bark off of the smaller branches. Are the hornets causing the leaves to wilt? If so, how can we get rid of them? If not what is causing it and what can I do to fix the problem? One way or the other I would be a LOT happier if the hornets went someplace else for dinner.
Thx...

Answer
Scot,
The wasps are causing this damage by girdling the branches, removing the outer bark and cambium layer of the branches. This cuts off the nutrient flow to the leaves, causing them to wilt.
I would recommend treating the plant with orthene or if you can get it, dursban, or if the wasps are there, use sevin (Carbaryl). These materials will control the wasps.
Fertilize the plant well to spark new growth this fall and again in the spring.
Good luck.
Ed Gulliksen