What is eating my climbing hydrangea?

I planted a climbing hydrangea against the wall of my house facing the street. There is no garden here and it is coming directly out of a hole the council made for the purpose in the pavement. It has been there a year and something was eating it leaves very badly last summer and it started again this year. I can't see anything. What can it be? It is hardly snails as there is nowhere for them to hide. What can I treat it with? My wife put on some insecticide and it looked better straight away but I would prefer a bio solution. I have both a mix I have made from rhubarb leaves and pythrerum.

 

The problem is it is looking healthy now my wife but the insecticide on!

I guess I just have to wait for whatever it is to attack again ...