I have a beautiful Dogwood and for this past three or four year the leaves get devoured by a grub type creature that is brown on the top and yellow on the underneath. I find loads of them curled up on the underside of the leaves. As I garden organically I have to pick them off and hose them off. It's a constant battle. I've been trying for a long time to find out what they are, but no luck. If anyone can help I'd appreciate it.