I have a healthy wisteria that is being eaten by something. It started eating the leaves at the bottom of the plant and within a week it has know worked it's way up to the top. It seems to be eating the leaves closest to the trunk all the way up. I assume then it is some bug going up and down the plant by climbing the trunk. The leaves look like swiss cheese and then they shrivel and die. Some leaves are also appearing have their chlorophyll taken out in spots. I cannot find any bugs, but there are tiny little hard black "droppings?" left on the leaves. They are very small. This is going very quickly and I think I might lose the plant. Any ideas? I have attached a photo.