Last spring my wife and I planted 6 young Rhododendron (about 3' in diameter x 2' tall). As far as growth, they flourished, increasing in size by a good 20 or 30 percent. However, as the summer dragged on, something appeared to be eating the leaves. By the fall, some of the branches had died completely. For first year plants they wintered relatively well, yellowing a bit but making it through the cold and snow (I live in PA). Now that it's spring again, they have come back to full green, but they still seem to be under attack.

I am somewhat of a novice gardener, so I was hoping someone could provide a diagnosis and some advice on how to deal with the pest. Also, if I have left any critical details out please let me know and I will do my best to provide any additional information. Hopefully the image will help with any questions.

Many Thanks!