I recently Googled the beetle and any natural preds it might have. There is a wasp that buries itself in the ground and scientists say that although it's not a "cure" of course...it could lead to a better future fight against these critters.
They place their eggs on the beetle and while doing so..if I remember correctly, stab the beetle...it falls to the ground where it dies..eventually. So..the notion is to attract as many of these wasps as possible to your yard. They claim they don't sting. Suggestions on plants that will do this are: peonies and forsythia..other suggestions are also mentioned, the old standards of knocking them off in to water of course.
Just thought if anyone wanted to look it up...I'm in a hurry here this morning...later today I will try and find the link and post it here....sorry..busy..busy!