You can't kill therm all, no matter what you do. They'll always exist in the wild and that's that. Pick them off the plants and drown them in soapy water or a half inch of kerosene (NOT GASOLINE!). Seeing the bums get poisoned and then incinerated is a great stress reliever when they've polished off half your seaberry bushes and chewed up your raspberry plants, and you don't need as much kerosene to kill 100's of beetles as you need water since they sink in k-sene.

BTW, these fixes only serve to relieve infestations in the short term, which means you need to be out there killing bugs daily... and since pheromone/floral scent traps statistically capture only 50% of the japbugs they attract, I wouldn't recommend installing one as it will make you problem much worse.