Sadly this is an ever growing problem here in CO and we have so many working on solutions. Over the past 9 years, Colorado Department of Agriculture has focused its Japanese beetle prevention. There is much advice out there but not many sound reliable answers. they wouldn't survive in a natural Colorado landscape as they need 10" of water below the ground to survive and irrigation makes this possible here. Protecting bees means there are safer ways to deal with them, and it sounds like you've used many already. Milky spore in the ground in the spring may help eliminate the grubs in the ground and lastly here are
some scents they hate; wintergreen, gaultheria oil, teaberry oil, peppermint oil, neem oil, wormwood oil, juniper berry oil, chives, and garlic.otherwise we have no simple and clear solution as of yet. but here is a fact sheet which may help!
Regards
https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/#:~:text=Adults%20are%20best%20controlled%20by,or%20by%20insect%20parasitic%20nematodes.