I JUST GOT THEM THIS YEAR!!!!! I'm going crazy- setting up traps, and spraying the lawn to kill the larvae. So, yes they have made it to Missouri, it's a sad year for all of us Missourians.

They're worse this year but they've been around for at least a few years. I've had more every year for the last four or five years now. They like my crape myrtles, roses, cannas, and butterfly bush.
The good news is they're starting to disappear for this year so you may not see many more until next summer.
Macguy - I haven't tried the beetle traps but I've read several times that they just attract more so you may want to read up on them before you put them out next year. If you have a large property, you can locate them away from your garden.
I think it would be nice if the conservation department would put up some industrial sized beetle traps and thin them out a little for us. I don't like using sprays which they say don't work very good anyway. It wouldn't make much sense to spray my butterfly bush unless I wanted to get rid of my butterflies too. When I first started seeing them, I handpicked them off of my plants. Early in the morning, they're sluggish and easy to knock off into a jug. I have so many now that I've given up on that. I can't get them all.
Four o'clocks are supposed to be poisonous to them. The article below talks about using using them as pest control. Japanese Beetles do sooo much damage. I think it would probably take a combination of things to get rid of them.

Here is a link that might be useful: Pest Control Plants - P Allen Smith

I think in about september I'm going to treat my lawn with milky spore. I'm also going to look into beneficial nematodes.

This so sucks!

I had them for the first time last year and they were even more plentiful this year. I have just been picking them off and drowning them. Hate, hate, hate them and their damage!

Funny about the 4 o'clocks, I was just talking about trying them next year.....now I will for sure.

I have been swarmed by the darned bugs! They have completely deleafed my plants. Everything is so ugly now. Even my cabbages are completely holey.
Bentonville. Mom in Bella Vista too.
Tried traps, work great if downwind of your property. Empty every day. Someone told me if you cut a little hole in the bag, poke a pvc pipe in it -about 1/2 " size, tape it securely with duct tape, let it hang over a bucket of soapy water, they go in, drop down and drown, I'm gonna try that next year.
In meantime, traps, soapy bucket, shake crab apple and maple saplings, and hollyhocks, roses, etc, over it and kill as many as possible.

Luck next year ya'll.

Japanese beetles in the summer of 2006 were devastating around Springfield, Missouri. No, no to the traps. In 2005 a neighbor used them and brought countless thousands of beetles to the neighborhood. In 2006 she didn't and we had a dramatically lower number. Believe it or not, the most effective control--as attested to by many older and more experienced gardeners--is to go out early in the morning and knock them into a container of soapy water. In very large gardens spraying is sometimes unavoidable. It works but must be repeated frequently.