I did some research so I'm going to post what I found:

* First a tip - if picking them by hand, do it early in the
morning when it's cool, they will fall into your soapy water
rather than fly away.

* second, you can make a spray:

Japanese Beetle Traps don’t
really work because they tend to lure in more beetles than they
can handle. Picking them off by hand, drowning them in a jar and
getting them off the property, while satisfactory from a revenge
standpoint, is laborious at best. Simply shaking them off and
stomping on them attracts more because when killed, the female
emits a pheromone that attracts males. Hardly the desired
result.

So, is there a natural
alternative? Thankfully, the answer is yes. Double thanks
because you can make it yourself!

It’s simply a spray made from
cedar oil! Preferably Eastern Red Cedar. The principal is the
same one used when storing sweaters in a cedar chest to keep
moths away. When sprayed on the roses it keeps the beetles away
and they fly off to another garden. I know this for a fact
because I’ve tried it and boy did it work!

You can buy it from various
on-line sites but recently I found a recipe for it. Simply take
a few red cedar planks say a foot long each and put them in a
one or two gallon bucket. Pour hot water over it and let it
steep like tea for 24 hours. Cut the planks in half if needed,
but make sure they are totally immersed in the hot water.

Pour the liquid (don’t dilute
it) into the sprayer of your choice and spray the roses and the
beetles. You may have to play around with how much cedar wood
you use to get the right strength. When you have it right the
beetles will either fly away or drop off almost instantly.

* I notice the above author says to remove the drowned bugs
from the property, but another author says to leave the beetles in
the bucket near the plants that are having problems, and as they
decompose the smell will deter other beetles. It also says to use
1/2 bucket with 1/4 cup of disk soap, but that the amount of soap
isn't absolutely critical, just that using soap discourages/kills
mosquitoes that otherwise would breed in the water.

I'm getting ready for the
anticipated onslaught!!!

Hi ridgetop01 (zone 5b)(z5 CNY) thank you so much for this advice I will definitely try it. In the past I put alcohol in a glass jar & went around knocking the beetles into the jar where they died. The tricky part is getting them to fall into the jar because as soon as they become aware of you they fly off. But if you hold the jar underneath them, you can tap them & they fall in. I agree the Beetle traps lure them into your garden. Roses seem to be a favorite plant of these beetles :(

Re. the lily beetles I went around & removed them by hand (disgusting job). Not sure if this works long-term

Honestly, I've spent 4 years dealing with these disgusting bugs and their feces-covered larvae, twice a day for weeks, till I was rewarded with the beautiful lilies with minimal damage. I dug up every one of those lilies and am finished. Battling pests is too frustrating as I age. I am sticking with trouble-free perennials. I have enough frustration dealing with rodents eating my vegetables.

Bye bye lilies. You had your years making me happy and now it's time for me to relax a bit.

Had to rant.

sigh. I too had red lily beetles... they showed up last year and I thought they were a different kind of ladybug. lol! They completely ate my lilies before I even knew what was happening. When I saw them this year I tried a few different things and realized the only way to really get them was to remove them by hand and crush them! wear gloves to pick, then stomp and smoosh under foot on a hard surface like pavement. lol!

The Japanese beetles were HORRIBLE on my blackberries this year! I tried using a container of water with a squirt of dishsoap in it, held it under the leaves and easily knocked most of the beetles into the soapy water where they just don't come out. Just don't make the mistake of emptying the container before all activity has stopped, iykwim. :p

ETA: another organic option with JB is milky spore powder... apply to lawn and it kills the larvae. The problem is you have to do many applications over time and it's not cheap!