My method of controlling JB isn't guaranteed to be 'the best way', it's just my way and works out for me.

Step one is Neem oil applied to plants the JB feed on every 1-2 weeks depending on amount of rain. The neem oil seems to persuade the hordes they really do not want to eat the plant, but some still will.

Step two is a daily garden walk. Sometimes I squish them, but if I notice more than one here and there I use a small bucket of soapy water and knock them into it. They do not escape, they just die. I prefer the bucket to finger squishing when there is more than one in an area as the rest seem to take flight when I try to squish them one at a time.

Step 3 are pyrethrins used sparingly and only on those plants the beetles seem to be doing the most damage to.

The good news about JB, at least in my area is they are not present until around now when things get really warm and they aren't an entire season pest either, they require control for several weeks and then 'disappear'.

They also aren't particularly bad in terms of spreading disease and they generally leave flowers and fruit alone, only damaging leaves which means I can exist with them as long as their numbers do not get too high and the plants can survive the damage.

The invasion only lasts a few weeks and they are gone. They prefer corn silks, roses, and grape vines. Most fruits and veggies can sustain 40% damage to foliage without serious harm. I just ignore them, but if you have neighbors you don't like, buy them beetle traps.
Just joking, but they do seem to attract more than they kill.
I've stayed away from sprays and chemicals for 23 years. A green bug won't drive me back.

The first step in control, and the least toxic, is a bucket of water with a bit of soap added (reduces the surface tension of the water so the buggers drown) into which the beetles are knocked. If there are too many beetles and something more toxic is needed then the Neem Oil sprays can be used. What you do is determined by how many there are, how much plant damage you can stand, and how much time and energy you want to expend on control.
Long term controls involve the grubs these adults come from and will be laying eggs in a bit that will become more beetles next year. Applying Milky Spore Disease, Bacillus popilliae, to your soil in late July / early August so the disease pathogen spores get down to where the newly hatched grubs are eating is one means of control, and there are parasitic nematodes available.
Strong, heatlhy plants growing in good, healthy soil are less susceptible to attack by insect pests so dig in now too and look closely at your soil and start doing what is necessary to balance the nutrients in the soil so good, healthy plants can grow there.

They used to devore lots of leaves on my raspberry and currant bushes at my previous home, also cherry tree leaves I think, definitely also very keen on the ivy climbing up the fence. I used a pickle jar, wide mouthed, with a smidge of water and some Borax in the bottom, and went around knocking the Japanese beetles into the jar. After getting a few beetles in the jar I would put on the lid and shake it a little bit. I liked to tell myself that before they died they quivered with fear seeing their dead comrades all around them. :-)

Eventually when the jar got disgusting, I would let it sit in the sun for a while and make sure all the bugs were dead. Then I would empty it into the trash. Viola', no chemicals in my garden, but the bugs were dead. There were a LOT of beetles, and I was mainly trying to ensure a good yellow raspberry and red currant crop. If they were just eating the ivy and black raspberries I wouldn't have minded.

I found that in the afternoon sun a lot of them were to be found on the backside of the ivy leaves, keeping cool.

Marcia

The Japanese Beetles that hit my property go for ripe nectarines. I will see four or five of them taking a bite out of one fruit, then they move onto another one and ruin that one and then onto another. They are picky and only pick the best, ripest fruit to ruin. I don't know how you people can get them into a bucket of soapy water, mine are too fast. What does work is using a tennis racquet to swat them while they are flying in for the kill, also good practice.

Thanks for the responses, I like these ideas. :) However, I often get a tad squeamish when having to kill insect directly. Is there ANY method to keeping them from touching the plants in the first place, sort of like mosquito repellent on people?....

The soapy water technique is the best. Go after them in the early morning or late evening, when they are sluggish and don't fly away. Their habit is to drop and play dead, so if you hold the bucket, or a coffee can, of soapy water under them and even try to touch them, they respond by dropping and then drown. I then leave the coffee can with the dead beetles near the garden, on a fence post. It seems the dead beetles are a repellent to other JB's (maybe some kind of smell sends a message to the others that there is danger).

The key is to get them as soon as the first scouts arrive. If you don't get the first few, they will send signals to the masses that they have found a nice home, and hordes will follow. If you capture the scouts, the message seems to be stay away.

I was thinking... has anyone tried using row covers/tarps/plastic to cover the ground next to the beds the JB are attacking? JBs need to burrow to start over again and I wonder if you covered your loose dirt if they would not be able to?

When I was a kid, I would take the beetles off the plants, pull their legs off and throw them into the air. If you're like me you'll feel bad about it later, but I'd think it would definitely keep them off the plants.

I read somewhere that garlic spray on the leaves may
prevent the beetles.

Another gross but extremely satisfying way I read was
to put these critters in a blender along with some insecticidal soap and grind them up.

Then strain the liquid and spray them on the leaves.

I don't know if anyone has tried this, but if it really
works may be worth a shot getting a used blender off ebay

I find that Concern Insect-Killing Soap solution works on the buggers. They don't die right away, but they die later. And it's supposedly safe for the environment.

IMO, you cannot ignore them and let them be, because the larvae stage is the grub that eats your grass roots. I personally have to fight this battle this year. My nieghbor put up one of those traps, so I got them. Guess he doesn't like me.

He finally went to chemicals. I have hundreds of holes in my back yard (that I don't treat because of pets . None in the front yard, that I do put weed&feed on. - hmmmmm lesson there) Off to buy some milky spore or benficial nematodes.

JB are a real problem in the coastal south east. The grubs feed on grass roots. Then the moles feed on the grubs. These 2 activities alone cause majore damage to lawns. Add to that the neighbors dog trying to track down the moles by digging up the yard. Thats 3 forms of damage just in the larval stage. I read about a product several years ago called "Milky Spore" I never used it due to the high cost, at that time I had very little to spend. Milky spore is said to be a biological agent that will cause death to it's off spring and lasts for many years in the soil. Sort of like a parasitic attack I think. The article I read was from my local extension service. I have seen the product on shelves in the stores. The article mentioned this product works best when used community wide. If you have killed off the grubs in your yard thats good. But you can still have problems with the adults flying in from the neighbors yards. So why don't I use it now? well I don't live on the coast and they are not a problem here.

Applying Milky Spore to our yard was one of the smartest things we ever did! Well worth the $$$. Follow directions, and you won't be sorry. [The moles have left, too, and in time, the spores infect the neighbors' yards.] We noticed that it becomes more effective with each year that it's in the soil.

You can make the Nuclear Polyhedris Virus by taking a few of the Japanes Beetles and whizzing them in a blender (it is probably best to not use the one in the kitchen) with enough water to liquify the wee beasties. Let that mixture steep for at least 24 hours and then strain it and mix with enough water to spray. There is no need, and it is contrary to good practice to mix this with any soap.
Milky Spore Disease, Bacillus popilliae, can be part of an overall control method, but the MSD needs to be applied at the right time of year and that is just before the eggs the parents, the Japanese Beetles, lay in about mid August. Applying MSD now may get it into your soil but will do nothing for the grubs that are pupating to become the adult beetles. Parasitic nematodes may have been of some use a few weeks ago, but since the grubs are now becoming the adult beetles they would be of little use at this time.

Thanks posyplanter - I always wondered if it was an effective product. I still have the forementioned property as rental for the moment and may return someday in the future. My sister lives in that area too and have told her about MSD but as of yet she just keeps using pesticides:(

Kimmsr - you apparently are well informed on this subject and I appreciate your input. At the moment my soil is too compacted to support such pests, so I think. In the event that I do develop problems in the future as I increase the organic matter I know who to look too for some valuable input.

Thanks!

I sprayed nematodes last spring and haven't had a problem since. They are a microscopic worm that feeds on larvae and insects. I think you could spray up to 3 times a year.

I have seen only 2 Japanese Beetles so far this year. In recent previous years they had gotten to huge yearly numbers here. I estimated that in 2003 that I trap killed 280,000 of the buggers. Last year the population was suddenly very small and with a small breeding pool, they are very low again.

I never got to see the results of Milky Spore that I put on my daughters yard in NW Indiana in 2004 as she moved away later.....$74 for 40 ounces then.

I have these everywhere right now. I do not have anything planted, just grass. There are so many that I cant even walk my dogs. I love all the suggestions, but they are all over my yard, hundreds of them. Please help

Collect into bucket of water (knocking off leaves right into bucket) and feed to the chickens. :-)

I don't have particularly that many beetles in my area despite having many plants that they love. I do crush them if I notice a plant with more than a handful but that doesn't happen much. I suspect it's mostly the birdhouses that a number of my neighbours have that are helping.

Many afternoons during beetle season I see these same birds feasting on what beetles are available and sometimes flying back to their nests with them. I'm pondering adding a couple of bird houses myself just to help some more.

I have seen only 2 JBs so far this year. !0 years ago and a little before that they were a plague here.

Trapping, killing, Milky Spore, and prayer have all helped.

I haven't seen a striped Cucumber beetle yet this year nor Colorado Potato Beetle, Squash bug, nor SVB so far...praise the Lord.