At the very least, kill every one that you find. Knock them into a bucket of soapy water, squish them with your foot (sometimes they fly away too fast though), do whatever it takes. Every one that you don't kill breeds more for next year. Like weed seeds and mosquitos.

Take no prisoners!

get a mayonnaise (or similar) jar. capture as many as possible in the jar and put it in the hot sun for a day or two, then throw them in the garbage (they will die)! the jar makes em easy to catch.

it's important to be able to spot the larva as well. i think we are all very familiar with the japanese beetle grub - when i find them, i pick them up and throw them onto our hot asphalt road for the birds to eat (click picture for the full article):

mk87, encourage these things to take up residence in your yard- they seem to eat Japanese beetles. Our son sent these pictures of one on his deck in N.C. Yes, that is a beetle in it's mouth.
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I tried throwing the grubs in the road, but I noticed that sometimes they are able to crawl back to the soil before a bird comes by. So now, I just squish them. I'm not taking any chances.

Remember, the grubs are small and they are near grass. If you find similar but larger grubs and they are not near grass, they are most likely the grubs of another beetle. I leave those alone; there are many native beetles that deserve a chance to live.

esh -- I never can catch them before they fly off, but I am going to try harder. Might try the jar idea though (thanks satellitehead!)...although I doubt I will be any faster that way. That maple is about 20 feet tall, so catching them on the tree itself is pretty difficult. I don't remember them being this prolific last year...of course, I've planted more things this year, so...

Also wondering if all of the recent storm tree-damage here in Macon, is bringing them out more. ???

Do martins eat Japanese beetles by any chance? We have been thinking of setting up a pole for some martin houses in the back yard...

mk87, we should make a contest of it - keep track of how many you kill. Whoever kills the most wins a prize. A prize like having fewer beetles next year! :)

As for purple martins, it does look like they eat them:

Martins, like all swallows, are aerial insectivores. They eat only flying insects, which they catch in flight. Their diet is diverse, including dragonflies, damselflies, flies, midges, mayflies, stinkbugs, leafhoppers, Japanese beetles, June bugs, butterflies, moths, grasshoppers, cicadas, bees, wasps, flying ants, and ballooning spiders. Martins are not, however, prodigious consumers of mosquitoes as is so often claimed by companies that manufacture martin housing.

Here is a link that might be useful: More on Purple martins

esh - i noticed that as well a couple of weeks ago and wouldn't have expected to see them moving so easily on the ground. scary part is, they seem to "sense" where the dirt is and head right for it. how do they do that?! i stomped them either way.

gmom - that is an amazing picture. that looks like a bumblebee? if it is, i'll tell you - they absolutely LOVE border speedwell flowers, carolina jessamine, and, more than anything, they go berserk - in a good way - for anise hyssop (be careful - it reseeds in a very prolific manner).

esh -- Hubby is not a gardener, but for some weird reason he has really gotten interested in this Japanese beetle issue. I think he really gets a charge out of killing the little suckers! LOL He went out yesterday...on his own...and bought spray and traps and has big plans to put all of it out tonight. Heck, I'm letting him go for it. I have enough to do and I think it's cute the way he's getting all into it! I think the martins are a good idea and I'm going to look into that. Not sure if it's too late to put them up this year or not, to do any good this year, but as you say, everything I do this year reduces their numbers for next year!

Satellitehead, they thought it was a bumblebee at first but then they saw it had wings like a horsefly. I looked up horsefly and found the female needs a blood meal in order to reproduce. I don't remember that the beetles have blood- I've killed a ton in the past. When we moved here thirty years ago there were thousands over the area. Over time, they have disappeared. But to help save our grass at that time, I put down Milky Spore, which seemed to help.

mk87 - be careful where your DH sprays. i've read and seen so many stories which relate the disease and death of honeybees nationwide (huge crisis right now) has been linked back to spraying of pesticides by home gardeners. i'd read elsewhere on here that it's OK to spray the leaves, but avoid spraying near the flowers, you don't want to hurt any of our friendly pollinators.

satellitehead -- I think he said he got insecticidal soap anyway...would that be OK? I disposed of the Sevin dust I had in the garage (for the reason you mentioned) and only use the Sevin spray now in dire emergencies, and then only in the evening as someone (may have been you?) on another post suggested.

i'll openly admit - i am not the expert, and probably the wrong person to ask; hopefully someone more knowledgable can chime in. i have encouraged my DW not to use pesticides/insecticides in the yard, advised her that we would find alterantive means. we haven't see any of these guys as of yet, so ... i'm keeping my fingers crossed.

they seem to attack our neighbors more than us, although i cannot fathom why they would be so picky.

satellitehead -- There are apparently a group of trees that JB's really like. In our case, it is the crape myrtles that attracted them. So maybe your neighbor just has more trees they find tasty!