The good news is that grubs usually don't hit twice in a row, but I can understand your concern. In your area (nawth of the Mason-Dixon line), milky spore seems to work pretty well. Start applying now and hit it every six months or so for a couple years to get it into your soil. Milky spore is a disease that kills the grubs, but it doesn't affect people, pets, birds, reptiles, or fish.

Milky Spore Disease, Bacillus popilliae, is a natural occuring diseases pathogen that only affects certain species of beetle larva, providing they ingest the spores and after the disease develops in the beetle larva and kills the that larva the spores are put back into your soil to later infect another beetle larva at a later time. A self perpetuating control measure.
However think of this a s one means of control and keep in mind that the Japanese Beetles may well have come into your garden from somewhere else, not just your yard. A far better control measure is to get your soil built into a good, healthy soil that grows strong, healthy plants that are not atractive to these destructive insects.

I just dont see the beetles staying away from my plants which are healthy and vigorous? Ducks work for food. I use a movable pen with several ducks in it. Every day moving the length of the pen. They drill down and eat the grubs, eat some vegetation , add fertilizer to the soil, and make a mess. The mess will disappear as the grass comes back, not long.

How about predatory nematodes?

They are supposed to destroy grubs and even root knot nematodes but not plants. I think you have to apply them at the right time of year. They come in sponges which you squeeze out in water which you spread over an area. They come in different types which patrol different depths of soil and you can get a mix of the types. They cost about $20 to cover about 2000 square feet. I think they are typically applied in the spring and/or fall.

I think Milky Spore takes several years to become effective.

I think though that the Japanese Beetle problem is not primarily with those that grow in your soil but EVERYONE's soil. You can do your part to kill them in your yard, but you might not notice a significant reduction in Japanese Beetles in your garden.

The nematodes are supposed to kill other grubs that eat your roots and mature into pests. For Japanese Beetles they can be an interim measure until the Milky Spore kicks in.

From what I hear, the best think you can do for Japanese Beetles is to talk you neighbor into setting out Japanese Beetle traps. ;) You DON'T want the traps anywhere near your garden as they attract the beetles from everywhere.

I've also heard that Japanese Beetles love to eat Four OÂclocks for dinner, but that when they do, they do not live to have dessert. I wouldn't plant them near my garden though.

NOTE: I've never tried any of this. I put out nematodes after preparing my soil last year, but I've only been gardening for a year so I have no way to know if they were effective. This is just what I've learned by researching on the 'net.

Hope that helps.

--- Mike R. Prevost

Here is a link that might be useful: Beneficial Nematodes Link

Because Milky Spore Disease is passive, the grubs have to ingest it, how quickly it works and how effective it is depends on how many beetle grubs do ingest the spores but the more of those larva that die from MSD means many more spores in your soil that could infect more larva.
It is very true that most of the Japnaese Beetles you see in your garden most likely do come from elsewhere and since each female lays many eggs that hatch into larva something must happen to many of those larve between late August, when they hatch and late May when they emerge as adult beetles, like they get eaten by many predators.
Are Four O'Clocks really poisonous to the Adult Beetles? Something I doubt since I have seen them on my Four O'Clocks with no apparent harm except when I plunk them in a bucket of soapy water.
The single best way to control these pests is to get your soil into good condition, a good, healthy, well balanced soil so the plants growing there are strong and healthy and unattractive to these pests.

Hi glorysbrite...I'm afraid I have never found a very good organic way to rid my yard and gardens of JB's. I hand pick everyday while the JB's are around...and also put out traps in the yard to catch them. Your yard...and the surrounding area(yards)will only produce x amount of beetles each year. The more you can hand pick... and catch in traps will mean that there are less females to lay eggs for next year. Some have said not to put traps in your yard...but it's another example of voodoo and witchcraft...:-) Franklin

Those Japanese Beetle "traps" wee originally designed and meant to aid in population counts of Japanese Beetles at the end of World War Two when they were found to be present inpest numbers. What is in the "traps" is a female pheromone that draws males who release a pheromone that draws females, and on ad infinitim (or may ad nauseum) but they are not a means of controlling the population of the Japanese Beetles, simply a way to draw more into your yard. The best place is in the yard of someone else so the beetles are attracted there away from your yard.

Hi kimmsr...perhaps I'm alittle slow and dense with some things...but the last I knew it takes male and female to furthur the JB species. The more you catch either by hand or with traps the fewer you will have the next year. One does not need to be too bright to figure that out. Franklin

The traps I've seen were made from a 5-gallon bucket filled with tap water and a light bulb hanging over the top (carefully). One trapper reported getting 15 pounds of bugs per night in the spring.

And the bodies are incredibly compostable (highly green). Dump the bucket into your pile and cover with leaves to keep the smell down.

I have chipmunks in my yard, and birds and squirrels that we feed. I also have lots of grubs, How do I get rid of the grubs without harming the wildlife?

Have you seen this product? It's made from Neem oil... and organic. I haven't used it, but have seen it for sale places.
"Bonide Organic Grub Beater Insecticide, RTU, 32 oz
Rid your garden and landscaping of grubs and other damaging insects with Bonide Organic Grub Beater Insecticide. Not only do grubs eat the roots of your grass, but grub predators, such as moles, can do considerable damage to your lawn. By disrupting the delicate hormonal balance of the grub and other insects such as Chinch bugs, Sod Webworms, Billbugs, and Mole Crickets, this organic botanical insecticide eliminates these insects before they can molt to the next life stage. In addition to being an insecticide, Grub Beater suppresses the desire of some insects to feed and also repels many insects in areas that have been sprayed."
It treats 2,000 to 4,000 square feet.

Here is a link that might be useful: Bonide Organic Grub Beater Insecticide RTU

Beneficial Nemetodes are the way to go.

Beneficial Nematodes - Organic Insect Control
Beneficial nematodes are underground pest hunters that control over 250 different species of insects that spend some part of their lives underground. They are a very efficient organic insect control method and kill most insects before they become adults. This includes lots of common lawn and garden pests such as grubs, fleas, mole crickets, japanese beetles and weevils.

Beneficial Nematodes - Just what are they?

The beneficial nematode is a small microsopic worm that lives below the soil. The picture seen here is of a juvenile nematode called a scarp. It is generally clear or white in color and has no segments like earthworms do. There are over 20,000 different kinds of nematodes that live in the soil and a small handful of dirt will generally contain thousands of them. Nematodes are considered parasites and can affect a number of different plants and animals. Some species of nematodes are considered pests, but these are not the same species of beneficial nematodes used to control insects.

We recommend that a combination of beneficial nematodes be applied for organic insect control (Steinernema and Heterorhabditis), these are actually two different strains of beneficial nematodes which are parasites to other insects and spend their lives hunting and killing them. These nematodes will not control or kill other types of nematodes already in the soil.

How effective are nematodes as natural predators?
When a beneficial nematode attacks an insect larvae or grub it enters the body of its host. Generally within 48 hours that host insect will either die, be physically altered or unable to produce. The Steinernema and Heterorhabditis strains of nematode carry a bacteria that generally kills its host insect in quick fashion. The beneficial nematode then moves onto another host.

What sort of conditions does it require?
Beneficial nematodes live in almost any soil, but they prefer moist soil

Japanese beetles aren't active at night. So maybe those bucket-lightbulb traps are trapping something else, for example junebugs?