As near as I can tell, Milky spore (Bacillus popilliae) does not infect Asiatic garden beetles. Of your choice, Merit would be the best. It is very good a controling many beetles including scarabs, which the Asiatic beetle is one of.

Bob thanks for the reply. When I research Merit I see two varieties "Merit .5G"

(http://www.domyownpestcontrol.com/merit-granules-p-301.html)

and "Merit 2.5G"

(http://cgi.ebay.com/MERIT-2-5G-Ornamental-Systemic-Insecticide-Granules-4lb_W0QQitemZ7724288393QQcmdZViewItem)

which I assume is just the % of active chemical but the directions almost seem to mean they are for different purposes.

Do you know what would be best suited for a perennial garden?

I took a look at the pesticide labels. You are right about the main difference being the concentration (%) of the active ingredient in each product. You can find information on most pesticides at the link below. Just type in the product name, select the formulation, then you can look at the specimen label or Material Safety Data Sheet (MSDS).

They are both labelled for ornamentals which would include your perennials. Merit .5G is labelled for Asiatic garden beetle and can be applied to turf and ornamentals. Merit 2.5G is only labelled for ornamentals but does not list Asiatic garden beetle under pests controlled. Would it kill this insect? Undoubtedly, but any time you stray from the product label, you do so at your own risk. If there is any damage that occurs from a product, their liability ends as soon as you fail to follow the directions.

Merit .5G has less active ingredient which makes it safer to handle and usually more expensive since you would have to use 5 times as much to get the same amount of pesticide.

Here is a link that might be useful: CDMS Labels database

Merit is a very broad spectrum and potent poison that will kill most all of the soil life you have, although there are some of the target population that are immune to this product. Since this is such a broad spectrum poison it should only be considered for use as an absolute last resort poison.
Milky Spore Disease, Bacillus popilliae, is a specific control for members of the scarab beetle family and only affects them at certain, early stages in their life and does not adversly affect the health of any other insect as Merit does.
A start to growing plants that are not affected by insect pests as much as yours are is to contact your local office of the University of Connecticut USDA Cooperative Extension Service about a good, reliable soil test and then dig in with these simple soil tests to see what you have and what you need to do to get there;
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer you soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

Plants growing in a good, healthy soil are less susceptible to insect pests and diseases.

Here is a link that might be useful: UCONN CES

If you use merit as a pre season treatment then be sure to water in well for the next several weeks. this will insure spreading the chemical systemically through out the plant.
As for Milky Spore it will kill the grubs but takes several years to build up in the soil to high level. Reamber that each beetle may/will travle up to 1.5 miles to land on your property

Beneficial nematodes are a better alternative, without the environmental impacts, but effective in cooler soils. They will target all beetle grubs, unlike Milky Spore.

csilkman, I do not know.
But at this site there is useful information about the product.

Some misinformation on the web site linked above.
Milky Spore Disease is a naturally occurring bacterium, it was not "designed" by anyone to control a specific member of this very large beetle family. The bacterium, "Bacillus popilleae", causes Milky Spore Disease in the larva, grubs, that ingest the spores. This is a passive method of control and depends on the larva, grub, moving about and ingesting the spores that cause the disease.
While this means of control can well work long term it is not a quick fix like a broad spectrum poison would be, but it creates fewer environmental problems.

Here is a link that might be useful: About Milky Spore Disease

Take it from someone who fell for the milky spore marketing and spent over $1000 on it, applied it for three seasons and then STILL battled grubs every year. I could write a book on why this stuff should never be bothered with.

Does it kill Japanese beetle grubs? Sure it does -- but only after multiple seasons of treatments when there were enough grubs in the lawn to effectively spread it throughout the soil -- and it ONLY kills Japanese beetle grubs.

Turns out our bigger grub problem was masked chafer grubs, and they are unaffected by milky spore. Most if not all areas that battle Japanese beetle grubs also have the masked chafers, rendering the MS a complete waste of time and money.

As for MS controlling the beetles, as the advertising boasts -- give me a break. Do all your neighbors within a five mile radius go to the trouble of treating with milky spore? Because if they don't, let's remember something very important about beetles: THEY CAN FLY.

There is absolutely no justification for using milky spore. If you want to go an all-natural route, go with beneficial nematodes. I have used those also, but the application process is very difficult. Essentially, the soil must be wet to a depth of eight inches and you must apply the nematodes at night because sunlight kills them. So imagine me watering the lawn on a day before rain was forecasted, and then going out at night with a flash light, watering nematodes through a hose-end sprayer onto the lawn in a thunderstorm.

We used Merit after that.

Mulch, part of your problem is in not understanding how these different things are best used. It's much easier to use Merit, after all!

You've certainly made using beneficial nematodes a whole lot harder than it needs to be, lol. The soil needs to be moist, not soggy and applying them at night is not necessary......a cloudy day is fine, or at dusk.

Milky Spore is used to control the grub population, not the adults. Once inoculated properly into an appropriate soil, MS can continue to spread and infect JB grubs for many years.

It is a very effective tool in a multi-faceted integrated pest management program.