I'm not familiar with the sponge, have only seen the granules and powder types. From my research, the powder is the best way to go. The granules, while "easier" since you put it down with a spreader, take (I believe) 2 applications each year for 3 years, while the powder, if properly put down, is a single application and done. The powder is more expensive initially, but the price of the granules over 3 years ends up being quite a bit more $.

Whoops, looks like I was confusing my beneficial nematodes with milky spore. You are right the 2 main methods of application are powder and granule, and you are also right (ended up spending a couple hours Googling) that the powder seems to be the most recommended and effective. I ended up grabbing a 2.5lb bag on Amazon for ~$70 with shipping. This is overkill for my lawn (I don't care much about the actual japanese beetle issue, since it would require everyone in our area to use the powder, rather just that my lawn itself is mostly free of munching grubs.

The only thing I find odd is the application method for the powder. Both the applicator (which I hear is a piece of junk and not worth the money) and the normal method of 1tsp or so per 4 feet just seems kind of dumb. Reason being you end up having very concentrated dots all over your lawn but total coverage of only a fraction of the total percentage. Has anyone thought to kind of shake the teaspoon in the area to better cover rather than very concentrated dots?

The only thing I can reason is until many grubs are killed by the milky spore it requires very high initial concentrations of the spore in the grub to turn deadly...but that doesn't jive with my knowledge of how this treatment works...

Thanks again for the helpful reply!

Not sure, I put it down the way they wanted it, over about 9,000 sq. ft. Maybe more of a chance for a grub to ingest spores in a concentrated area? For the product to work well, you need to have plenty of grubs, and at the right time of year when they're feeding. Plus, when it rains into the soil, it will still disperse a bit, the recommended method may have been tested to provide an even coverage once rained in.

Just guessing.

"but my plan is to convince my neighbor who's lawn is shared with us to allow me to apply it to her lawn just in case the grubs migrate from her's to mine"

Good idea, the more, the merrier from what I've read, but if she disagrees, as long as you have the proper coverage in your yard, any migrating grubs will die prior to destroying your lawn. Also, beetles can fly several miles, and will fly into your lawn and lay their eggs...once the grubs hatch and begin feeding, they ingest the spore and die, again, prior to causing damage.

So I ended up doing the application tonight. We've had almost no rain and there is none in the forecast for the next week and it's the perfect time of year for this application.

I stripped down to my shorts and wore flip-flops, put on some gloves and wore a dust-mask. I figure the main danger (even though non-toxic supposedly) is inhalation but other than that I wanted to be able to hose off and contaminate the least amount of clothing (I have a wife and 2 kids, one is a 2-month old). I wear glasses but didn't put on sealed goggles, so made sure to stay upwind at all times. Again probably overkill but better safe....

Grabbed an old plastic teaspoon measuring spoon and a 3 1/2ft section of gutter to use as a guide. I put the teaspoons of powder evenly spaced out with the guide and then hand-watered the lawn focusing on the white spots until they were gone. You get a bit of loss when the water first hits the spots and it goes into the air but I'm assuming it's a very small percentage.

All in all it was an easy but somewhat tedious job. I had read a lot of bad things about the overpriced and junk applicator so the hand method was definitely more back-breaking and time-consuming. But it was free and worked well.

Thanks for everyone's help and hopefully I can report back next season and find some milky grubs underneath the soil.