I bought it at a local garden center. I wanted to apply it around plants to repel slugs. You have to reapply it after a rain and I always forgot to do that, but I think it does work if used as directed.

How would it repel Japanese Beetles? They are flying insects and I don't know how DE would work with them.

I've called local garden centers and feed stores, but the closest I've come so far is the swimming pool grade of DE, the kind that's used for filters. No one in this area seems to have heard of it!

While I wanted it specifically for fleas, I was thinking that it might also be useful for some kinds of beetles, as it works by scratching the hard shell of certain insects and causing them to dry out. It doesn't so much "repel" them as, well, kill them. I've also read that it's effective on SOFT-bodied insects- like the slugs you used it for- though luckily it doesn't harm earthworms. I thought perhaps it could be dusted on plants- maybe after a rain so it would adhere?- and beetles would be scratched as they walked over it. (I'm sure it could also kill some beneficial insects, though, and if that's the case I'd be very hesitant to use it in that manner......)

I found it at my local Lowe's that opened this past spring -
it did help a lot with my hostas, even though I didn't get to applying it late after the foliage was already well established..
I'll definitely apply it earlier as the young shoots come up, next spring.

I didn't think to check Lowe's- will do! I stopped at a local feed store this morning and found they carry "Insecto" at $4.80 a lb. It's made of "silicon derived from diatomaceous earth and human food-grade attractants (?)" I don't know why I would need to attract insects- I want them to go away!- but as a last resort it may do. The brochure mentions that it does kill ladybugs though, not something I'd purposely do.

I used DE from the pool supply store this summer. Someone on Gardenweb warned me afterwards that the pool grade DE has something in it that should not be inhaled. Honestly, I would avoid inhaling any fine powder!

It does work to deter Japanese beetles. I dusted my raspberry plants and green beans with it, either in the morning, while the plants were still wet with dew, or after a misting with the hose.
I made something like a big salt shaker by drilling holes in the lid of a peanut butter jar, filling the jar with DE, and shaking over the plants. There's almost always some light breeze, and I stand so the DE drifts away from me.

I doubt DE will scratch the beetles deeply enough to bother them. Rather, I think it gets into their joints or their mouthparts to cause trouble or discomfort. I haven't found a bunch of dead beetles under the treated plants, just not nearly as many on the plants as usual. However, it may be that the DE kills the first few beetles which heads off the orgy swarm later.

Alex

From what I understand, the pool grade is not effective for insect control (or at least not AS effective as garden grade), so it's interesting to hear that you had some success with it. I like the homemade shaker idea! I believe pool grade has been heated to a high degree, resulting in an entirely different product. I think it's not as sharp- the heating sort of melts the diatoms so they congeal into larger and rounder shapes? There also is a food grade, which supposedly is free of the contaminants that the other grades might contain, and it can be safely dusted on pets, as well as added to their food food to kill internal parasites. None of the grades are toxic, but I agree it makes good sense to not breathe in any sort of fine powder! ;-)