Diatomaceous Earth is what is left of some wee sea critters from eons ago, a shell like silica stuff. The food grade is not processed much so the sharp edges remain to cut into the exoskeleton of some insects. What you found is the right stuff and the package it comes in, usually and what I have seen, is a shaker to apply of. A light dusting on and around the plants you want to protect, reapplied after a rain, is all that is needed. This needs to be reapplied after a rain, or after you water the garden, because the DE will absorb water and soften. Some people report that after drying the DE is just as effective as it was before getting wet. I've not seen that.

Agree with kimmsr, after any wetting DE needs to be reapplied. It also is a non-target killer and good bugs will die too, so apply judiciously as well as putting out traps and repellents.

Dan

I'll share my experiences with the other aspect of DE. I've applied it wet, with a sticker. You can add a bit of soap or horticultural oil. DE doesn't dissolve in water or soften. The additives might, though. I've seen some products with quite a percentage of ingredients other than DE.

Much of the DE will sink to the bottom so you'd have to keep the sprayer agitated. If the screen in your sprayer is too small, it won't work with DE. It simply does not dissolve. It DOES lose some of its physical aspects when wet, but once dry, it's the same stuff. Outside, an irrigation cycle or rainfall will cause an application of DE to settle into the soil or nooks and crannies, however.

There is much information about how to make it spray-able . It's been used that way for generations and for a wide range of applications ( agriculture, orchards, livestock, poultry, etc.).

All that being said, I don't use DE outside in the landscaping or garden areas any more at all for the reasons that Dan mentioned. Too many beneficials out there that can be affected by DE.

If you are trying to protect seedling flats or containerized plants, that would be different. I'd be overrun with fire ants in my containerized plants and earwigs and sowbugs in the seedling flats if I didn't. DE can be sprinkled on top OR you can mix it into the potting mix prior to planting. All of my bonsai mix contains DE.