Ants have made their home in one of my garden beds. This became obvious yesterday as I cleared the bed to prepare it for fall planting. Suddenly they were everywhere, upset that I had destroyed their home. I had read that diatomaceous earth (DE) could be used to kill ants and I had purchased a bag to have on hand just in case. I can now assure you that it works.
Diatomaceous earth is a fine white powder that looks like flour. It is made of the skeletons of tiny marine creatures called diatoms. Under a microscope the powder actually has sharp edges which are abrasive to the exoskeletons of insects such as ants, earwigs, roaches and silverfish. When the insects crawl over it, the powder scratches off the outer waxy coating causing the insects to dehydrate and die.
It is not a bait, so the insects will not be drawn to it. This means that to be effective, it must be placed where the insects will crawl over it. Diatomaceous earth must also be dry to be effective. Once it becomes damp, the tiny pieces won't coat the insect and it won't kill them, so it must be reapplied often to work.
My ants were making a trail along the 2 x 6 of my raised bed so I spread the powder along the top of the board, and also spread it on the sides to be sure the ants had no way of avoiding it.
Because I had never used it before, I stayed and watched what happened to see if it was working. Sure enough, the ants would crawl into it then gradually I started seeing ants fall off the wood and die. After about 30 minutes, what had been a army of ants was now a few survivors. It really worked. I'm a believer now.
The good thing about diatomaceous earth is that it is non-toxic to animals and humans. But it is important to know that there are two type of DE. One is food grade which can actually be eaten by people and is placed in grain bins to keep the insects out. This is the type you want to use in the garden. The other type is pool grade which is used in some types of pool filters. This is not the type you want to use in the garden. Although food grade DE is safe to eat, it is not safe to inhale it and DE can be an eye irritant so it is best to use a mask and goggles when applying it.
I used the DE yesterday and when I went out to the garden this morning there were no ants to be found. That's one small victory for this urban gardener!