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Diatomaceous Earth (DE) consist of the sedimentary deposits formed from the skeletal remains of a class of algae (Bacillariophyceae) that occurs in both salt and fresh water and in soil. These remains form diatomite, an almost pure silica that is ground into an abrasive dust. When the tiny razor-sharp particles come in contact with an insect, they cause many tiny abrasions, resulting in loss of body fluids. DE is the secondary ingredient in a variety of insecticides. DE being a natural product is harmless to mammals and birds and is digestible by earthworms.

DE is found to be beneficial in conjunction with grain and seed storage and as a deodorizer on fecal and other waste around barns, kennels and garbage cans. Both USDA and TDA has information on using DE.


Use as a dust to control odors and in grain storage and as an absorbent to soak up oil or other spills. On plants use as a spray mixing one to two tablespoons of DE and one tablespoon of insecticidal soap per gallon of water. Spray upward from the ground covering all stems and leaves, especially the undersides. NOTE For more information on DE consult Encyclopedia of Organic Gardening by Rodale.

DE test on fire ants as an insecticide

Will DE kill fire ants? That was a question I could not truthfully answer without doing my own testing. I had heard strong arguments both ways.

For a test I got two 1 qt. fruit jars and put one teaspoon of DE in each then went and found a healthy anthill and put heaping tablespoons of anthill with very mad ants into each jar, I put one spoon in one than the other and continued alternating until they were fiercely coming up the handle and attacking me. I was forced to stop at about six tablespoons in each then I quickly placed lids tightly on each jar then I shook each slightly to mix the DE in the soil to make sure the ants would come in contact with it.

This test was taken about 4 pm, and a check made about 9 pm showing all ants to be active and healthy, a second check was made at 9am the following morning and discovered the jar containing brand A had all dead ants and the other jar with brand B had healthy and active ants; another check was made on them about 3 pm and they where still alive, however at 8 am the next morning they to were all dead.

Now I knew that DE will kill ants but I wanted to know exactly how long it took so I decided to take the ant samples early in the morning so I could watch them all day. I did everything the same as on test #1 except I used a third jar for a check, I just put in the ants with no DE, I placed all three jars on my desk so I could watch all day. Days, went by with nothing happening, the ants were still all-alive and appeared healthy. On the 9th. day something finally happened, the ants in the check jar, the one with no DE all died. Not until the 13th. day did I notice ants starting to die in the other two jars. By the 16th. day the ants in brand A jar were finally all dead, on the 18th. day the ants in brand B were finally all dead.

Now I was really puzzled, DE prolonged their life instead of killing them. More test were definitely needed, but how? After much study I decided it must have been the difference in the moisture in the jars between the two tests. The first test was taken in the afternoon when the ant hill moisture was low and the humidity was also low while the second test was taken early in the am when the air and ant hill contained much more moisture and the moisture kept the ants from losing body fluids and some how the ants received energy or something from the DE to actually help them survive longer.

On the third test I again used three jars but all with DE. I decided to include a third brand. All samples where taken from the same mound being real careful to get all exactly the same and as low as moisture as possible. The samples were taken on a hot dry afternoon and by the 5th. hour the ants in brand A were all dead, brand B by the 9th. hour and C by the 11th. hour.

I learned that DE would kill ants in a low humidity in jars within 5 hours. But how fast would they die in only dry soil in jars? For a test I used 2 jars with equal amounts of soil from an ant mound with ants, one jar I shook as if I were mixing DE in like I did in the other DE test, the other jar I disturbed as little as possible. The ants in the disturbed jar were all dead in two and one half days. The un-disturbed ants took a day longer.

NOTE All of the jar tests were kept in the office out of direct sun light at a temperature between 72 and 82 degrees.

I needed one more test. Would DE alone kill ants in the field? I found a lone big healthy ant hill with no other close by and applied about 4 oz. of brand A and then took a stick and scratched it in real well, I did this in the afternoon when the humidity was low. The next day at noon I checked on the ant mound, and no live ants could be found and no new mounds later appeared in the area as when using some other insecticides.


All brands of DE tested do kill ants, all though some faster than others, and the method must be de-hydration because when there is high humidity there is limited affect and even beneficial effects. However if given a choice the ants definitely will stay away from D.E.


I had a 20 gal. trash can that I used to store fish food in and always had ant problems, the fire ants loved the stuff and I had heard IMPORTED fire ants were toxic to fish. I took one pint of D.E.and spread it on the soil around the trash can, this was several months ago, the D.E. has spread around and worked it's way into the soil some, this is in a green house where I raise tropical fish, the humidity is always high but the fire ants still stay away from the fish food, there hasn't been a single fire ant in fish food since the day the D.E. was applied.


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last updated:  February 10, 2004