Yes DE works, but it has to contact the ants and moisture allows the ants to survive so it does not work in rain or after a rain and it washes away or into the soil.
I did some research for pesticide free treatments. Found a texas site that linked to a PDF with lots of studies for both home remedies/ non pesticides and pesticides. A few studies looked at insecticdal soaps...the best acting included 2% of orange oil.
However the highest kill rate (100%) came from solutions of water mixed either with Murphy's Oil Soap (1/2 to 1/2 to it was expensive), or concentrated cold pressed orange oil (6oz to a gallon). A review on
Amazon said the user mixed 1/2 cup to three gallons of water in a five gallon bucket.
I am having a major infestation, so I just ordered 2 bottles for myself.
Amazon link to reviews that discuss using orange oil for ants, as well as for other purposes:
http://www.amazon.com/Natures-Wisdo...rtBy=bySubmissionDateDescending#R7MMEG7CPK1R9
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Link to Texas research PDF:
http://fireant.tamu.edu/research/projects/pdf/urbanipmhandbook2007edited.pdf
Page 118.
Evaluation of Soaps and Oils, Murphy’s Oil Soap, QRD400, Canadian Petroleum Products Formulations Lawn 1 and 2
Bastiaan M. Drees and Bill Summerlin
Texas Cooperative Extension, Texas A&M University System, College Station, TX
Page 141.
Insecticidal Soap and Orange Oil Toxicity to Red Imported Fire Ant Workers: Development of a “Home Remedy” Recipe for Use as an Ant Mound Drench Treatment
Bastiaan M. Drees and Bill Summerlin
Texas Cooperative Extension, Texas A&M University System, College Station, TX