I did a search and found that 20 Mule Team Borax--widely available--is used to kill fleas and other pests in various areas including carpeted surfaces. The manufacturer says that it is 99.5% percent borax. Some of you may not want to use this for treating carpet since it is not 100% boric acid, but it has been used numerous times. I just bought some today, and I think I'll give it a go. Any thoughts?
Here is a message thread discussing "boric acid v. 20 Mule Team borax": http://forums.gardenweb.com/forums/load/ipm/msg0622204413443.html Steve
