You are disagreeing with math. That's like disagreeing with gravity.Thank you, but I'm going to disagree on that. There are people that like that stuff, and people that don't. I don't mind using it on individual birds, but no thanks on the mass application. They have found permethrin traces in the eggs of birds who were treated with it, months after treatment. "No withdrawal period" as some one said on a permethrin related thread on here?, That's laughable. No thanks. Furthermore, wood ash has always had excellent results for us, and was recommended to me by a poultry vet recently as a very effective way to control lice. Maybe not after the fact, but certainly as a preventative or control measure.
Now, you may have a much lower risk tolerance than what has been established by testing, That's fine if you want to pedestal your opinion over those of greater expertise and experience - but your argument that measurable levels of permethrin remain in eggs months later has more to do with the ability of modern measuring devices than any issue of safety. Later I'll find the study of how long traces remain, then we can do more math.
