Are you sure you are using the right mixture, as per the bottle directions? Also do you have a pump sprayer that you can purchase at any garden store, Agway or Home Depot?

If you are not controlling them Be sure to entirely soak the plant - uper and lower leaves, especially the growth tops.

Pyrethrum is milder; I doubt it will suffice.

Good Luck

I use Safer insecticidal soap. It's organic and has ethanol and fatty acids to dissolve insect's waxy skin. I used it only once on whiteflys and they were instantly gone and haven't come back for a week now. Doesn't kill beneficial ladybugs or bees. I've heard it's best not to use when direct sun is on plants so it doesn't get "burnt". I also heard that if you're using the concentrate and diluting with HARD water it doesn't work as well (can't verify this though).

This is the first time I have checked this Forum. Re: whitefly. It must have a host plant to reproduce. Do a search for "whitefly hosts" and carefully reads the lists of plant names that will appear. You are growing one or more of them in your yard and if they are removed your whitefly problem should end.

Thank you all. They seem under control now. I think I have found the host which was planted right next to them. Who knows. Iused Malathion which I didn't want to do but I wait all year for my dahlias. They won't be a good as last year I am afraid.