Peter - I don't know if you can get Ortho products in your area but Ortho's Bug Geta Plus will kill earwigs and slugs. I have used it and it works. Earwigs are known to favor white tipped dahlias, such as Duet, and solid white dahlias of any form. Last year I grew many colors but none that were white tipped and no solid whites. They didn't even bother AC Rainier, which is mostly white!
Good link, Susan!
