Read and follow label directions for any pesticide. Horticultural oil can damage to plants if directions are not followed carefully. Yellow and blue sticky traps advertised in garden catalogs won't catch enough of the pests to make any difference. By the time these tiny insects are found on the sticky traps, they will already be inside flowers or foliage buds, where it is difficult to apply an external treatment that will affect them. By midsummer, many of the beneficial insects will help control the thrips, but by then the damage to your flowers has already been done.
Prevention is usually a better option, when it is possible.
Co. Willoughby, OH 44094-5992. Pacific Northwest Insect Control Handbooks . Extension Services of Oregon State University. Corvallis, OR 97331-0817. Ortho Problem Solver . 1989.