PYRETHRUM HIGH POTENCY (Chrysanthemum cinerariifolium). Beautiful white daisy contains the strongest potency of natural insecticide you can grow. Pyrethrins act directly on the nervous systems of aphids, mites, leafhoppers, cabbageworms and other insects. Will not harm fish, waterfowl, plants or mammals. To make pyrethrum spray, mix 1 T of freshly ground dried flowers with 2 Qts hot water. Add a little soap and let stand. Perennial. Hardy Zones 4-9.