Patch 2.5% Ec belongs to a class of insecticides known as synthetic pyrethroids. Synthetic pyrethroids are man-made insecticides created to mimic the chemical properties of the naturally-occurring insecticide pyrethrum, which comes from the crushed petals of the Chrysanthemum flower. Synthetic pyrethroids, like Patch (lambda-cyhalothrin), are often preferred to the real thing as an active ingredient because they offer the added bonus of remaining effective for longer periods of time.