An insecticide formulation comprising i) a naturally occurring pyrethrin (e.g. pyrethrins I and II, jasmolin I and II and cinerin I and II) and ii) an unsaturated fatty acid or fatty acid mixture containing an average of from 16 to 24 carbon atoms (C16-C24) and/or their alkali metal salts wherein the unsaturated fatty acids are derived from natural sources and wherein the ratio of the weight of unsaturated fatty acid and/or alkali metal salt thereof to the weight of natural pyrethrin is from 3:1 to 20:1. Preferably, the unsaturated acid is a mixture of unsaturated acids. Preferably, the formulation has a pH below 7, most preferably, between 3.5 and 7. Preferably, the ratio of fatty acid(s) and/or specified derivatives to pyrethrin is from 3:1 to 10:1. Preferably, the unsaturated fatty acids are unsaturated linear acids. Most preferably, the fatty acid composition comprises oleic acid and linoleic acid.L'invention concerne des formulations insecticides comportant des mélanges de pyréthrines d'origine naturelle et d'acides gras insaturés en C16 à C24 qui augmentent la puissance de la pyréthrine d'origine naturelle.
