Abstract: The present invention is directed to pest-controlling compositions comprising as active ingredients one or more ?-diones, particularly ?-diketones and ?-triketones, and to the use of these compositions inter alia for preventing, eradicating, destroying, repelling or mitigating harmful, annoying or undesired pests including insects, arachnids, helminths, molluscs, protozoa and viruses. The present invention is further directed to processes of preparing ?-diones by de novo synthesis or from natural sources such as volatile oil-bearing plants from families including Alliaceae, Apiaceae, Asteraceae, Cannabinaceae, Lamiaceae, Pteridaceae, Myrtaceae, Myoporaceae, Proteaceae, Rutaceae and Zingiberaceae.