Pest-controlling compositions include one or more β-diones, particularly β-diketones and β-triketones, and are used inter alia for preventing, eradicating, destroying, repelling or mitigating harmful, annoying or undesired pests including insects, arachnids, helminths, molluscs, protozoa and viruses. β-diones can be prepared 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.