Insecticide activity and toxicity of the three <i>Alpinia</i> species essential oils against stored-product insects

In the pursuit of conducting a systematic investigation on the bioactivity of the family <i>Alpinia</i>, and searching for bioactive natural products to minimize the risks of synthetic pesticides, the <i>Alpinia blepharocalyx</i> K. Schum, <i>Alpinia oxyphylla</i> Miq. and <i>Alpinia zerumbet</i> × <i>A. henryi</i> ‘Red Harvest’ were selected as objects. The essential oils (EOs) of the three <i>Alpinia</i> were obtained by hydrodistillation and analyzed for chemical composition, evaluated for bioactivity toward the adults of <i>Tribolium castaneum</i>, <i>Lasioderma serricorne</i> and <i>Liposcelis bostrychophila</i>. A total of thirty-six components were identified in the extracted EOs, mainly composed of monoterpene hydrocarbons (0-91.75%) and oxygenated monoterpenes (0-57.82%). GC-MS profiling displayed perillal, ѱ-limonene, 1,8-cineole and β-pinene as major contributors to EOs area percentage but quantitative variations were observed with variability in the five EOs. The EO of <i>A. zerumbet</i> × <i>A. henryi</i> ‘Red Harvest’ fruit (EOAZHF) possessed the strongest contact toxicity against <i>T. castaneum</i> and <i>L. bostrychophila</i>, with the LD₅₀ value of 14.02 μg/adult and the LC₅₀ value of 48.64 μg/cm², respectively. While the EO of <i>A. oxyphylla</i> rhizome (EOAOR) exhibited the highest contact toxicity to <i>L. serricorne</i> (LD₅₀ = 8.06 μg/ adult). Upon repellence, all of the extracted EOs exhibited repellent activity, but the repellency gradually decreased with the decrease of concentration, and the target insects showed different sensitivities to the EOs. The results demonstrated that the EOs of the three <i>Alpinia</i> have high variability in composition and have the potential for the control of stored-product insects.