Apiol-Rich and Caryophyllene-Oxygenated Essential Oils from Amazonian Piper Species as Dual-Action Biopesticides: Broad-Spectrum and Selective Antifeedant

The increasing resistance of agricultural pests and disease-vectoring arthropods to synthetic pesticides underscores the urgent need for novel and sustainable biocidal agents. This study evaluates, for the first time, the insect antifeedant and ixodicidal activities of essential oils derived from ten Amazonian Piper species and their major constituents. Antifeedant effects were assessed against Spodoptera littoralis, Myzus persicae, and Rhopalosiphum padi, whereas ixodicidal activity was tested on Hyalomma lusitanicum. Additionally, the effects of these oils on the plant-parasitic nematode Meloidogyne javanica were investigated. Essential oils from Piper mituense (51.6% apiol) and P. sancti-felicis (76.1% apiol) exhibited the highest bioactivity, achieving more than 75% feeding inhibition across all insect species and 100% tick mortality. P. mituense consistently demonstrated greater potency, suggesting possible synergistic interactions among its minor constituents. Principal component analysis linked apiol-rich chemotypes with broad-spectrum activity. In contrast, oils rich in oxygenated caryophyllene derivatives, particularly those from P. casapiense, showed strong selective antifeedant effects against R. padi. Pure apiol displayed activity across all assays, whereas no nematicidal effects were observed. Molecular docking analyses supported these findings, indicating that apiol can interact with acetylcholinesterase in addition to its known effect on cytochrome P450 targets. Overall, these results identify complementary Piper chemotypes with promising potential as dual-purpose biopesticides for integrated pest management strategies.