Assessment of Contact Toxicity and Repellent Effects of Essential Oils from Piper Plants Piper yunnanense and Piper boehmeriifolium against Three Stored‐Product Insects

Abstract

Essential oils (EOs) of plant origin have been highly recommended to combating insects. To make the fullest use of natural resources, essential oils of different parts from Piper yunnanense (the whole part, PYW; fruits, PYF; leaves, PYL) and Piper boehmeriifolium (leaves, PBL) were extracted by steam distillation method in the present study. Gas chromatography‐mass spectrometry (GC‐MS) characterization revealed bicyclogermacrene (PYW), γ‐muurolene (PYF), δ‐cadinene (PYL) and methyl 4,7,10,13,16,19‐docosahexaenoate (PBL) as the principal compound of each essential oil. Sesquiterpene hydrocarbons were also recognized as the richest class accounting for 56.30% ‐ 94.9% of the total oil. Three storage pests, Tribolium castaneum, Lasioderma serricorne and Liposceis bostrychophila, were exposed to different concentrations of EOs to determine their insecticidal effects. All tested samples performed modest contact toxicity, among which the most substantial effects were observed in PYF EOs against T. castaneum (35.84 μg/adult), PBL EOs against L. serricorne (15.76 μg/adult) and PYW EOs against L. bostrychophila (57.70 μg/cm2). Essential oils of PYF at 78.63 nL/cm2 demonstrated to have a remarkable repellence against T. castaneum at 2h and 4h post‐exposure. The investigations indicate diverse variations in the chemical profiles and insecticidal efficacies of Piper EOs, providing more experimental evidence for the use of plants.