Chemical composition and bioactivity of essential oils from Piper nigrum L. and Piper retrofractum Vahl. against Callosobruchus maculatus (F.)

Plants containing substances with insecticidal properties can be used for pest control. Essential oils of Piper nigrum L. and Piper retrofractum Vah. from dried seeds and fresh leaves extracted by hydrodistillation was determined using Gas Chromatography-Mass Spectrometry (GC-MS). The fumigation toxicity and bioactivity bioassay were investigated using vapor-phase test. Experiment was performed under completely randomized design (CRD) with 4 replications. Adult mortality, number of eggs and adult emergence of F1 progeny of C. maculatus were recorded. Chemical compounds of essential oils from dried seeds and fresh leaves of P. nigrum and P. retrofractum were determined at 22-27 components (90.34-93.27%). Major compounds in dried seeds and fresh leaves of P. nigrum and P. retrofractum were alpha-bergamotene, caryophyllene, beta-selinene, germacrene D, naphthalene, undecane, 5-octadecene, cyclohexene, limonene and 2-beta-pinene. Both essential oils contained limonene, linalool, caryophyllene and naphthalene in seeds and leaves. These four components showed insecticidal properties. Essential oils at concentrations of 5 µL/L air P. nigrum and 10 µL/L air P. retrofractum extracted from dried seeds were more effective in oviposition inhibition and adult emergence of C. maculatus than essential oils extracted from fresh leaves. P. nigrum essential oil from dried seeds at a concentration of 5 µL/L air was the highest efficiency of oviposition inhibition with 55.17% and adult emergence inhibition of 71.09% of C. maculatus. This suggested that P. nigrum essential oil extracted from dried seeds could be used for protection on C. maculatus in stored grain.