Insecticidal Efficacy of <i>Satureja hortensis</i> L. and <i>Satureja khuzistanica</i> Jamzad Essential Oils Against <i>Callosobruchus maculatus</i> (F.).

Abstract

The cowpea weevil, <i>Callosobruchus maculatus</i> (F.), stands out as one of the most destructive field-to-storage pests of leguminous crops. This study investigates the potential of essential oils derived from two <i>Satureja</i> species, <i>Satureja hortensis</i> L. and <i>Satureja khuzistanica</i> Jamzad, for managing <i>C. maculatus</i>. Bioassay results revealed that both <i>S. hortensis</i> (72 h LC₅₀ = 0.20 µL/g) and <i>S. khuzistanica</i> (72 h LC₅₀ = 0.19 µL/g) essential oils exhibited significant toxicity against <i>C. maculatus</i> adults. The essential oils extended development time, reduced adult longevity, and decreased fecundity of the pest. Key population parameters, including intrinsic growth rate (<i>r</i>) and net reproductive rate (<i>R</i>₀), were significantly lowered, particularly by <i>S. hortensis</i> essential oil. Age-specific survival (<i>l_x</i>) and fecundity (<i>m_x</i>₎ rates were also declined in treated groups, with delayed reproductive peaks compared to controls. Chemical analyses of <i>S. hortensis</i> and <i>S. khuzistanica</i> essential oils indicated that carvacrol (30.9% and 62.9%, respectively), γ-terpinene (25.5% and 4.3%), <i>p</i>-cymene (9.7% and 7.9%), and thymol (3.7% and 9.3%) were the major components. Hierarchical cluster analysis (HCA) was carried out to compare and contrast the compositions with previous works. The results demonstrated that <i>S. hortensis</i> and <i>S. khuzistanica</i> essential oils, given their lethal and sublethal effects against <i>C. maculatus</i>, can be introduced as natural alternatives to hazardous chemical insecticides, highlighting the need for further research in this field.