Abstract
Sitophilus zeamais (Motschulsky) is considered as one of the most destructive foodstuff pests. Due to their efficiency, low toxicity for mammalians and low environmental impact, plant-derived essential oils (EOs) are promising tools for pest control. In particular, the OEs extracted from Lamiaceae are considered among the most bioactive in terms of repellent and/or insecticidal effect. Here, we investigated the repellence of the EOs extracted from two aromatic plant species typical of the flora of the Ecuadorian Andes, Clinopodium tomentosum and C. nubigeum, against adults of S. zeamais. The behavioral assays carried out at concentrations ranging from 0.7 to 23.9 μL L−1 air in a two-way static olfactometer showed a significant repellent effect starting from the concentration of 8.4 mL L−1 air both for the EO of C. nubigenum and C. tomentosum. We also carried out a complete structural analysis of the antenna of S. zeamais using scanning (SEM) and transmission electron microscopy (TEM), in order to characterize the olfactory sensilla equipment. In this species, there is no sexual dimorphism also as regards to the antennal morphology and the sensilla type and distribution. We identified six type of sensilla, among which at least three types (Sensillum Trichoideum 1, Sensillum Trichoideum 2 and Grooved Peg Sensillum) can be considered as olfactory. Electroantennography (EAG) recordings carried out on S. zeamais revealed a positive dose-response to both EOs, without differences between the two sexes.
Highlights
Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), the maize weevil, is one of the main pests of stored grain, causing either quantitative, and qualitative damages in most part of the world [1,2]
We investigated the activity of the essential oils (EOs) extracted from two species of Lamiaceae belonging to the genus Clinopodium, C. nubigenum (Kunth) Kuntze and C. tomentosum (Kunth) Govaerts
We report the behavioral effects of C. nubigenum and C. tomentosum EOs on the maize weevil S. zemais
Summary
Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), the maize weevil, is one of the main pests of stored grain, causing either quantitative (in terms of loss of stored products), and qualitative (in terms of reduced quality of stored grains) damages in most part of the world [1,2]. From the closely related species, S. granarius L., but analogously to the rice weevil S. oryzae L., the maize weevil is able to fly, and can reach actively the grain storage facilities to initiate the infestation [3,4,5]. For this species, several control methods have been developed, from the use of pesticides (according to different formulations, including fumigations) to physical control methods (controlled atmosphere, low temperatures) [6,7,8,9]. EOs from Hyptis suaveolens L. (Lamiaceae) and Humulus lupulus L. (Cannabaceae) exhibited a repellent activity against S. granarius [21,22], whilst EOs from
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