Insecticidal properties of lemon grass, clove and star anise essential oils and their main chemical compounds against maize weevil (Sitophilus zeamais Motschulsky)

Abstract

The use of plant essential oils (EOs) as an alternative to traditional pesticides for controlling stored product pests has gained increasing attention due to the potential to reduce insecticide resistance and toxic residues in products and the environment. In this study, the EOs of lemon grass (Cymbopogon citratus), clove (Syzygium aromaticum), and star anise (Illicium verum) with their main chemical compounds were evaluated for insecticidal properties in both toxic and repellent forms against maize weevil (Sitophilus zeamais). The chemical compositions of the EOs were analyzed using gas chromatography-mass spectrometry (GC-MS). The results obtained in this study indicate that the major components in lemon grass EO are citral (84.93%; cis-citral (49.10%) and trans-citral (35.83%)), while eugenol (88.66%) and trans-anethole (95.28%) were the major compounds in clove and star anise EOs, respectively. The EOs demonstrated higher toxicity against adult maize weevils compared to their main chemical compounds. The clove EO showed the greatest fumigation potential to kill maize weevils, with an LC50 of 3.044 μL L-1 air, followed by the EOs of star anise (4.925 μL L-1 air) and lemon grass (5.769 μL L-1 air). The chemical compounds eugenol, transanethole, and citral had LC50 values of 4.640, 5.441, and 6.433 μL L-1 air, respectively. Lemon grass EO and citral showed their potential for repelling maize weevils, with the highest repellence response observed at a concentration of 0.12 μL cm-2 (over 75% response). Overall, this study indicates that clove EO may be effective for killing maize weevils, while lemon grass EO may be suitable for repelling this insect.