Preliminary Assessment of Repellency and Toxicity of Essential Oils against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) on Stored Organic Corn Grains

Abstract

Insect infestation of cereal grains during post-harvest storage not only causes significant grain loss, but also reduces grain quality and makes grains more susceptible to mold infection. Synthetic pesticides are banned from being used in organic grain storage setting due to their high toxicity. The main insect damaging stored corn grains is maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). The purpose of this study was to evaluate insect repellency and insecticidal potentials of some generally recognized as safe (GRAS) essential oils (EOs) (including cinnamon, clove, thyme, oregano, and orange terpene oils) at concentrations of 1–20% against the maize weevil using an olfactometer and a simulated fumigation method, respectively. The olfactory tests show that cinnamon oil had the highest repellency (90%) to the weevils among the EOs tested. The insecticidal activity study indicates that maize weevil mortality increased with EO concentration and storage time with cinnamon, clove, and thyme oils being more effective. No weevil death was observed at 1% EOs; weevil mortality was 3.3–36% at 5%, which varied with the type of EO and storage time. At 10% or higher concentrations, all tested EO showed comparable or higher insecticidal activity than pirimiphos methyl-positive control at its recommended concentration (5 mg/kg corn). No significant increase in weevil mortality was observed with further increase in EO concentration, with exceptions of oregano oil and thyme oil. The highest weevil mortality levels were observed at week 7 for 15% cinnamon oil (100%) and eugenol (100%), followed by 20% thyme oil (93%). The study indicates that some EOs have great potential to serve as synthetic insecticide alternatives to protect organic corn grains from maize weevil damage during storage. This is important to food security, safety and environmental health.

Toxicity evaluation of essential oil of clove (Syzygium aromaticum) bud against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

“…Our study revealed 100% mortality reached with 10% concentration at 16 days of treatments. About 87% mortality of S. zeamais with 10% clove oil reached at 7 weeks of the treatments to maize grains and mortality further increased as the concentration increases to 15% (Eesiah et al 2022). However, when maize grain was treated with clove oil, 100% mortality of S. zeamais was achieved with 35μl g -1 within 48 h (Jairoce et al 2016).…”

“…S. zeamais avoided the clove essential oil treated areas and changed their direction with reduced respiratory rates (Haddi et al 2015, Plata-Rueda et al 2018. However, attraction to clove oil measured by olfactometer by Eesiah et al (2022) showed very low percent repellency of S. zeamais. Jumbo et al (2014) also reported less attractiveness with the dosage of clove oil tested.…”

“…Higher toxicity might be due to the closed condition of the scintillating vial where both contact as well as fumigation effect may have occurred which triggered high mortality with low volume. Furthermore, differential results also depended upon the plant species, their parts used for extraction, plant parts used at different growth stages, extraction methods, chemical constituents present in oils, concentrations and time of exposure (Lee et al 2001, Eesiah et al 2022.…”

Volatile metabolites from new cultivars of catnip and oregano as potential antibacterial and insect repellent agents

“…In addition, use of oregano essential oil for managing pests of importance has also been studied. Oregano essential oil has been reported to have either lethal or sublethal activity against major pests of importance such as the maize weevil (Sitophilus zeamais) (Eesiah et al, 2022), stored product weevil (Sitophilus granarius) (Plata-Rueda et al, 2022), red flour beetle (Tribolium castaneum) (Licciardello et al, 2013), blowfly (Calliphora vomitoria) (Bedini et al, 2021), bed bugs (Cimex lectularius) (Sharififard et al, 2018), mosquitoes (Aedes albopictus) (Giatropoulos et al, 2022) and ticks (Ixodes ricinus) (Soutar et al, 2019).…”

Cinnamon Oil Encapsulated with Silica Nanoparticles: Chemical Characterization and Evaluation of Insecticidal Activity Against the Rice Moth, Corcyra cephalonica

“…Several studies have focused on the potential use of essential oils (EOs) in the biological control of different insect pests since some are selective, safe to apply, biodegraded to nontoxic products, potentially less expensive, and have few effects on nontarget organisms and the environment (Isman 2000 ; Kim et al 2010 and Eesiah et al 2022 ). Many recent studies have been performed on the toxicity and biological effects of certain natural oils on different insect species, giving promising results (Mohamed et al 2020 ; Attia et al 2020a , b ; Elsayed et al 2022 and Sayed et al 2022 ).…”