Pest Control Using Essential Oils from Thyme and Lemongrass

Greg Howard
18th June, 2024

Pest Control Using Essential Oils from Thyme and Lemongrass

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Mohamed El Bachir El Ibrahimi University, Algeria, studied essential oils from Thymus pallescens and Cymbopogon citratus for pest control in stored maize
  • T. pallescens essential oil showed high insecticidal efficacy, killing 42.5-100% of maize weevils and red flour beetles
  • Combining T. pallescens and C. citratus oils increased pest mortality rates and reduced the amount needed for effective control
The recent study conducted by researchers at Mohamed El Bachir El Ibrahimi University, Algeria, focused on the chemical composition and insecticidal efficacy of essential oils (EOs) extracted from Thymus pallescens de Noé and Cymbopogon citratus Stapf. against two major post-harvest pests: the maize weevil (Sitophilus zeamais Motschulsky) and the red flour beetle (Tribolium castaneum Herbst)[1]. This study is significant in addressing the critical issue of pest management in stored grains, particularly maize, which is a staple food crop worldwide. The researchers identified carvacrol (56.04%) as the major constituent of T. pallescens EO and geraniol (20.86%) as the main component of C. citratus EO. These compounds were tested for their insecticidal properties through contact and fumigation methods. The study found that T. pallescens EO exhibited the highest efficacy, with corrected mortality rates ranging from 42.5-100% and 25-100% in S. zeamais, and corresponding lethal concentration (LC50) values of 17.7 µl/ml and 15 µL/L air, respectively. For T. castaneum, the corrected mortality rates were 42.5-100% and 20-100%, with LC50 values of 18.1 µl/ml and 15.5 µL/L air, respectively. The study's findings are consistent with previous research that highlighted the susceptibility of maize landraces to pests like S. zeamais[2]. This earlier study evaluated various maize varieties and found that landraces were more susceptible to weevil attacks compared to commercial varieties. The current study extends this knowledge by demonstrating that essential oils, particularly from T. pallescens, can effectively control these pests, offering a potential eco-friendly alternative to chemical pesticides. Additionally, the study aligns with earlier research on the red flour beetle, T. castaneum, which is known to spread fungal contaminants and increase mycotoxin levels in stored grains[3]. By effectively controlling T. castaneum, the essential oils could also mitigate the spread of harmful fungi, thereby improving the overall quality and safety of stored grains. The study also explored the combined use of T. pallescens and C. citratus EOs, revealing that combination treatments led to increased corrected mortality rates and significant reductions in LC50 values, ranging from 8.59 to 49.9% for both pest species. This finding is particularly noteworthy as it suggests that using a combination of EOs can enhance their insecticidal efficacy, potentially reducing the required doses and minimizing any adverse environmental impacts. In terms of methodology, the researchers conducted contact and fumigation assessments to evaluate the insecticidal activity of the EOs. They also analyzed energy biomarkers in the treated insects, finding significantly increased protein and carbohydrate contents and decreased lipid levels. These biochemical changes indicate that the EOs disrupt the metabolic processes of the pests, leading to their mortality. Previous studies have also shown the insecticidal potential of C. citratus EO. For instance, research on the control of the common housefly, Musca domestica, demonstrated that C. citratus oil, rich in citral and 1,8-cineole, exhibited high efficacy against housefly larvae and pupae[4]. This supports the current study's findings on the effectiveness of C. citratus EO against T. castaneum and S. zeamais. In conclusion, the study by Mohamed El Bachir El Ibrahimi University provides compelling evidence for the use of essential oils from T. pallescens and C. citratus as effective bio-insecticides against two major pests of stored maize. The findings suggest that these EOs, particularly when used in combination, could offer a sustainable and environmentally friendly alternative to traditional chemical pesticides, addressing both pest control and food safety concerns.



Main Study

1) Insecticidal activity of Thymus pallescens de Noë and Cymbogon citratus essential oils against Sitophilus zeamais and Tribolium castaneum.

Published 17th June, 2024

Related Studies

2) Resistance of maize landraces to the maize weevil Sitophilus zeamais Motsch. (Coleoptera: Curculionidae).

3) Isolation and Identification of Fungal Species from the Insect Pest Tribolium castaneum in Rice Processing Complexes in Korea.

4) Housefly (Musca domestica L.) control potential of Cymbopogon citratus Stapf. (Poales: Poaceae) essential oil and monoterpenes (citral and 1,8-cineole).

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