# Preliminary Evaluation of the Toxic Effects of Essential Oils as Natural Pesticides Against Maize Weevil (Sitophilus zeamais) and Its Fungal Pathogens

## TL;DR

This study shows that eucalyptus essential oil is a powerful natural pesticide against maize weevils and their fungi, outperforming lantana oil.

## Contribution

The study introduces eucalyptus oil as a dual-action biopesticide against maize weevils and their fungal pathogens.

## Key findings

- Eucalyptus oil achieved 100% weevil mortality at 5% concentration and inhibited fungal growth by up to 93%.
- Lantana oil also killed weevils at 10% concentration but was less effective as an antifungal agent.
- Eucalyptol, the main component of eucalyptus oil, is likely responsible for its high efficacy.

## Abstract

Essential oils from eucalyptus (Eucalyptus globulus) and lantana (Lantana camara) were explored as sustainable, dual-action biopesticides against the maize weevil (Sitophilus zeamais) and its associated fungal pathogens. Both oils proved to be potent insecticides, achieving 100% weevil mortality at a 10% concentration within 24 hrs. However, eucalyptus oil was significantly more effective overall: it maintained 100% mortality even at a lower 5% concentration and acted as a superior antifungal agent, inhibiting fungal growth (including the dominant species, Fusarium solani) by up to 93%. Chemical analysis suggests this higher efficacy is attributable to its primary constituent, eucalyptol (52.8%), leading to the conclusion that Eucalyptus globulus essential oil is a promising natural control agent for both the weevils and the fungi they harbor.

To control maize weevils (Sitophilus zeamais), a major pest of stored grains, this study explores the use of essential oils from Eucalyptus globulus and Lantana camara as natural biopesticides. Given the risks of synthetic pesticides, these oils offer a sustainable alternative. The research first identified ten fungal pathogens associated with the weevils, including the dominant species, Fusarium solani. Preliminary results showed that both oils were then tested for their ability to kill the fungi and the weevils. Eucalyptus globulus oil proved to be a superior antifungal agent, inhibiting fungal growth by up to 93%, significantly outperforming Lantana camara oil. Both oils demonstrated potent insecticidal properties, achieving 100% weevil mortality at a 10% concentration within 24 hrs. However, Eucalyptus oil was more effective, maintaining 100% mortality even at a lower 5% concentration, unlike Lantana oil. Chemical analysis showed that Eucalyptus oil’s high effectiveness may be associated with its main component, eucalyptol (52.8%). Lantana oil had a more varied composition, with caryophyllene (31%) as its primary constituent. The findings suggest that Eucalyptus globulus essential oil is a promising, two-in-one biopesticide capable of controlling both maize weevils and their associated fungal pathogens.