Eugenol diffusion coefficient and its potential to control Sitophilus zeamais in rice

Area of Science:

• Agricultural Entomology
• Natural Product Chemistry
• Pest Management

Background:

• Eugenol, a compound found in clove oil, shows promise as a natural insecticide.
• Understanding eugenol's diffusion and efficacy is crucial for developing eco-friendly pest control strategies.
• Sitophilus zeamais (maize weevil) is a significant pest of stored rice.

Purpose of the Study:

• To determine the diffusion coefficient of eugenol from pure sources and clove essential oil through rice grain.
• To analyze the chemical composition of eugenol and clove essential oil.
• To evaluate the insecticidal efficacy of diffused eugenol against Sitophilus zeamais.

Main Methods:

• Solid phase microextraction (SPME) coupled with gas chromatography (GC) for eugenol quantification.
• Measurement of eugenol diffusion coefficient through rice grain.
• Chemical analysis of volatile compounds in eugenol and clove essential oil.
• Insect mortality bioassays with Sitophilus zeamais exposed to diffused eugenol.

Main Results:

• The diffusion coefficient of eugenol through rice was determined as 1.09 × 10⁻³ cm²/s, with no significant difference between pure eugenol and clove essential oil.
• Clove essential oil contained 74.25% eugenol, confirming it as the major volatile component.
• Exposure to diffused pure eugenol resulted in significantly higher maize weevil mortality (~37%) compared to eugenol diffused from clove oil (~11%).

Conclusions:

• Eugenol's diffusion through rice is consistent, making it a viable fumigant.
• Pure eugenol demonstrates greater insecticidal activity against Sitophilus zeamais than when diffused from clove essential oil.
• Eugenol holds potential as a natural fumigant for stored product protection.