Insecticidal effects of two Tunisian diatomaceous earth loaded with Thymus capitatus (L.) Hoffmans and Links as an ecofriendly approach for stored coleopteran pest control

ABSTRACT

This study investigated composition and toxicity of Thyme EOs against two main stored grain insect pests. Carvacrol was distinguished as a major compound (78.34%). In laboratory tests, EOs applied by both direct contact and fumigant tests was more toxic to L. serricorne than T. castaneum. The EOs were also tested combined with two Tunisian Diatomaceous earths (DEs) against T. castaneum. The LC₅₀ was 6.28 µL/L air for natural preparation EO/R1, 5.90 µL/L air for EO/R2 and 121.17 for crude EOs by fumigant test, respectively. While, contact test revealed that natural DEs; dust act as an insecticide with ‘LC₅₀ʻ values of 3.22 and 0.29 µL/cm²f or R1 and R2, respectively. Moreover, a significant difference was noted between crude EO, EO/R1 and EO/R2. Overall, the enhancement of the Tunisian DEs’ insecticidal activity by its mix with EOs may be a promising active substance as a stored grain protectant.

KEYWORDS:

• Stored product beetle
• essential oil
• diatomaceous earth
• Thymus capitatus Hoff
• insecticidal activity

Acknowledgements

The authors are grateful to Ms. Besma Ayadi Hedfi Factory Director of the Tunisian milling company RANDA.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Tunisian Ministry of Higher Education and Scientific Research under Grant [VRR:1515-2019].