In Vitro Termiticidal Activity of Medicinal Plant Essential Oils Against Microcerotermes crassus

Termites are destructive structural pests causing significant economic losses worldwide. Although synthetic termiticides are effective, their extensive use raises environmental and health concerns, highlighting the need for safer, sustainable alternatives. This study evaluated the contact toxicity and repellency in a closed system of essential oils (EOs) from clove (<i>Syzygium aromaticum</i>), cinnamon (<i>Cinnamomum zeylanicum</i>), and star anise (<i>Illicium verum</i>) against <i>Microcerotermes crassus</i> workers. Chemical constituents (eugenol and anethole) were characterized by GC-MS/MS, and their activities were compared with those commercial termiticides (fipronil and cypermethrin). Clove and cinnamon oils exhibited strong toxicity, with LC₅₀ values decreasing from 208.6 to 70.6 µL/L and from 362.6 to 130.5 µL/L, respectively, over 24 h. Both achieved LT₅₀ values below 10 h at 250 µL/L and over 80% repellency at 100-500 µL/L within 3-12 h. Eugenol, the major constituent, showed comparable activity. In contrast, star anise oil, dominated by anethole, displayed weaker repellency but measurable termiticidal effects with a slower onset. These findings indicate that eugenol-rich oils may provide rapid-contact activity. In contrast, anethole-rich oils may offer slower but measurable termiticidal effects, suggesting distinct potential roles in future formulation development. The findings provide a foundation for developing nanoemulsion-based botanical termiticides with improved stability and field performance.