Repellency of an Over-the-counter Essential Oil Product from China against Workers of Red Imported Fire Ants

Authors: Chen, Jian

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2008
Publication Date: 1/5/2009
Citation: Chen, J. 2009.Repellency of an Over-the-counter Essential Oil Product from China against Workers of Red Imported Fire Ants. Journal of Agriculture and Food Chemistry. 57(2):618-622.

Interpretive Summary: Red imported fire ant, Solenopsis invicta Buren is a serious problem to human health, agriculture, and wildlife. Synthetic insecticides are commonly used in red imported fire ant management, which can be a source of environmental concern. In order to reduce the amount of insecticide entering the environment, there has been increasing interest in using non-insecticidal control products, such as fire ant repellants. We found an over-the-counter essential oil product to be a strong repellant to red imported fire ants. This study will ultimately benefit the public by facilitating the development of more effective fire ant repellent products.

Technical Abstract: Repellency of an over-the-counter essential oil product from China, and its major components against workers of red imported fire ants, Solenopsis invicta Buren, was evaluated using an ant digging bioassay. Three concentrations (1.0, 10.0, and 100.0 mg/kg in sand) of the product were tested. At 100.0 mg/kg, the digging suppress index (DSI) was 1.0 ± 0.00 (mean ± SE) for all 6 test colonies, indicating this product produced a complete digging suppression; at 10 mg/kg, DSI was 0.22 ± 0.089 to 0.75 ± 0.12 and significant repellency occurred against 5 of 6 colonies; and at 1.0 mg/kg, DSI was 0.21 ± 0.091 to 0.38 ± 0.14 and significant repellency occurred against 4 of 6 colonies. The chemical components of this product were analyzed using gas chromatography – mass spectrometry (GC-MS). Camphor, eucalyptol, eugenol, menthol, methyl salicylate, and phenylethanol were identified. A Digging bioassay was also conducted on each of those identified compounds at concentrations of 1.0, 10.0, and 100.0 mg/kg. Based on pooled data from three colonies, each component significantly suppressed the digging behavior at 100 mg/kg. Eugenol, menthol and methyl salicylate significantly suppressed the digging at 10 mg/kg. At 1.0 and 10.0 mg/kg, DSI for eucalyptol was -0.039 ± 0.032 and -0.050 ± 0.021 respectively. The negative DSI indicated a digging facilitation. However, only at 10.0 mg/kg, such facilitation was statistically significant.