Matricaria chamomilla Essential Oils: Repellency and Toxicity against Imported Fire Ants (Hymenoptera: Formicidae)

Matricaria chamomilla flower essential oils (EOs) blue Egyptian (EO-1), chamomile German CO2 (EO-2), and chamomile German (EO-3) and the pure compound alpha-bisabolol were evaluated against red imported fire ants (RIFA), Solenopsis invicta Buren, black imported fire ants, S. richteri Forel (BIFA), and hybrid imported fire ants (HIFA) for their repellency and toxicity. A series of serial dilutions were tested starting from 125 mu g/g until the failure of the treatment. Based on the amount of sand removed, EO-1 showed significant repellency at dosages of 7.8, 7.8, and 31.25 mu g/g against RIFA, BIFA, and HIFA, respectively. EO-3 was repellent at 3.9, 7.8, and 31.25 mu g/g against BIFA, RIFA, and HIFA, whereas alpha-bisabolol was active at 7.8, 7.8, and 31.25 mu g/g against BIFA, HIFA, and RIFA, respectively. DEET (N, N-diethyl-meta-toluamide) was active at 31.25 mu g/g. Toxicity of EOs and alpha-bisabolol was mild to moderate. For EO-1, LC50 values were 93.6 and 188.11 mu g/g against RIFA and BIFA; 98.11 and 138.4 mu g/g for EO-2; and 142.92 and 202.49 mu g/g for EO-3, respectively. The LC50 of alpha-bisabolol was 159.23 mu g/g against RIFA. In conclusion, M. chamomilla EOs and alpha-bisabolol offer great potential to be developed as imported fire ant repellents.