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

Authors: SHAH, FARHAN MAHMOOD - University Of Mississippi; GUDDETI, DILEEP - University Of Mississippi; PAUDEL, PRADEEP - University Of Mississippi; Chen, Jian; LI, XING-CONG - University Of Mississippi; KHAN, IKHLAS - University Of Mississippi; ALI, ABBAS - University Of Mississippi

Submitted to: Molecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2023
Publication Date: 7/22/2023
Citation: Shah, F.M.; Guddeti, D.K.; Paudel, P.; Chen, J.; Li, X.-C.; Khan, I.A.; Ali, A. Matricaria chamomilla Essential Oils: Repellency and Toxicity against Imported Fire Ants (Hymenoptera: Formicidae). Molecules 2023, 28, 5584. https://doi.org/10.3390/molecules28145584
DOI: https://doi.org/10.3390/molecules28145584

Interpretive Summary: The red and black fire ants are two significant pest ants in the USA. Hybridization occurs between these two species and the resultant hybrid is also an important pest. Currently, fire ant management heavily depends on the synthetic insecticides. The use of synthetic pesticides always comes with a cost for the environment and new environmentally friendly products and methods are very much desired. In this study, three essential oils (EOs) from chamomile flowers (Matricaria chamomilla), Chamomile Oil Blue Egyptian (EO-1), Chamomile German CO2 (EO-2), and Chamomile German Essential Oil (EO-3) were tested for repellency and toxicity against workers of hybrid imported fire ants. All three essential oils showed significant repellency. Since high content of a-bisabolol found in EO-2, a-bisabolol was also tested. Both EO-2 and a-bisabolol showed significantly higher repellency than DEET, a well-known insect repellant. EO-3 and a-bisabolol caused >93% mortality at the dose of 500 µg/g at 24-h posttreatment. These data suggest that a-bisabolol and M. chamomilla essential oils with a high content of a-bisabolol have the potential to be used as repellents against hybrid imported fire ant workers.

Technical Abstract: In our natural products screening program, we tested three essential oils (EOs) from chamomile flowers (Matricaria chamomilla), Chamomile Oil Blue Egyptian (EO-1), Chamomile German CO2 (EO-2), and Chamomile German Essential Oil (EO-3) repellency against workers of hybrid imported fire ants. A series of dosages were tested, starting from 125 µg/g to the dose where the treatment failed. Workers removed significantly less sand from the vials with EO-2 treated sand at 125–31.25 µg/g than the solvent control, whereas the amount of sand removed at 15.6–3.9 µg/g was similar to the solvent control. In treatments with EOs-1 and 3, significantly less sand was removed at dosages of 125 and 62.5 µg/g, respectively, than the solvent control. In DEET (N, N-diethyl-meta-toluamide) treatments, the removal of sand by workers was significantly less at serial dosages of 125 - 31.25 µg/g than the solvent control. To delineate the variation in repellency by three EO samples, a qualitative and quantitative analysis of the oils was performed by GC-MS. The result depicted a high content of a-bisabolol (81.85%) in EO-2 and a-bisabolol oxide A in EOs-1 and 3 with 49.19% and 27.83% content, respectively. Based to high percentage of a-bisabolol in CO-2, the pure compound a-bisabolol was also tested. In a-Bisabolol treatments, workers removed significantly less sand at serial dosages of 125–7.8 µg/g than the solvent control whereas the removal of sand at a dose of 3.9 µg/g was similar to the solvent control. Based on the mean amount of sand removed, both EO-2 and a-bisabolol showed significantly higher repellency than DEET. A mortality of 37%, 87%, 93%, and 97% was noted in hybrid imported fire ant workers from EO-2, EO-1, a -bisabolol, and EO-3 at the dose of 500 µg/g at 24-h posttreatment, respectively. These data suggest that a-bisabolol and M. chamomilla essential oils with a high content of a-bisabolol have the potential to be used as repellents against hybrid imported fire ant workers.