Toxicity and repellency of magnolia grandiflora seed essential oil and selected pure compounds against the workers of hybrid imported fire ants

Authors: ALI, ABBAS - University Of Mississippi; Chen, Jian; KHAN, IKHLAS - University Of Mississippi

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2021
Publication Date: 1/20/2022
Citation: Ali, A., Chen, J., Khan, I.A. 2022. Toxicity and repellency of magnolia grandiflora seed essential oil and selected pure compounds against the workers of hybrid imported fire ants. Journal of Economic Entomology. 115(2):412-416. https://doi.org/10.1093/jee/toab262.
DOI: https://doi.org/10.1093/jee/toab262

Interpretive Summary: Imported fire ants, including red imported fire ants, black imported fire ants, and their hybrid, are significant invasive pest ants, which causes about $7.5 billion economic annual loss in the Unite State. Synthetic insecticides continue to be a main approach for battling invasive pest ants. Due to an ever-increasing public concern for negative impacts of synthetic insecticides, new environmentally friendly products and methods are needed to reduce the risk of insecticides to human health and the environment, and to lessen our dependence on synthetic insecticides. In this study, the repellency and toxicity of southern magnolia essential oil and two chemical components,1-decanol and 1-octanol,were evaluated against hybrid imported fire ants. All three tested products showed significantly higher repellency than DEET, a common insect repellant. Among three tested substances, 1-Decanol was the most toxic to fire ants followed by 1-octanol. High repellency and toxicity of 1-decanol make it a promising compound to be used in developing new products for fire ant control.

Technical Abstract: In our natural products screening program, we tested Magnolia grandiflora seed essential oil and its pure compounds that were active against mosquitoes, for their repellency and toxicity against workers of hybrid imported fire ants using a sand digging repellent bioassay and a new toxicity bioassay. Series of dosages were tested starting from 156 µg/g to the dosage where the product failed Workers removed significantly less sand from the vials with Magnolia grandiflora seed essential oil and 1-octanol treated sand at dosages of 156, 78, 39, 19.5, 9.8, and 4.9 µg/g than the solvent control whereas the amount removed at 2.4, 1.2 and 0.6 µg/g was similar to the solvent control. In 1-decanol treatments, workers removed significantly less sand at dosages of 156, 78, 39,19.5, 9.8, 4.9, 2.4, 1.2, 0.6, 0.31 and 0.15 µg/g than the solvent control whereas the removal of sand at the dose of 0.08 µg/g was similar to solvent control. In DEET treatments, workers removed significantly less sand from the vials at dosages of 156, 78, and 39 µg/g than the solvent control whereas the quantity of removed sand at 19.5 µg/g was similar to solvent control. Based on the mean amount of sand removed, all the three products tested in this study showed significantly higher repellency than DEET. Pure compounds 1-decanol and 1-octanol, present in seed essential oil showed toxicity against workers and were further evaluated for dose-response. 1-Decanol with LC50 of 140.6 µg/g was the most toxic natural compound followed by 1-octanol (LC50 = 326.9 µg/g) at 24-h posttreatment. Permethrin with LC50 of 2.74 µg/g showed much higher toxicity than these natural compounds. High repellency and toxicity of 1-decanol makes it a compound of interest for further studies under field conditions.