Toxicity and repellency of (e/z)-3-butylidenephthalide: a natural compound isolated from ligusticum porteri root extract evaluated against imported fire ants (hymenoptera: formicidae)

Authors: ALI, ABBAS - University Of Mississippi; SHAH, FARHAN - University Of Mississippi; KHAN, IKHALAS - University Of Mississippi

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2024
Publication Date: 10/23/2024
Citation: Ali, A., Shah, F.M., Khan, I.A. 2024. Toxicity and repellency of (e/z)-3-butylidenephthalide: a natural compound isolated from ligusticum porteri root extract evaluated against imported fire ants (hymenoptera: formicidae). Insects. 15,11,828.
DOI: https://doi.org/10.3390/insects15110828

Interpretive Summary: Imported fire ants are native to South America, they were introduced into the southern United States in the early 20th century. Because of their overly aggressive behavior, increasing populations of fire ants have become a major safety concern and a risk for wildlife, agriculture, forestry, and ecological environments. Synthetic chemical baits and contact insecticides are used to control fire ants that are causing environmental contamination. Because of concern for potential environmental contaminations of synthetic chemicals, there has been an increasing research interest in relatively non-toxic natural products including secondary plant metabolites. Plant-derived natural products can offer a multitude of novel chemistries that can be effective as repellents and toxicants. Repellents can potentially be used in quarantine treatments for preventing fire ants from reentering treated nursery stocks. We tested (E/Z)-3-butylidenephthalide, a natural compound that was isolated from ethanolic extract of Ligusticum porteri roots, for repellency and toxicity against workers of imported fire ants. E/Z)-3-butylidenephthalide showed digging suppression and toxicity against imported fire ants. Digging suppression and toxicity properties of (E/Z)-3-butylidenephthalide makes it a unique and effective tool for the management of fire ants. The behavioral changes caused by exposure to (E/Z)-3-butylidenephthalide result in disorientation which suppresses the digging ability while the toxicity kills the ants. Further studies will be conducted to test the residual toxicity and digging suppression under field conditions to explore the potential of different (E/Z)-3-butylidenephthalide formulations as imported fire ant population management tool.

Technical Abstract: Imported fire ants are pests of significant importance especially in southern United States. We tested (E/Z)-3-butylidenephthalide, a natural compound that was isolated from ethanolic extract of Ligusticum porteri roots as repellent against workers of imported fire ants. Series of dosages were tested starting from 156 µg/g to the dose where the treatment failed. Workers removed significantly less sand from the vials treated with (E/Z)-3-butylidenephthalide in digging bioassay as compared to control. Based on sand removal, red imported fire ant workers showed digging suppression in (E/Z)-3-butylidenephthalide treatments at serial dosages of 19.5 to 0.6 µg/g than the solvent control whereas the amount of sand removed at 0.3 µg/g was similar to the solvent control. Black imported fire ants showed repellency at serial dosages ranging between 19.5 to 0.15 µg/g whereas the hybrid imported fire ants showed repellency at serial dosages ranging between 19.5 to 4.9 µg/g. In DEET treatments, red and black imported fire ants showed repellency at dosages of 125 to 62.5 µg/g, whereas the treatment failed at the dose of 15.6 µg/g in hybrid fire ants. (E/Z)-3-butylidenephthalide with LC50 values of 11 and 16.4 µg/g was toxic against red and black imported fire ants, respectively, followed by hybrid imported fire ant (LC50 = 104.7 µg/g). Fipronil with LC50 values of 0.49, 0.33 and 0.53 µg/g against red, black and hybrid fire ants respectively was more toxic than (E/Z)-3-butylidenephthalide. High repellency and toxicity of (E/Z)-3-butylidenephthalide against fire ants makes it a natural compound of interest for further studies under field conditions.