Coconut fatty acids exhibit strong repellency and week-long efficacy against several urban pest arthropods of the southwestern United States

Authors: AGNEW, JOHN - New Mexico State University; GORZELSKI, ASHTON - New Mexico State University; Zhu, Junwei - Jerry; ROMERO, ALVARO - New Mexico State University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2023
Publication Date: 5/5/2023
Citation: Agnew, J., Gorzelski, A., Zhu, J.J., Romero, A. 2023. Coconut fatty acids exhibit strong repellency and week-long efficacy against several urban pest arthropods of the southwestern United States. Pest Management Science. https://doi.org/10.1002/ps.7531.
DOI: https://doi.org/10.1002/ps.7531

Interpretive Summary: The southwestern United States is home to a variety of arthropods suited for the desert climate including a wide variety of nuisance pests including the Turkestan cockroach, the triatomid Triatoma rubida, and the Arizona Bark Scorpion that invade peri-urban and domestic dwellings with the potential of some of them to cause direct illness to humans and animals through bites and stings. Management of the above arthropods relies on the application of chemical insecticides, primarily pyrethroids in the form of sprays or aerosol, which are applied in and around building exteriors. However, on the effectiveness of insecticide treatments against these peridomestic pests. Perimeter application of insecticides was less effective at reducing adult abundance when compared with an integrated approach which included sanitation and landscape management. Environmentally-sound strategies for pest control that consider alternative methods such as using botanical pest repellent and biopesticide (coconut fatty acids) that supplement the tool-set for the control of these pests are particularly in demand in sensitive areas such as schools, parks and hospitals.

Technical Abstract: This study investigates the behavioral responses of these common urban pests to recently discovered coconut fatty acids to evaluate the fresh and long-lasting repellent effect as a means of controlling these nuisance arthropods. We first screened all coconut fatty acid constituents for their repellent effect as fresh residues (10% mixtures applied at 1 mg/cm2) using bioassay recordings for kissing bugs and overnight choice tests for Turkestan cockroaches and scorpions. We then conducted choice tests for all three arthropod models using aged residues of whole coconut fatty acid mixture, lavender, and a mixture of the two (10% mixtures applied at 1 mg/cm2). Lastly, we conducted video recording assays on Turkestan cockroaches and kissing bugs and choice test assays on the scorpions using lower application rates (0.1 and 0.01 mg/cm2) residues of fresh whole coconut fatty acid mixture. What we found is that all coconut fatty acid constituents strongly repelled, >80%, of the tested arthropods in most cases, significantly, excluding caprylic acid methyl ester. We then also determined that the whole coconut fatty acid mixture significantly repelled all arthropods for at least 7 days after treating and that the addition of lavender oil, to mask scent, did not reduce this repellent effect and was shown to also be repellent by itself. Finally, it was determined that lower concentrations did significantly repel all arthropods when applied at 0.1 mg/cm2 and repelled scorpions and kissing bugs when applied at 0.01 mg/cm2. Based on our findings, coconut fatty acid and its constituents could open more avenues for control or be used alone as an alternative to repel these nuisance insects in urban settings.