Repellency, toxicity, and physiological actions of low molecular weight basic amines in insects

Authors: YANG, LIU - University Of Florida; DEMARES, FABIEN - University Of Florida; Norris, Edmund; BLOOMQUIST, JEFFREY - University Of Florida

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2025
Publication Date: 7/11/2025
Citation: Yang, L., Demares, F., Norris, E.J., Bloomquist, J.R. 2025. Repellency, toxicity, and physiological actions of low molecular weight basic amines in insects. Pest Management Science. 80(11):5648-5655. https://doi.org/10.1002/ps.8281.
DOI: https://doi.org/10.1002/ps.8281

Interpretive Summary: Select basic amines were tested for their potential to act as repellents and insecticides on a variety of different insect classes. In vapor phase exposure, these compounds produced repellency, narcosis, knockdown, and death at increasing doses, respectively. While these compounds were good repellents and insecticides when insects were challenged via vapor exposures, they were not very toxic when applied directly to the cuticle of the insect, likely due to their relatively high volatility. In electrophysiological studies, basic amines produced neuroexcitation and nerve block, although acted in unique ways depending on the insect or tissue exposed. These results suggest that select basic amines have diverse activity on a number of targets within insect nervous systems. This study helps to further explain how basic amines act on insects and explores their potential as future insect control agents. More work is needed to evaluate these compounds on other insect pests and in diverse semi-field and field deployments.

Technical Abstract: In this study, the behavioral responses and toxicity of three basic amines, 1-methylpiperazine, 1-methylpyrrolidine and triethylamine were investigated. In vapor phase exposures, these compounds showed repellency of Aedes aegypti mosquitoes, followed by narcosis, knockdown, and paralysis, all increasing with exposure time and dose. Knockdown by triethylamine, but not the other amines, was reversible. Low topical toxicities were observed from all three basic amines, probably because of rapid evaporation from the cuticle. Electrophysiological experiments showed a blocking effect on nerve discharge of Drosophila melanogaster larval CNS with little evidence of hyperexcitation. Block of Kv2 channel currents occurred at similar concentrations. The rank order of potency for these effects was consistent with the KD50 for vapor toxicity. A role of K+ channels in the action of basic amines was supported by CNS recordings of a Shaker Kv1 mutant exposed to TEA, where instead of block, a hyperexcitation of nerve firing was observed. Further tests on nicotinic acetylcholine receptor suggested that basic amines may also act as weak antagonists. Experiments on cockroach leg mechanoreceptors showed neuronal excitation and on mosquito antennae strong electroantennogram signals and an augmentation of blank air responses after a single puff of basic amine. Finally, the similarity of poisoning symptoms of triethylamine with the known chordotonal organ modulator, pymetrozine in crickets was of interest, and future studies of these basic amines on chordotonal organ should be conducted.