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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Mosquito and Fly Research » Research » Publications at this Location » Publication #432599
Research Project: Integrated Management of Resistance and Population Expansion of Disease Vector and Nuisance Mosquitoes

Location: Mosquito and Fly Research

Title: Pepper constituents enhance the toxicity and neurophysiological effects of natural pyrethrins in mosquitoes

Author
item Norris, Edmund
item BLOOMQUIST, JEFFREY - University Of Florida

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2026
Publication Date: 5/7/2026
Citation: Norris, E.J., Bloomquist, J. 2026. Pepper constituents enhance the toxicity and neurophysiological effects of natural pyrethrins in mosquitoes. Insects. 17:5(510). https://doi.org/10.3390/insects17050510.
DOI: https://doi.org/10.3390/insects17050510

Interpretive Summary: Scientists at the USDA-ARS Mosquito and Fly Research Unit (MFRU) partnered with University of Florida (UF) scientists to develop plant-based synergists that improve the performance of natural pyrethrins against resistant Aedes aegypti populations. Rather than relying solely on new insecticides, the team focused on restoring the effectiveness of already-commercialized compounds. Researchers found that extracts from black pepper (Piper nigrum) and Sichuan pepper (Zanthoxylum spp.) increased pyrethrin efficacy more than 13-fold in adult female mosquitoes. Importantly, synergism was also observed directly at the mosquito central nervous system (CNS), demonstrating that these extracts act not only by reducing detoxification metabolism but also by directly modifying insect nerve activity. This research benefits American farmers and ranchers by helping extend the useful life of pyrethroid-based products widely used to control mosquitoes and biting flies affecting livestock. By restoring efficacy against resistant populations, these plant-derived synergists could reduce application rates, lower costs, and delay resistance development. Because they enhance already-registered chemistries, this approach also supports faster regulatory deployment and strengthens integrated pest management strategies. Ultimately, this work provides practical tools to protect livestock health, productivity, and rural economic stability.

Technical Abstract: Control of resistant mosquito populations may be approached by the development of novel synergists to improve the performance of already commercialized compounds. Extracts of black pepper (Piper nigrum), Cha Plu (Piper sarmentosum), and Sichuan pepper (Zanthoxylum spp.) synergized natural pyrethrins applied topically to Aedes aegypti females. Both black pepper and Sichuan pepper extracts synergized natural pyrethrins over 13-fold. compSynergism was also observed directly on the mosquito larval central nervous system (CNS), suggesting this effect is an important contributing factor distinctunique from that of reduced metabolism. Piperine, from black pepper, and '-hydroxysanshool from Sichuan pepper, both synergized natural pyrethrins on susceptible CNS, but only piperine was capable of synergizing natural pyrethrins on the CNS of a pyrethroid-resistant strain of Ae. aegypti, indicating that these molecules possess slightly different mechanisms of action. Further, it was observed that both piperine and a-hydroxysanshool (10 µM) diminished action potential amplitudes in electrically-stimulated cockroach axons. However, a-hydroxysanshool depolarized the axon resting membrane potential, whereas piperine did not.