The Use of <em>Piper amalago</em> var. <em>amalago</em> as an Eco-Friendly Insecticide Synergist in the Management of <em>Aedes Aegypti</em>

Resistance to insecticides challenges the management of Ae. aegypti, the main vector of dengue, chikungunya, and Zika viruses in the Caribbean and Latin America. The development of novel vector management strategies is critical to reducing the transmission of its diseases. Piper spp., traditionally used for their culinary properties, have demonstrated insecticidal activity. The study explores extracts of Piper amalago var. amalago, a variety native to the Caribbean and Latin America, as insecticide synergists, compounds that are moderately toxic to insects but enhance toxicity when used in combination with synthetic insecticides. The toxicity of deltamethrin on field-collected Ae. aegypti using the CDC bottle bioassay was assessed. After confirming resistance, ethanol or hexane extracts were prepared from the aerial parts of Piper amalago var. amalago. The extracts were applied to subsequent lab-reared Ae. aegypti generations. Of the fractions prepared, the stem-ethanol extract was the most potent, with LD50 values of 0.007 mg/mg (plant extract/female Ae. aegypti body weight). The stem-ethanol extract demonstrated a synergistic effect with deltamethrin using a modified CDC bottle bioassay. Mortality increased from 22% ± 0.42 % with deltamethrin alone, at the dose of 10 µg active ingredient in 30 min to 96% ± 0.17 % with the application of stem-ethanol extract (LD25 = 2.2 μg/mg) followed by deltamethrin at the stated dose and time. GC-MS studies showed piperine to be the most abundant compound in the prepared extracts. The study demonstrates the use of Piper amalago var. amalago as an effective synergist against Ae. aegypti.