Synergistic toxicity of six compounds against two strains of the common bed bug Cimex lectularius

Cimex lectularius L., commonly known bed bug, is a difficult pest to control as it hides in cracks and crevices, and inside furniture. It comes out at night to feed upon human blood. To date reliance is on pesticides, typically the pyrethroids that led to insecticide resistance. Natural product-based compounds or their derivatives normally perform at the higher dose compared to the synthetic insecticides. But, this issue can be resolved by investigating synergistic combinations of natural products to reduce the dose rate, cost and increase the toxicity. Based on this, six compounds were selected for outperforming against the bed bugs in our inhouse studies. The individual toxicity, binary and trio combinations were studied against two strains of the bed bug (Bayonne ‘Insecticide-resistant’ and Ft. Dix strains ‘Susceptible’) in two different delivery methods: topical or fumigation. According to Wadley’s equation, the highly synergistic binary combinations in topical bioassay was a nethole - α-bisabolol. While, α-bisabolol showed synergies with three of the compounds. In fumigation bioassay, anethole-iso eugenol (χ² = 54.52) showed the highest synergy against Ft. Dix strain while eugenol-isoeugenol against the Bayonne strain.