The role of octopamine receptor agonists in the synergistic toxicity of certain insect growth regulators (IGRs) in controlling Dengue vector Aedes aegypti (Diptera: Culicidae) mosquito

• Pyriproxyfen was the most potent IGR insecticide among the tested insecticides based on the IGR assay.
• Diafenthiuron was the most potent lethal insecticide among the Tested IGR according to the lethal toxicity assay.
• Amitraz is a promising tool in increasing the potency of the selected insecticides controlling Aedes aegypti mosquito.

The synergistic action of octopamine receptor agonists (OR agonists) on many insecticide classes (e.g., organophosphorus, pyrethroids, and neonicotinoids) on Aedes aegypti L. has been reported recently. An investigation of OR agonist’s effect on insect growth regulators (IGRs) was undertaken to provide a better understanding of the mechanism of action. Based on the IGR bioassay, pyriproxyfen was the most potent IGR insecticide tested (EC50 = 0.0019 ng/ml). However, the lethal toxicity results indicate that diafenthiuron was the most potent insecticide (LC50 = 56 ng/cm2) on A. aegypti adults after 24 h of exposure. The same trend was true after 48 and 72 h of exposure. Further, the synergistic effects of OR agonists plus amitraz (AMZ) or chlordimeform (CDM) was significant on adults. Among the tested synergists, AMZ increased the potency of the selected IGRs on adults the greatest. As results, OR agonists were largely synergistic with the selected IGRs. OR agonists enhanced the lethal toxicity of IGRs, which is a valuable new tool in the field of A. aegypti control. However, further field experiments need to be done to understand the unique potential role of OR agonists and their synergistic action on IGRs.

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