Structure-activity relationships of 33 carboxamides as toxicants against female Aedes aegypti (Diptera: Culicidae).

Aedes aegypti L. is the primary vector of dengue and yellow fever viruses, and use of aerosolized insecticides is one of the primary ways to control this medically important mosquito. However, few new insecticides have been developed for mosquito control in recent years. As a part of our effort to search for new insecticides to control mosquitoes, toxicities of 33 carboxamides were evaluated against female A. aegypti by topical application. This group included nine different categories of compounds, namely benzamides, phenyl-propenamides, propanamides, butanamides, butenamides, pentanamides, pentenamides, hexanamides, and hexenamides, that exhibited varying levels of toxicity against this mosquito species. The most toxic compound tested was hexahydro-1-(1-oxohexyl)-1H-azepine, with a 24-h LD50 value of 0.4 microg per mosquito, whereas the most toxic compound at the LD95 level was N-ethyl-2-methyl-N-phenyl-benzamide (1.82 microg per mosquito). The least toxic compound was N,N-bis (2-methylpropyl)-3-phenyl-2-propenamide, with LD50 and LD95 values of 15.66 and 72.07 microg per mosquito, respectively. Results from this initial study may prove useful in guiding further carboxamide modifications for the development of potential new insecticides.