Toxicity of Compounds Isolated from White Snakeroot (Ageratina altissima) to Adult and Larval Yellow Fever Mosquitoes (Aedes aegypti).

Botanicals have been the source for several classes of pesticides for mosquitoes. However, increasing resistance to these products and reduced numbers of choices necessitate the search for new active ingredients. Ageratina altissima (L.) King & H. Rob. or white snakeroot, is found throughout the eastern United States and contains known toxic compounds. We examine chromenes (benzopyrans) and benzofurans isolated fiom this plant for larvicidal and adulticidal activity against the dengue vector Aedes aegypti L. Initial activity identified several compounds that were effective against either larvae or adults. Interestingly, only two compounds were effective against both larva and adults. Dose curves were constructed from further testing of these active compounds to allow. comparative ranking of efficacy. We identified dehydrotremetone as the most effective larvicide (0.03 ± 0.001 ng/μL) and 6-acetyl-7-methoxy-2,2- dimethylchromene as the most effective adulticide (1.17 ± 0.31 μg/org) although other compounds were also active. This study provides additional useful data for evaluation of chromenes and benzofurans as possible mosquiticidal agents.