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Assessment of insecticidal responses of extracts and compounds of Drimys winteri, Lobelia tupa, Viola portalesia and Vestia foetida against the granary weevil Sitophilus granarius

Paz, Cristian, Burgos, Viviana, Iturra, Andres, Rebolledo, Ramón, Ortiz, Leandro, Baggio, Ricardo, Becerra, José, Cespedes-Acuña, Carlos L.
Industrial crops and products 2018 v.122 pp. 232-238
Drimys winteri, Lobelia, Sitophilus granarius, Solanaceae, Viola, active ingredients, botanical pesticides, chromatography, diet, flora, grains, insect pests, insecticidal properties, mortality, pest control, piperidine alkaloids, sesquiterpenoids, storage pests
Extracts and compounds from the Chilean plants canelo, Drimys winteri J.R. Forst. & G. Forst. (Winteraceae), tabaco del diablo, Lobelia tupa L. (Campanulaceae), huevil, Vestia foetida Hoffmans. (Solanaceae) and violeta, Viola portalesia Gay (Violaceae) were evaluated against Sitophilus granarius L. (Coleoptera: Curculionidae), one of the most widespread and destructive primary pests of stored cereals. Total extracts at concentrations of 2.5%w/w in diets, over 6-days, display insecticidal effects against S. granarius. D. winteri caused the mortality of 87.5% of insects; L. tupa 80%, V. foetida 56% whereas V. portalesia killed 45% of insects under the same conditions. In an effort to determine the active compounds, the extracts of Lobelia tupa and Drimys winteri were purified by preparative chromatography. The piperidine alkaloid lobelanidine was isolated from L. tupa and the drimane sesquiterpenes drimenin, drimenol and polygodial were isolated as the major components in the extract from D. winteri. The purified compounds compounds displayed insecticidal activity against S. granarius in a concentration/dependent-time manner (% mortality at 0.5%w/w over 6-days): polygodial 80%, drimenol 60%, lobelanidine 47%, and drimenin 20%. In agreement with these results, grains treated with polygodial showed greater protection against the feeding attack by the granary weevil. These results provide evidence of the importance of elements of the native Chilean flora as new potential sources of botanical pesticides for the insect pest control.