Antifeedant, insect growth regulatory and insecticidal effects of Calceolaria talcana (Calceolariaceae) on Drosophila melanogaster and Spodoptera frugiperda.
Extracts from Calceolaria talcana exhibited strong bioinsecticidal effects against Drosophila melanogaster and Spodoptera frugiperda. The most active extract was ethyl acetate and its majority compound verbascoside. The highest lethal concentration to the larvae of S. frugiperda and D. melanogaster was 20.0 µg/ml of the ethyl acetate extract with 95.8% and 67.0% of mortality, respectively. Against D. melanogaster the ethyl acetate extract showed the highest activity with 75.05% of antifeedant index at 25 µg/ml, methanol extract instead showed 100% to 100 µg/ml. At very low concentrations ethyl acetate and methanol extracts induce antifeedant and insect growth regulatory activity showing selective effects as deterrent and on the sclerotization showing a pre-emergence effect on S. frugiperda. The results from these extracts were better than showed by methanol extracts from Cedrela salvadorensis, Myrtillocactus geometrizans and Yucca periculosa samples used as positive controls.