Lethal and Sublethal Effects of Leaves Extracts from Native and Exotic Plants in Southern Brazil against Spodoptera frugiperda (Lepidoptera: Noctuidae) Caterpillars

The caterpillar Spodoptera frugiperda is an important pest of several crops, due to the damage it causes and the difficulty of its control. The method of controlling these pests is through chemical insecticides, which cause adverse effects to the biotic and abiotic environment. The selection of new insecticides that meet the requirements of efficacy, safety, selectivity and those are economically viable, is highlighting the study of mechanisms of plant defense. The present study aimed to verify the insecticide effect of 27 plants in three different types of plants extracts: aqueous, decoction and polypeptide on S. frugiperda. Three plants were chosen for performing sublethal effects bioassays: two plants with the highest corrected mortality (E. pulcherrima and R. simsii) and the other plant (Maytenus ilicifolia (espinheira santa)) with corrected mortality similar to control. In preliminaries bioassays, 25 plants showed corrected mortality less than 50%, according to Abbott's formula. R. simsii (azalea) and E. pulcherrima (billed parrot) showed 51% and 68% of corrected mortality, respectively. Only R. simsii aqueous and the three extracts of E. pulcherrima differ significantly from control (P < 0.05). The aqueous extracts and decoction of R. simsii and polypeptide extract of E. pulcherrima reduced the larval period of S. frugiperda, different from control (P < 0.05). The polypeptide extract of R. simsii reduced the pupal period of the target insect. The extracts obtained by decoction, aqueous and polypeptide of E. pulcherrima extracts and decoction of polypeptides and R. simsii affected the fertility and fecundity of S. frugiperda. For the other parameters, there is no significant difference when compared with the control. The results of this study suggest that the extracts obtained by decoction, aqueous and polypeptide of E. pulcherrima and R. simsii can be used to control S. frugiperda. However, the successful search, product starting from extracts of plants depends on the availability of plant and the entire assembly around the detection of bioactive products, in addition to the active ingredients of the chemical synthesis and elucidation of the target site insecticide molecule.