ABSTRACT The constant use of chemical insecticides for Aedes aegypti control has caused resistance in the mosquito populations. Thus, the objective of this study was to analyze the larvicidal potential of extracts and fractions of plants on A. aegypti larvae. The analysis included sixty one extracts and twenty five fractions of fifty botanical species at concentrations of 0.25; 0.12; 0.06 to 0.03 mg mL-1; 4 replications and one negative control of dechlorinate water and 1% DMSO; and a positive control with rotenone. The toxicity index in descending order with LC50 for the most active of the extracts selected were ethanol extract of Ormosea arborea (0.111 mg mL-1) seeds and ethanol extracts of leaves such as Piper hispidum (0.169 mg mL-1), Solanum variabile (0.188 mg mL-1), O. arborea (0.238 mg mL-1), Turnera umifolia (0.242 mg mL-1) and Piper hispidum (0.567 mg mL-1). For plant fractions, the most active were chloroform (0.192 mg mL-1) and hexane (0.342 mg mL-1) P. aduncum leaves, hexane fraction (0.415 mg mL-1) and methanol extract (0.625 mg mL-1) of Spermacocea latifolia leaves. Regarding the extract of T. umifolia single species, there is no bibliographic report on their degree of efficiency as an insecticide.

Avaliou-se, em condições de laboratório, o efeito de diferentes concentrações (peso/volume) de extratos orgânicos (não aquosos) de folhas e ramos de Trichilia pallida Swartz em relação à lagarta-do-cartucho Spodoptera frugiperda (J. E. Smith). Inicialmente, foram testados os extratos acetônico e metanólico nas concentrações de 0,008 a 1% impregnados em folhas de milho, constatando-se, com base na mortalidade larval até os 10 dias, que os extratos acetônicos de folhas e de ramos e o extrato metanólico de ramos apresentaram maior atividade que o extrato metanólico de folhas. Empregando a mesma metodologia, foram testados os extratos acetato de etila e hexânico obtidos pela partição do extrato acetônico bruto, constatando-se que o extrato acetato de etila foi mais efetivo que o hexânico. Comparando-se os quatro solventes, a maior atividade tóxica dos extratos foi obtida com a utilização de acetona, seguindo-se metanol, acetato de etila e hexano.

The objective of this research was to evaluate the toxic activity of different concentrations (weight/volume) of organic extracts (non-aqueous) of leaves and twigs of Trichilia pallida Swartz on Spodoptera frugiperda (J. E. Smith) under laboratory conditions. Pieces of corn leaves were dipped in acetone solutions of T. pallida extracts at concentrations ranging from 0.008 to 1%. Larval mortality of S. frugiperda was evaluated during 10 days and acetone extracts of leaves and twigs and methanol extracts of twigs showed greater activity than methanol extract of leaves. Crude acetone extract was partitioned with hexane and ethyl acetate and evaluated by using the same methodology. Ethyl acetate fraction was more effective than hexane. Comparing the four solvents, the highest toxic activity of the extracts was obtained using acetone, followed by methanol, ethyl acetate and hexane.