Toxic effects of Ricinus communis non-protein trypsin inhibitor on Spodoptera frugiperda (J. E. Smith) (Lepidoptera:Noctuidae)

Abstract

In the study reported herein, we aimed to isolate a trypsin inhibitor from Ricinus communis leaves through chromatographic and spectrometric techniques and evaluate its toxic effects on the development of Spodoptera frugiperda larvae. Plant extracts were submitted to fractionation in adsorption column. The fraction 10, which showed the highest inhibitory activity, were incorporated into an artificial diet at the concentrations of 0, 0.06, 0.12, 0.25 and 0.5%, and offered to S. frugiperda larvae. Fresh weight of larvae, food consumed and weight of eliminated faeces were registered. Based on these parameters the following nutritional index were calculated: Relative Consumption Rate (RCR), Relative Metabolic Rate (RMR), Relative Growth Rate (RGR), Approximated Digestibility (AD), Efficiency of Ingested Food Conversion (EIC), Efficiency of Digested Food Conversion (EDC) and the Metabolic Cost (100 - EDC). The inhibitor at 0.5% concentration was deleterious to S. frugiperda, extending the larval stage in 11 days, with higher RCR and ECD, and lower RGR, ECI and ECD. Therefore, the trypsin inhibitor from leaves of R. communis affected the S. frugiperda larval development, being promising in studies of alternative and sustainable control methods for lepidopteran pest species.

Keywords: Castor beans, enzymatic inhibition, integrated pest management, plant defense against herbivory