Biological characteristics of black armyworm Spodoptera cosmioides on genetically modified soybean and corn crops that express insecticide Cry proteins.

This study aimed to evaluate the development and reproduction of the black armyworm, Spodoptera cosmioides when larvae fed on leaves of Bt-corn hybrids, expressing a single Cry1F and also Cry1F, Cry1A.105 and Cry2Ab2 in pyramided corn and their non-Bt-isoline (hybrid 2B688), as well as on leaves of two soybean isolines expressing the Cry1Ac protein and its non-Bt isoline (A5547-227). We also assessed the effect of these Bt and non-Bt plants on the leaf consumption rate of S. cosmioides larvae. This pest was unable to develop when fed on any of the corn isolines (Bt and non-Bt). When both 1st and 3rd instar larvae were fed on corn leaf, mortality was 100% in both Bt and non-Bt corn. In contrast, when corn leaves were offered to 5th instar larvae, there were survivors. Defoliation and leaf consumption was higher with non-Bt corn than with both of the Bt corn isolines. There was no negative effect of Bt soybean leaves on the development and reproduction of S. cosmioides with respect to all evaluated parameters. Our study indicates that both Bt and non-Bt corn adversely affect the development of S. cosmioides while Bt soybean did not affect its biology, suggesting that this lepidopteran has major potential to become an important pest in Bt soybean crops.

Electrochemical and quantum chemical investigations of the insecticide fipronil.

This work describes an electrochemical and quantum chemical investigation of the fipronil insecticide. Cyclic voltammetry (CV) and square wave voltammetry (SWV) experiments were performed over a graphite-polyurethane (GPU) composite electrode. The fipronil molecule presents an one?electron irreversible oxidation reaction. Profiting the SWV signal a square wave stripping voltammetry (SWSV) procedure to determine the fipronil molecule in a 0.10 mol L-1 Britton-Robinson buffer solution, pH 8.0 was developed with accumulation potential and time of 0.50 V and 120 s, respectively. The limits of detection and quantification were 0.80 and 2.67 ?g L-1, respectively. Recovery tests were performed in three natural waters samples with values ranging from 99.67 to 101.37%. Quantum chemical studies showed that the nitrogen atom of the pyrazole group is the most probable oxidation site of the fipronil molecule.