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Pesticide Toxicology Laboratory

ISU Entomology / Pesticide Toxicology Laboratory / Immunological analysis of phloem sap of Bacillus thuringiensis corn and of the nontarget herbivore Rhopalosiphum padi (Homoptera: Aphididae) for the presence of Cry1Ab

Immunological analysis of phloem sap of Bacillus thuringiensis corn and of the nontarget herbivore Rhopalosiphum padi (Homoptera: Aphididae) for the presence of Cry1Ab

Authors: Raps, A., Kehr, J., Gugerli, P., Moars, W.J., Bigler, F., Hilbeck, A.
Journal, Volume, Year: Molecular Ecology, volume 10:525-533, 2001
Summary

Analyzed an aphid (Rhopalosiphum padi), the Egyptian cotton leafworm (Spodoptera littoralis), and excretions of both species for the presence of Cry1Ab Bt protein. Used N4640Bt and its isoline and also event 176. Also used a microcappillary and cut leaf exudation to collect phloem. Detection was performed with a plate-based ELISA. Pooled samples of insects or excretions were used for analysis. No Bt was found in phloem or in the honeydew of the aphids. One out of three trials led to a very low detection of Bt in the aphid. Both larvae and feces of the leafworm were positive for Bt and concentrations in feces were tenfold greater than those in the larvae. Fecal concentration was similar to plant levels.

Comments

Good study. Demonstrated that phloem feeders probably provide little trophic danger to predators. Also showed that leaf-feeding larvae can carry protein and excrete it in ELISA active form at near plant expression levels.