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Pesticide Toxicology Laboratory

ISU Entomology / Pesticide Toxicology Laboratory / Bacillus thuringiensis (Bt) toxin released from root exudates and biomass of Bt corn has no apparent effect on earthworms, nematodes, protozoa, bacteria, and fungi in soil

Bacillus thuringiensis (Bt) toxin released from root exudates and biomass of Bt corn has no apparent effect on earthworms, nematodes, protozoa, bacteria, and fungi in soil

Authors: Saxena, D., Stotzky, G.
Journal, Volume, Year: Soil Biology and Biochemistry, volume 33:1225-1230, 2001
Summary

The effects on earthworms (Lumbricus terrestris), nematodes, protozoa, and bacteria after 40 days in soil that had been planted with seeds of Bt corn (NK4640Bt) or isogenic Bt corn or in soil amended with leaves, stems and roots of Bt corn or isogenic non-Bt corn for 45 days was evaluated. No significant differences in mortality and weight of earthworms was observed in either exposure; however, Bt toxin was present in the gut of earthworms. There were also no significant differences in the colony-forming units of bacteria, nematodes, and protozoa.

Comments

One of the few studies that used natural soil and Bt toxin from transgenic plants. No effects on earthworm mortality or survival were observed, but reproductive effects were not evaluated. Growth may not be the best endpoint because the earthworms were already rather large (fully developed clitellum); newly hatched earthworms or juveniles would be more sensitive to a growth endpoint. The study only lasted 40 days, much shorter than the growing season of corn. Concentrations of Bt toxin in the soil were unknown, although larvicidal activity of the soil was determined using larvae of the tobacco hornworm.