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Pesticide Toxicology Laboratory

ISU Entomology / Pesticide Toxicology Laboratory / Insecticidal activity and biodegradation of the toxin from Bacillus thuringiensis subsp. kurstaki bound to humic acids from soil

Insecticidal activity and biodegradation of the toxin from Bacillus thuringiensis subsp. kurstaki bound to humic acids from soil

Authors: Crecchio, C., Stotzky, G.
Journal, Volume, Year: Soil Biology and Biochemistry, volume 30(4):463-470, 1998
Summary

Adsorption and binding of Btk toxin to humic acids (HA) extracted from two forest and two cultivated soils, biodegradation, and insecticidal activity of bound Btk toxin were evaluated. Adsorption of Btk toxins was faster to HAs from forest soils (1-2 h) than from cultivated soils (4-8 h). Differences in the amounts of Btk toxin bound to the different HAs after extensive washing with distilled water were primarily due to differences in total acidity and content of phenolic groups of the HAs. Adsorbed Btk toxin did not support microbial growth and was toxic to tobacco hornworm.

Comments

Additional research using natural soil and Btk from transgenic plant material also would more accurately determine ecological relevance. The Btk toxins used in this study were derived from Dipel technical powder. Insecticidal activity was determined by adding dilutions of bound and free Btk toxin onto tobacco hornworm medium. Although this shows the insecticidal activity, the ecological relevance was not established.