Insecticidal activity of the toxins from Bacillus thuringiensis subspecies kurstaki and tenebrionis adsorbed and bound on pure and soil clays
Authors: Tapp, H., Stotzky, G.
Journal, Volume, Year: Applied and Environmental Microbiology, volume 61(5):1786-1790, 1995
Btk and Btt toxins were bound on montmorillonite (M), kaolinite (K), and the clay size fraction of Kitchawan soil. All samples containing Btk toxins were toxic to tobacco hornworm larvae. Greater amounts of Btk were bound to M than K, but LC50 values were not significantly different. All samples containing Btt toxins were toxic to Colorado potato beetle larvae. Btt toxin bound on M had a significantly higher LC50 than free or adsorbed (30% of Btt was desorbed by washings with distilled water) toxin. Results for the clay-size fraction were similar to those found for the pure clays.
The Btk toxins used in this study were derived from Dipel, and Btt toxins were derived from M-One (Mycogen Corp.). Experiments used pure montmorillonite and kaolinite in addition to the clay size fraction isolated from Kitchawan soil. Natural soils and were not tested; also, Bt toxins derived from transgenic crops were not studied.