NATURAL OCCURRENCE OF BACILLUS-THURINGIENSIS ON GRASS FOLIAGE

Bacillus thuringiensis isolates were naturally present on the phyllopl ane of grass foliage collected from a pasture field at Wageningen in T he Netherlands. Characterization of 32 isolates from foliage showed th at 75% belonged to serovar israelensis (H-14). A few other serovars we re also found (indiana, japonensis, nigeriensis and pakistani). In tox icity tests, 84% of the isolates showed larvicidal activity against Ae des aegypti, whereas no activity against Pieris brassicae was detected in any of the isolates. Activity against Tipula oleracea was document ed for a few isolates of serovar israelensis.