Persistence and nontarget effects of Bacillusthuringiensis in soil: a review

Abstract

This review presents information on the occurrence, persistence and nontarget effects of Bacillusthuringiensis Berliner (B.t.) in soil, with particular emphasis on forest ecosystems. Both field and laboratory studies have confirmed that B.t. is able to survive for several years after spraying, but studies on long-term persistence and possible accumulation of spores in soils are inadequate. The ecological role of B.t. in the soil ecosystem is poorly understood; we do not even know where and under what conditions B.t. multiplies in nature. Information on the effects of B.t. on soil microflora is contradictory, with studies variously suggesting that B.t. caused an increase, a decrease, or did not affect indigenous bacterial populations. Toxicity of B.t. to species of several invertebrate taxa (Acarina, Nematoda, Collembola, Annelida, Hymenoptera) inhabiting the soil has been demonstrated, but only rarely is it possible to relate dosage information to field situations, and in many cases the B.t. subspecies tested are not currently used for pest control in North America. There is an urgent need for further research to elucidate the relationships between B.t. and the natural soil microflora and fauna.