Susceptibility of non-target invertebrates to Brazilian microbial pest control agents.

Microbial pest control agents or entomopathogens have been considered an interesting alternative to use instead of chemical insecticides. Knowledge of ecotoxicity data is very important to predict the hazard of any product released in the environment and subsidize the regulation of these products by governmental agencies. In the present study four new Brazilian strains of Bacillus and one fungus were tested to evaluate their acute toxicity to the microcrustacean Daphnia similis, the snail Biomphalaria glabrata and the dung beetle Digitonthophagus gazella. The microcrustaceans and the snails were exposed to entomopathogens in synthetic softwater and the beetles were exposed directly in cattle dung. Obtained data reveal low susceptibility of the non-target species to tested microorganisms, with lethal concentrations being observed only at much higher concentrations than that effective against target insects. These results show that the tested strains are selective in their action mode and seem to be non-hazardous to non-target species.

Acute toxicity and cytotoxicity of Bacillus thuringiensis and Bacillus sphaericus strains on fish and mouse bone marrow.

The insecticidal properties of delta-endotoxins from Bacillus thuringiensis (Bt) serotypes kurstaki and israelensis and crystal proteins of Bacillus sphaericus (Bs) serotype H5 have been used in insect control for decades. The availability of microbial toxins in biopesticides as well as in plants with incorporated protection has been increasing the concerns about biosafety. Acute toxicity to Danio rerio and cytotoxicity on mouse bone marrow cells and peripheral erythrocytes of Oreochromis niloticus were tested with Bt israelensis, Bt kurstaki and Bs H5 strains. The concentration and dose tested were 10(6) and 10(8) spores/ml, respectively. Neither lethality nor effects on mouse bone marrow were promoted by any strain. In necrosis-apoptosis study on peripheral erythrocytes of O. niloticus an increased frequency of necrotic cells caused by exposure to strains of B. thuringiensis was found. Exposure to B. sphaericus did not show cytotoxic effects in either tested system. None of the strains studied induced apoptosis in contrast with the chemical controls.