No abstract

Insecticides derived from the bacterium Bacillus thuringiensis (Bt) and plants genetically modified (GM) to express B. thuringiensis toxins are important alternatives for insect pest control worldwide. Risk assessment of B. thuringiensis toxins to non-target organisms has been extensively studied but few toxicological tests have considered soil invertebrates. Oribatid mites are one of the most diverse and abundant arthropod groups in the upper layers of soil and litter in natural and agricultural systems. These mites are exposed to the toxic compounds of GM crops or pesticides mainly when they feed on vegetal products incorporated in the soil. Although some effects of B. thuringiensis products on Acari have been reported, effects on oribatid mites are still unknown. This study investigated the effects of the ingestion of Bt cotton Bollgard and of the B. thuringiensis commercial product Dipel WP on the pantropical species Scheloribates praeincisus (Scheloribatidae). Ingestion of Bollgard and Dipel did not affect adult and immature survivorship and food consumption (estimated by number of fecal pellets produced daily) or developmental time of immature stages of S. praeincisus. These results indicate the safety of Bollgard and Dipel to S. praeincisus under field conditions where exposition is lower and other food sources besides leaves of Bt plants are available. The method for toxicological tests described here can be adapted to other species of Oribatida, consisting on a new option to risk assessment studies.

No abstract

Agro-industrial residues and by-products available in southeastern Brazil were used as ingredients for low-cost culture media for liquid fermentation of Bacillus thuringiensis var. kurstaki. Highest spore yield was obtained with a medium containing cheese whey, soya bean milk and mofasses (WSM). Crystals and spores were produced in ali media and potency o f the final product was highest for nutrient broth + yeast extract medium (N B Y). There was no correlation between the number of spores in the fermented media and the potency of the preparations. Considering ali three factors, the potencies, costs and yields of the final products, lowest relative cost was obtained with BM M medi um (Bombyx mo ri pupae + mo/asses). NBY and WSM had intermediate relative cost approximately nine times higher than BMM. The cost analysis suggests that BMM medium should be preferred for local production o f B. thuringiensis var. kurstaki in comparison to other media tested. The results ais o demonstrate the importance o f considering yields, cost and potency o f the B. thuringiensis preparations in selecting the production medium.

Problem formulation is the formal opening stage of a risk assessment that determines its purpose and scope and hence guides the gathering of information data. The concepts of familiarity and history of safe use are an integral part of problem formulation. These concepts do not replace the case-by-case approach and are not taken as safety standards but are valuable components of the process that shape the generation of plausible, testable risk hypotheses. The International Life Sciences Institutes in Brazil and Argentina have facilitated numerous discussions on the scientific principles for risk assessment of transgenic crops in the Latin American region in the past 5-6 years. The session held at ISBR 15th elaborated on the familiarity concept and derived tools and their role in the evolution of risk evaluation criteria. Examples of how different countries in the Americas interpret and apply these conceptual tools show that familiarity is a valuable concept, although terms are very often confused and vaguely defined. Formalizing these terms with clear definitions and scope of application in guidelines and regulatory documents would reduce ambiguity, enhance predictability, and add transparency to the evaluation processes.