Toxicological evaluation of genetically modified cotton (Bollgard®) and Dipel® WP on the non-target soil mite Scheloribates praeincisus (Acari: Oribatida)

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.

Biologia comparada e comportamento de Tetranychus urticae Koch (Acari: Tetranychidae) e Phytoseiulus macropilis (Banks) (Acari: Phytoseiidae) em algodoeiro bollgardTM e Isolinha não-Transgênica

“…A ausência de efeito do milho Bt, que expressa a toxina Cry1Ab, foi também observado por Dutton et al (2003). O mesmo ocorreu com a toxina Cry1Ac presente no algodão Bollgard TM sobre o desenvolvimento dos estágios imaturos, sobrevivência de adultos e imaturos e o consumo alimentar (estimado pelo número de peletes fecais) de Scheloribates praeincisus (Berlese) (Acari: Oribatida) (Oliveira et al 2007b). Rhizoglypus robini (Claparède) (Acari: Acaridae) também não foi afetada pela toxina Cry3Bb1 presente no milho Bt, em relação à sobrevivência de adultos e imaturos coletados em armadilhas no milho Bt e em quatro isolinhas não-Bt (Carter et al 2004).…”

Ocorrência do ácaro fitófago Catarhinus tricholaenae Keifer (Acari: Diptilomiopidae) em cultivares de milho Bt

“…Foram estudados os efeitos de inibidores de protease em soja e de algodão geneticamente modificado sobre a espécie do ácaro de solo Scheloribates praeincisus (Acari: Oribatida). Os resultados mostraram que as referidas defesas das plantas não afetaram os parâmetros biológicos avaliados para a espécie S. praeincisus, sendo inócuo para esse organismo não alvo (OLIVEIRA et al, 2007;SIMÕES et al, 2008).…”

Effects of soybean proteinase inhibitors on development of the soil mite Scheloribates praeincisus (Acari: Oribatida)

“…25 mm high, 22 mm diameter) lined in ca. 3/4 of its volume with a 9:1 mixture of plaster-of-Paris (Yellow dental plaster type III, Pasom Indústria e Comércio de Materiais Odontológicos Ltda., São Paulo, Brazil) and activated vegetal charcoal (powder) as described in Oliveira et al (2007). Rearing chambers were placed inside a humid chamber (10 cm high, 20 cm diameter) hermetically locked, containing a saturated solution of KH 2 PO 4 to maintain 96% relative humidity.…”

“…Test chambers were similar to rearing chambers but smaller. They were made from 0.5-ml microtube (Eppendorf) as described in Oliveira et al (2007). Larval eclosion marked the beginning of evaluations.…”

“…They fed Oppia nitens Koch (Oribatida: Oppiidae) on leaves of Bt-cotton and Bt-potato and did not Wnd any eVects on population growth of adults and nymphs. Recently, the eVects of the ingestion of Bt cotton Bollgard ® on the soil mite Scheloribates praeincisus (Berlese) (Scheloribatidae) was evaluated (Oliveira et al 2007); ingestion of Bollgard did not aVect adult and immature survivorship and food consumption or developmental time of immature stages of S. praeincisus, thus indicating the safety of Bollgard to S. praeincisus.…”