Different maize varieties have greater impact on Tetranychus urticae (Acari: Tetranychidae) than GE maize expressing Cry3Bb1 insecticidal protein

Abstract

Genetically engineered (GE) maize expressing Bacillus thuringiensis Cry3Bb1 protein was developed to control Diabrotica spp. (Coleoptera: Chrysomelidae). However, Cry proteins have been reported to have effects on non-target arthropods. We therefore investigated whether the non-target pest Tetranychus urticae (Acari: Tetranychidae) was negatively affected by GE maize expressing the insecticidal Cry3Bb1 protein. Five treatments were used in the laboratory tests to determine the life history parameters of T. urticae on leaves of field-grown maize varieties: (1) GE maize MON 88017, (2) isogenic maize, (3) isogenic maize protected with the soil applied insecticide chlorpyrifos (Dursban 10G), and two unrelated varieties (4) Kipous and (5) PR38N86. Newly emerged T. urticae larvae were individually released on the upper surface of leaf discs placed on water saturated cotton wool. Immatures and adults survival, duration of developmental stages and female fecundity were recorded daily until T. urticae died. Age-stage, two-sex life table method and test for trends, revealed no significant differences in 13 of 18 studied parameters. The unrelated varieties Kipous and PR38N86 on one side and maize with the same genetic background, namely GE maize and isogenic maize with or without insecticide protection, on the other side, showed significant variations in male longevity, larval survival rate, preoviposition period, and fecundity. In addition to the differences between varieties, GE maize and insecticide-protected isogenic maize showed a substantial difference in age-specific fecundity, but not in the mean number of eggs laid by females. The obtained results do not indicate that consumption of Cry3Bb1 has negative effect on T. urticae and suggest that GE maize does not pose a risk with respect to the non-target mite pest T. urticae. The results may have implications for the approval and renewal of import and cultivation for GE crop in the European Union.

Keywords: Cry3Bb1; GMO; Non-target effect; Risk assessment; Two-sex life-table; Two-spotted spider mite.