The influence of different maize varieties and treatments on the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)
Abstract: Laboratory experiments were carried out to assess the life-table parameters of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae) on leaves of four maize varieties: (1) transgenic Bt maize variety MON 88017 expressing Cry3Bb1 for control of Diabrotica spp., and protein CP4 EPSPS for a toleration of glyphosate-based herbicides, (2) isogenic variety treated with or without soil insecticide, (3) KIPOUS and (4) PR38N86. The latter two maize varieties were used as independent references. The leaves used in the experiments were collected in the field after flowering. The content of Cry protein was verified with an immunological ELISA test. Newly emerged larvae were individually placed on the upper surface of leaf discs placed on water saturated cotton in plastic Petri dishes. Survival of juveniles, developmental time and female fecundity was examined daily until the mites died. The longevity of adults was the longest and females oviposited the highest amount of eggs on Bt maize though not significantly different from spider mites reared on the isogenic variety. Similarly, no statistically significant differences between mites reared on the Bt variety and those reared on the isogenic variety were found in life table parameters. On the other hand, life table parameters of T. urticae on the soil insecticide-treated isogenic variety were significantly worse compared to those on the other varieties. We can thus conclude that the obtained results do not indicate any significant effect of the Cry3Bb1 toxin on measured life table parameters of T. urticae.