Assessing the Effects of Bt Maize on the Predatory Mite Neoseiulus cucumeris

Abstract

The investigation of Neoseiulus cucumeris in the context of the ecological risk assessment of insect resistant transgenic plants is of particular interest as this omnivorous predatory mite species is commercially available and considered important for biological control. In a multitrophic feeding experiment we assessed the impact of Bt maize on the performance of N. cucumeris when offered spider mites (Tetranychus urticae) reared on Bt (Bt11, Syngenta) or non-Bt maize (near isogenic line) and Bt or non-Bt maize pollen as a food source. Various parameters including mortality, development time, oviposition rate were measured. Spider mites were used as a prey for N. cucumeris, since these herbivores are known to contain similar levels of Cry1Ab toxin, when reared on Bt maize, as those found in the transgenic leaf material. In contrast, toxin levels in pollen of this transgenic cultivar are very low. No differences in any of the parameters were found when N. cucumeris was fed with spider mites reared on Bt and non-Bt maize. Pollen was shown to be a less suitable food source for this predator as compared to spider mites. Moreover, subtle effects on female N. cucumeris (9% longer development time and 17% reduced fecundity) were measured when fed with pollen originating from Bt maize as compared to non-Bt maize pollen. Our findings indicate that the predatory mite N. cucumeris is not sensitive to the Cry1Ab toxin as no effects could be detected when offered Bt-containing spider mites, and that the effects found when fed with Bt maize pollen can be assigned to differences in nutritional quality of Bt and non-Bt maize pollen. The significance of these findings is discussed with regard to the ecological relevance for risk assessment of transgenic plants.

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

“…Estudos sobre as toxinas Cry presentes em plantas transgênicas sobre ácaros (herbívoros não-alvo), ainda são incipientes (Carter et al 2004, Rovenská et al 2005, Obrist et al 2006b, mas demonstraram que esses organismos geralmente não são afetados, apesar da grande exposição via aquisição e acúmulo da toxina em seu corpo, assim como encontrado neste estudo. Desta forma, podemos descartar a hipótese de um possível efeito negativo da toxina Cry1Ac ingerida e presente no corpo de T. urticae sobre o predador P. macropolis.…”

Expression of a barley cystatin gene in maize enhances resistance against phytophagous mites by altering their cysteine-proteases

“…Because of their short generation time and high population growth rates, mites have developed resistance to the major pesticide groups (Croft and Van de Baan 1988). In addition, no resistant plant cultivars are currently available, and phytophagous mites are not sensitive to toxins encoded by Bt genes (Rovenska et al 2005;Obrist et al 2006;Alvarez-Alfageme et al 2008;Li and Romeis 2010).…”

Effects of Transgenic Bt Cotton on the Population Density, Oviposition Behavior, Development, and Reproduction of a Nontarget Pest, <I>Adelphocoris suturalis</I> (Hemiptera: Miridae)

“…Most studies indicated that transgenic crops had no adverse effects on either Aphis gossypii or Adelphocoris suturalis (Lawo et al 2009;. Beneficial insects such as predatory mites (Obrist et al 2006;de Castro et al 2012), green lacewings (Chrysoperla carnea) (Romeis et al 2004;Li et al 2008) and beetles (Ferry et al 2007) were also unaffected. In contrast, some researchers observed high mortality rates among the larvae of ladybird beetle (Adalia bipunctata) reared on diets with Bt toxic protein (Hilbeck et al 2012).…”