Transgenic Bt Cotton Does Not Disrupt the Top-Down Forces Regulating the Cotton Aphid in Central China

Abstract

Top-down force is referred to arthropod pest management delivered by the organisms from higher trophic levels. In the context of prevalent adoption of transgenic Bt crops that produce insecticidal Cry proteins derived from Bacillus thuringiensis (Bt), it still remains elusive whether the top-down forces are affected by the insect-resistant traits that introduced into the Bt crops. We explored how Bt cotton affect the strength of top-down forces via arthropod natural enemies in regulating a non-target pest species, the cotton aphid Aphis gossypii Glover, using a comparative approach (i.e. Bt cotton vs. conventional cotton) under field conditions. To determine top-down forces, we manipulated predation/parasitism exposure of the aphid to their natural enemies using exclusion cages. We found that the aphid population growth was strongly suppressed by the dominant natural enemies including Coccinellids, spiders and Aphidiines parasitoids. Coccinellids, spiders and the assemblage of other arthropod natural enemies (mainly lacewings and Hemipteran bugs) are similarly abundant in both plots, but with the parasitoid mummies less abundant in Bt cotton plots compared to the conventional cotton plots. However, the lower abundance of parasitoids in Bt cotton plots alone did not translate into differential top-down control on A. gossypii populations compared to conventional ones. Overall, the top-down forces were equally strong in both plots. We conclude that transgenic Bt cotton does not disrupt the top-down forces regulating the cotton aphid in central China.

Impact of transgenic soybean expressing Cry1Ac and Cry1F proteins on the non-target arthropod community associated with soybean in Brazil

“…The lack of insecticide effects in short-term studies of arthropod communities has also been detected in other ecosystems, particularly tropical agroecosystems [ 72 , 84 ], where the cultivation system itself usually exhibits a more prominent effect and may buffer the potential insecticide impact [ 79 – 81 , 85 ]. While Bt proteins are constitutively expressed in the crop throughout the growing season, there is a lack of significant short- and long-term impacts on arthropod assemblages, as reported for maize [ 15 , 66 ], cotton [ 35 , 47 , 78 , 86 ] and soybean [ 87 ]. Yu et al [ 87 ] reported non-significant impact of Bt -soybean, but using general faunistic indexes rather than multivariate analyses with higher taxonomic resolution.…”

Combined influence of Bt rice and rice dwarf virus on biological parameters of a non-target herbivore, Nephotettix cincticeps (Uhler) (Hemiptera: Cicadellidae)

“…Moreover, Han et al [ 48 ] assessed the current information related to the effects of insect-resistant GM crops on arthropod behavior and drew a conclusion that the majority of reports focused on behavior effects of target insects and the non-target herbivores were rarely affected. Longer egg duration and male adult longevity of the GRLHs on the testing RDV-infected Bt rice lines may slow their population growth, however, we noted that reduced population growth is not a general effect of GM crops [ 49 ]. Therefore, we conclude that growing Cry1C- and Cry2A-transgenic rice would pose a negligible risk to the GRLHs.…”

Species composition and richness of aphid parasitoid wasps in cotton fields in northern China

“…gossypii parasitoid communities in the cotton agroecosystems of northern China, reporting a total of three primary parasitoid species and 12 hyperparasitoids. Parasitoids are important natural enemies of cotton aphids in northern China 14 , 33 , with Lysiphlebia japonica widely assumed to be the dominant parasitoid species 18 , 21 , 23 – 29 . This parasitic wasp has been broadly studied in China, and applied research has quantified its impact on aphid population dynamics 33 , 34 , its oviposition behaviour and preferences in terms of host instar 35 and host plants 36 , and the effect of environmental conditions on its biological control efficacy 37 .…”

“…gossypii , parasitism rates tend to remain below 30% 17 – 21 . The dynamics of parasitoid wasp populations were only presented with the abundance of aphid mummies 22 , 23 , mummification rates 20 or Aphididae and hyperparasitoid proportions 18 . Cotton aphid parasitoids mainly belong to Aphidiinae (Braconidae) and Aphelinidae, with the former subfamily including Aphidius , Binodoxys , Lipolexis , Lysiphlebia , Lysiphlebus and Trioxys species.…”