Farm-scale evaluation of the impacts of transgenic cotton on biodiversity, pesticide use, and yield

Abstract

Higher yields and reduced pesticide impacts are needed to mitigate the effects of agricultural intensification. A 2-year farm-scale evaluation of 81 commercial fields in Arizona show that use of transgenic Bacillus thuringiensis (Bt) cotton reduced insecticide use, whereas transgenic cotton with Bt protein and herbicide resistance (BtHr) did not affect herbicide use. Transgenic cotton had higher yield than nontransgenic cotton for any given number of insecticide applications. However, nontransgenic, Bt and BtHr cotton had similar yields overall, largely because higher insecticide use with nontransgenic cotton improved control of key pests. Unlike Bt and BtHr cotton, insecticides reduced the diversity of nontarget insects. Several other agronomic and ecological factors also affected biodiversity. Nevertheless, pairwise comparisons of diversity of nontarget insects in cotton fields with diversity in adjacent noncultivated sites revealed similar effects of cultivation of transgenic and nontransgenic cotton on biodiversity. The results indicate that impacts of agricultural intensification can be reduced when replacement of broad-spectrum insecticides by narrow-spectrum Bt crops does not reduce control of pests not affected by Bt crops.agricultural sustainability ͉ environmental impact ͉ transgenic crops T he increasing world population and changes in consumption patterns may necessitate significant agricultural intensification in the next 50 years (1, 2). Unless crop yield is improved and release of fertilizers and pesticides from croplands is reduced, such intensification could augment contamination and perturbation of managed and natural ecosystems, ultimately harming biodiversity and public health (1-4). It was proposed that transgenic Bacillus thuringiensis (Bt) crops could be valuable tools for increasing agricultural productivity while minimizing the environmental impacts of agriculture (1, 2). However, the potential effects of transgenic crops on nontarget arthropods have caused concern, especially in regions where agricultural land is important to sustain biodiversity (5-7).Although Bt crops are grown extensively worldwide (8), no large-scale studies had been performed to simultaneously test whether they have favorable agricultural effects and minimal impacts on nontarget arthropods. Here, we report results of a 2-year farm-scale evaluation of the effects of transgenic cotton on biodiversity, pesticide use, and yield. We studied 81 commercial fields in a region of 6,600 km 2 in Arizona, where Bt cotton represented 48% and 62% of the cotton planted in the first and second year of the study, respectively. Forty fields were planted to nontransgenic (nonTr) cotton, 21 fields to transgenic cotton producing the Bt toxin Cry1Ac (Bt), and 20 fields to cotton with Bt protein and herbicide resistance (BtHr). Bt cotton with Cry1Ac controls the pink bollworm (Pectinophora gossypiella), a major insect pest of cotton (9, 10). Results and DiscussionEffects of Transgenic Cotton on Pesticide Use. Transgenic cotton was treate...

Susceptibility of Cry1Ab maize-resistant and -susceptible strains of sugarcane borer (Lepidoptera: Crambidae) to four individual Cry proteins

“…Transgenic insect-resistant crops expressing Bacillus thuringiensis (Bt) proteins have been used successfully for insect management worldwide since they were first commercialized in 1996 (Cattaneo et al, 2006;Wu et al, 2008;Hutchison et al, 2010;James, 2011). However, as Bt maize provides unprecedented control of some caterpillar pests through a simple seed choice, the widespread use of Bt crops could also accelerate development of resistance in target pest populations.…”

Boundaries of sustainability in simple and elaborate models of agricultural pest control with a pesticide and a non-toxic refuge

“…Tens of millions of hectares of Bt maize and cotton were planted in 2009, and future increases are expected [21]. The use of such transgenic plants has the potential to reduce the need for sprayed pesticides [14], which run off into the environment and pose dangers for farm workers [11].…”

Field-evolved resistance by western corn rootworm to multipleBacillus thuringiensistoxins in transgenic maize

“…Most of this area was planted in Bt cotton and Bt maize (1). Benefits of Bt crops include effective management of target pests, decreased use of conventional insecticides, and reduced harm to nontarget organisms (2)(3)(4)(5). However, the evolution of resistance could diminish these benefits.…”