Insect resistance to Bt crops: lessons from the first billion acres

Abstract

Evolution of resistance in pests can reduce the effectiveness of insecticidal proteins from Bacillus thuringiensis (Bt) produced by transgenic crops. We analyzed results of 77 studies from five continents reporting field monitoring data for resistance to Bt crops, empirical evaluation of factors affecting resistance or both. Although most pest populations remained susceptible, reduced efficacy of Bt crops caused by field-evolved resistance has been reported now for some populations of 5 of 13 major pest species examined, compared with resistant populations of only one pest species in 2005. Field outcomes support theoretical predictions that factors delaying resistance include recessive inheritance of resistance, low initial frequency of resistance alleles, abundant refuges of non-Bt host plants and two-toxin Bt crops deployed separately from one-toxin Bt crops. The results imply that proactive evaluation of the inheritance and initial frequency of resistance are useful for predicting the risk of resistance and improving strategies to sustain the effectiveness of Bt crops.

Understanding managers’ and scientists’ perspectives on opportunities to achieve more evolutionarily enlightened management in conservation

“…A key concern raised by evolutionary biologists is the general lack of consideration given by managers to how their management practices can act as a selection pressure on wild populations (Hendry et al., 2011; Smith et al., 2014). This is particularly relevant for invasive species management, where the evidence from agricultural science can inform risk assessments for management practice that might promote the evolution of resistance to the toxins used to control pest species (Neve, Busi, Renton, & Vila‐Aiub, 2014; Tabashnik, Brevault, & Carriere, 2013). Despite continued commentary about the long‐term implications of management actions that do not consider evolution (Carroll et al., 2014; Hoffmann & Sgrò, 2011; Smith et al., 2014), the reasons for this gap remain largely speculative.…”

Is a larger refuge always better? Dispersal and dose in pesticide resistance evolution

“…2011; Tabashnik et al. 2013). The applicability of this strategy has been promoted and questioned for different pest insect species, different crops, and different insecticides.…”

“…2011; Tabashnik et al. 2013). The theory assumes single locus resistance, and tracks resistance ( R ) allele frequencies and population density in two patches.…”

Lepidoptera (Insecta) associated with soybean in Argentina, Brazil, Chile and Uruguay

“…Another factor to be considered in the adoption of Bt technology is the risk of the development of resistance in populations of target pests (e.g. TABASHNIK, 2013;FARIAS et al, 2014). The Bt toxin is expressed in high dose in the plant, with high exposure and high persistence during the whole crop cycle.…”