Resistance Monitoring of <I>Helicoverpa armigera</I> (Lepidoptera: Noctuidae) to <I>Bacillus thuringiensis</I> Insecticidal Protein in China

Abstract

Sensitivities of Helicoverpa armigera (Hübner) field populations to Bacillus thuringiensis (Bt) insecticidal protein CrylAc were monitored during 1998-2000 in China. A total of 41 strains was sampled, and most of them were collected from Bt cotton planting regions. The range of IC50 values (concentration producing 50% inhibition of larval development to third instar) among different populations in 1998,1999, and 2000 were 0.020-0.105 microg/ml, 0.016-0.099 microg/ml, and 0.016-0.080 microg/ml, respectively. Diagnostic concentration studies (IC99) showed that the percentage of individuals reaching third instar ranged from 0 to 4.35%, with only eight of the 41 tested populations showing values above 0%. Also interesting was a trend over successive years in which fewer populations contained individuals that survived the diagnostic concentration by reaching third instar. Considering these data, it was determined that the field populations sampled during the 3-yr study were susceptible to CrylAc protein, and that movement toward resistance among H. armigera populations was not apparent.

Temporal allocation of metabolic tolerance to transgenic Bt cotton in beet armyworm, Spodoptera exigua (Hübner)

“…Since the first commercial release of GM crops expressing Bt genes, there have been environmental impact concerns. In particular, the continuous expression of the insecticidal protein in most tissues of the plant throughout the growing season has raised concerns regarding the development of resistance or tolerance in the target pest, and the possible impacts of this new pest control technology on various groups of non-target organisms of ecological and economic values [20,31,32]. Most herbivores are affected by the physiological and nutritional states of their host plants [33], such as cotton plants expressing Cry1Ac toxin.…”

Frequency of resistance to Vip3Aa20 toxin from Bacillus thuringiensis in Spodoptera frugiperda (Lepidoptera: Noctuidae) populations in Brazil

“…These methods were used for resistance monitoring of Bt toxins expressed on transgenic plants in several pest species, such as O. nubilalis (Siegfried et al, 2007), H. armigera (Wu et al, 2002), H. virescens (Sumerford et al, 1999;Albernaz et al, 2013), Helicoverpa zea (Boddie) (Sumerford et al, 1999), and S. frugiperda (Farias et al, 2014a).…”

Frequency and fitness cost of resistance to Bacillus thuringiensis in Chrysomela tremulae (Coleoptera: Chrysomelidae)

“…Among these factors, the frequency is certainly one of the most important: the lower the frequency, the more sustainable the strategy. The initial frequency of resistance has been estimated in only a limited number of cases, mostly in lepidopteran pests, due to practical limitations: Helicoverpa armigera (Wu et al, 2002), Heliothis virescens (Gould et al, 1997) and H. zea (Burd et al, 2003) on cotton, Ostrinia nubilalis on maize Bourguet et al, 2003), Scirpophaga incertulas (Bentur et al, 2000) on rice, and Pectinophora gossypiella (Tabashnik et al, 2000) on cotton. These studies yielded contrasting results, with the frequency of Bt resistance alleles ranging from 10 À4 to 10 À1 .…”