Sustained susceptibility of pink bollworm to Bt cotton in the United States

Abstract

Evolution of resistance by pests can reduce the benefits of transgenic crops that produce toxins from Bacillus thuringiensis (Bt) for insect control. One of the world's most important cotton pests, pink bollworm (Pectinophora gossypiella), has been targeted for control by transgenic cotton producing Bt toxin Cry1Ac in several countries for more than a decade. In China, the frequency of resistance to Cry1Ac has increased, but control failures have not been reported. In western India, pink bollworm resistance to Cry1Ac has caused widespread control failures of Bt cotton. By contrast, in the state of Arizona in the southwestern United States, monitoring data from bioassays and DNA screening demonstrate sustained susceptibility to Cry1Ac for 16 y. From 1996-2005, the main factors that delayed resistance in Arizona appear to be abundant refuges of non-Bt cotton, recessive inheritance of resistance, fitness costs associated with resistance and incomplete resistance. From 2006-2011, refuge abundance was greatly reduced in Arizona, while mass releases of sterile pink bollworm moths were made to delay resistance as part of a multi-tactic eradication program. Sustained susceptibility of pink bollworm to Bt cotton in Arizona has provided a cornerstone for the pink bollworm eradication program and for integrated pest management in cotton. Reduced insecticide use against pink bollworm and other cotton pests has yielded economic benefits for growers, as well as broad environmental and health benefits. We encourage increased efforts to combine Bt crops with other tactics in integrated pest management programs.

Alternative Splicing and Highly Variable Cadherin Transcripts Associated with Field-Evolved Resistance of Pink Bollworm to Bt Cotton in India

“…Unlike the situation in India, pink bollworm field populations in Arizona have remained susceptible to Cry1Ac despite more than 16 years of extensive exposure to Bt cotton producing this toxin [9], [43]–[44]. From 1996–2005, the main factors that delayed pink bollworm resistance in Arizona appear to be abundant refuges of non-Bt cotton, recessive inheritance of resistance, fitness costs associated with resistance and incomplete resistance [43], [44]. Since 2006, an eradication program using mass releases of sterile pink bollworm moths and other tactics in combination with up to 98% adoption of Bt cotton statewide has dramatically suppressed this pest in Arizona [9], [44].…”

Global range expansion of pest Lepidoptera requires socially acceptable solutions

“…The host species specificity of natural enemies on Lepidoptera needs to be demonstrated before release to avoid possible negative impacts on non-target arthropod species, or to avoid establishment of the parasitoid becoming a pest themselves (Munro and Henderson 2002). Biopesticides such as Bacillus thuringiensis kurstaki and baculoviruses can be made effective for some pests, although commercial availability, cost, efficacy and the evolution of resistance can be problematic (Glare and O'Callaghan 2000;Tabashnik et al 2012). Cultural controls such as sanitation can also be used as part of integrated pest management approaches where intensive field surveys may occur , although sanitation or host removal is only considered effective when integrated with other control tactics.…”

“…For codling moth, most of the recorded eradications were in Western Australia, and generally involved host destruction, requiring several years. Undoubtedly, the most impressive example of the integrated approach is the eradication of the pink bollworm, Pectinophora gossypiella Saunders (Lepidoptera: Gelechiidae) from the southern USA and northern Mexico using an AW-IPM approach that combined Bt cotton, sterile insect release and mating disruption (Tabashnik et al 2012). Other examples of successful AW-IPM programs that included a SIT/IS component include the eradication of the Australian painted apple moth, Teia anartoides Walker (Lepidoptera: Lymantriinae) from urban Auckland, New Zealand ) and C. cactorum from Isla Mujeres and Isla Contoy in Mexico (Bloem et al 2007a).…”

Genotype‐specific fitness cost of resistance to Bt toxin Cry1Ac in pink bollworm

“…Here, we expand upon the second approach and use it to estimate the overall effect of costs of resistance to Cry1Ac on specific genotypes of the pink bollworm. This invasive pest was the primary target of Bt cotton in Arizona before its virtual eradication by a multi‐tactic program that included mass releases of sterile moths and planting of nearly 100% Bt cotton . Previous studies have shown that fitness costs associated with pink bollworm resistance to Cry1Ac affect development time, growth rate, larval survival, overwintering survival, paternity, and sperm transfer .…”

“…This invasive pest was the primary target of Bt cotton in Arizona 26-28 before its virtual eradication by a multi-tactic program that included mass releases of sterile moths and planting of nearly 100% Bt cotton. 29,30 Previous studies have shown that fitness costs associated with pink bollworm resistance to Cry1Ac affect development time, growth rate, larval survival, overwintering survival, paternity, and sperm transfer. [31][32][33][34][35][36] The fitness costs identified in these studies were generally recessive, although the cotton defensive phytochemical gossypol induced larger and less-recessive costs affecting larval survival and growth rate.…”