scholarly journals Effectiveness of the natural resistance management refuge for Bt-cotton is dominated by local abundance of soybean and maize

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Benjamin Arends ◽  
Dominic D. Reisig ◽  
Shawnee Gundry ◽  
Anders S. Huseth ◽  
Francis P. F. Reay-Jones ◽  
...  
Keyword(s):  
Environmental Protection Agency ◽  
Helicoverpa Zea ◽  
Resistance Management ◽  
Management Plan ◽  
Genetically Engineered ◽  
Natural Resistance ◽  
Bt Cotton ◽  
Cotton Production ◽  
Insect Management ◽  
Management Measures

AbstractGenetically engineered crops expressing Bacillus thuringiensis (Bt) Cry toxins have transformed insect management in maize and cotton, reducing insecticide use and associated off-target effects. To mitigate the risk that pests evolve resistance to Bt crops, the US Environmental Protection Agency requires resistance management measures. The approved resistance management plan for Bt maize in cotton production regions requires a structured refuge of non-Bt maize equal to 20% of the maize planted; that for Bt cotton relies on the presence of an unstructured natural refuge comprising both non-Bt crop and non-crop hosts. We examined how abundance of Bt crops (cotton and maize) and an important non-Bt crop (soybean) component of the natural refuge affect resistance to Bt Cry1Ac toxin in local populations of Helicoverpa zea, an important lepidopteran pest impacted by Bt cotton and maize. We show refuge effectiveness is responsive to local abundances of maize and cotton and non-Bt soybean, and maize, in its role as a source of H. zea infesting cotton and non-Bt hosts, influences refuge effectiveness. These findings have important implications for commercial and regulatory decisions regarding deployment of Bt toxins targeting H. zea in maize, cotton, and other crops and for assumptions regarding efficacy of natural refuges.

Do the plant host origins of Helicoverpa (Lepidoptera: Noctuidae) moth populations reflect the agricultural landscapes within which they are caught?

2018 ◽  
Vol 109 (1) ◽  
pp. 1-14
Author(s):  
G.H. Baker ◽  
C.R. Tann ◽  
P. Verwey ◽  
L. Lisle
Keyword(s):  
Spatial Scales ◽  
Resistance Management ◽  
Pigeon Pea ◽  
Management Plan ◽  
Agricultural Landscapes ◽  
Bt Cotton ◽  
Cotton Production ◽  
Plant Host ◽  
Multiple Regions ◽  
Cotton Farmers

AbstractThe use of Bt cotton varieties has greatly reduced the amount of conventional insecticides required to control lepidopteran pests, Helicoverpa armigera and Helicoverpa punctigera, in Australia, but the possibility that these moths might become resistant to Bt remains a threat. Consequently, a Resistance Management Plan, which includes the mandatory growing of refuge crops (pigeon pea and non-Bt cotton; both C3 plants), has been established for Bt cotton farmers. However, knowledge of the relative contributions made to overall moth populations from the many host origins (both C3 and C4 plants) available to these insects throughout cotton production regions remains limited, as do the scales of movement and spatial mixing of moths within and between these areas. This study used stable isotope signatures (in particular δ13C) to help identify where moths fed as larvae within separate cotton production regions which differed in their proportions of C3 and C4 host crops (e.g. cotton and sorghum, respectively). C3-derived moths predominated in the early season, but C4-derived moths increased in frequency later. The overall proportion of C4 moths was higher in H. armigera than in H. punctigera. Whilst the relative proportions of C3 and C4 moths differed between regions, no differences in such proportiorns were found at smaller spatial scales, nor were there significant correlations between crop composition and isotope signatures in moths. Overall, these results suggest that C4 host plants are likely to be very important in offsetting the development of Bt resistance in these insects and such influences may operate across multiple regions within a single growing season.

Helicoverpa zea (Lepidoptera: Noctuidae) Preference for Plant Structures, and Their Location, Within Bt Cotton Under Different Nitrogen and Irrigation Regimes

2019 ◽  
Vol 112 (4) ◽  
pp. 1741-1751
Author(s):  
Lewis R Braswell ◽  
Dominic D Reisig ◽  
Clyde E Sorenson ◽  
Guy D Collins
Keyword(s):  
Helicoverpa Zea ◽  
Resistance Management ◽  
Larval Feeding ◽  
Bt Cotton ◽  
Larval Distribution ◽  
Cotton Plants ◽  
Small Plot ◽  
Nitrogen Treatments ◽  
Behavioral Resistance ◽  
Lepidoptera Noctuidae

Abstract Helicoverpa zea Boddie is a common economic pest of cotton (Gossypium hirsutum L.), including transgenic cotton varieties that express Bacillus thuringiensis (Bt). Helicoverpa zea oviposition is similar in Bt and non-Bt cotton, but behavior of H. zea larvae can be different in the presence of Bt, with neonates moving away from terminals faster in single-toxin Bt than non-Bt cotton or avoiding Bt-treated diet in the lab. We quantified H. zea oviposition and larval distribution on structures within cotton plants in small plot experiments of Cry1Ac + Cry1F cotton for 2 yr under different irrigation and nitrogen treatments. More eggs were oviposited on plants receiving nitrogen application during 2016 and on leaves in the top section of irrigated plants during 2017, but other treatment effects on eggs or larvae were minimal. Helicoverpa zea eggs were most common on leaves in the top third of plants at position zero and middle section of cotton plants throughout the season, but some oviposition occurred on fruiting structures as well. First and second instars were more common on squares in the top section of plants during 2016 and bolls in the middle and lower sections during 2017 due to oviposition lower in the canopy during 2017. During both years, third through fifth instars were more common on bolls in the middle and lower section of plants closer to the main stem. These findings have resistance management implications as extended larval feeding on bolls could optimize nutrition, decrease Bt susceptibility, and potentially influence behavioral resistance.

scholarly journals Hybridizing transgenic Bt cotton with non-Bt cotton counters resistance in pink bollworm

2017 ◽  
Vol 114 (21) ◽  
pp. 5413-5418 ◽  
Author(s):  
Peng Wan ◽  
Dong Xu ◽  
Shengbo Cong ◽  
Yuying Jiang ◽  
Yunxin Huang ◽  
...  
Keyword(s):  
First Generation ◽  
Resistance Management ◽  
Genetically Engineered ◽  
Pink Bollworm ◽  
Bt Cotton ◽  
Bt Toxin ◽  
Random Mixture ◽  
Cotton Plants ◽  
Evolution Of Resistance ◽  
Insecticide Sprays

Extensive cultivation of crops genetically engineered to produce insecticidal proteins from the bacteriumBacillus thuringiensis(Bt) has suppressed some major pests, reduced insecticide sprays, enhanced pest control by natural enemies, and increased grower profits. However, these benefits are being eroded by evolution of resistance in pests. We report a strategy for combating resistance by crossing transgenic Bt plants with conventional non-Bt plants and then crossing the resulting first-generation (F1) hybrid progeny and sowing the second-generation (F2) seeds. This strategy yields a random mixture within fields of three-quarters of plants that produce Bt toxin and one-quarter that does not. We hypothesized that the non-Bt plants in this mixture promote survival of susceptible insects, thereby delaying evolution of resistance. To test this hypothesis, we compared predictions from computer modeling with data monitoring pink bollworm (Pectinophora gossypiella) resistance to Bt toxin Cry1Ac produced by transgenic cotton in an 11-y study at 17 field sites in six provinces of China. The frequency of resistant individuals in the field increased before this strategy was widely deployed and then declined after its widespread adoption boosted the percentage of non-Bt cotton plants in the region. The correspondence between the predicted and observed outcomes implies that this strategy countered evolution of resistance. Despite the increased percentage of non-Bt cotton, suppression of pink bollworm was sustained. Unlike other resistance management tactics that require regulatory intervention, growers adopted this strategy voluntarily, apparently because of advantages that may include better performance as well as lower costs for seeds and insecticides.

scholarly journals How do "imagined farmers" negotiate actual risks? Biosafety trade-offs in Bt cotton production in Andhra Pradesh, India

2012 ◽  
Vol 19 (1) ◽  
pp. 162
Author(s):  
Julia Freeman
Keyword(s):  
Political Ecology ◽  
Andhra Pradesh ◽  
Qualitative Interviews ◽  
Environmental Safety ◽  
Genetically Engineered ◽  
Bt Cotton ◽  
Unintended Effects ◽  
Cotton Production ◽  
Trade Offs ◽  
Vantage Points

India's encounter with genetically engineered Bt cotton has been a contested one, and one that has rarely conformed to expectations. I argue that two primary vantage points on the question of agricultural biotechnology – those advocating the "biosafe use" of Bt cotton or those who insist it involves "inherent problems" - frequently anticipate an "imagined farmer" in incomplete and sometimes plainly incorrect ways. Thus, there is more to the Bt cotton debate than has been considered to date. Drawing from qualitative interviews with cotton farmers in two regions of Andhra Pradesh, I call attention to the unintended effects of widespread Bt cotton cultivation and debates missing from this controversy. Misconstrual of the "imagined farmer" has edged out civil society's acknowledgement of farmers' negotiation of the (immediate and physical) risks of pesticide use as contrasted with those (more abstracted and unknown) of genetically engineered seed. Bt cotton's advocates, on the other hand, seldom address the unintended effects of its widespread use, including potentially reduced labor opportunities for the most marginal rural laborers. In conclusion, I urge a more expansive assessment of the trade-offs between risks and benefits that farmers make regarding Bt cotton, alongside a closer look at the nuances of their decision-making. Framing agribiotech risk as a matter of manageable (or inherently problematic) "biosafety" does not resonate with farmers using a broader concept of health and environmental safety threatened by heavy pesticide usage.Keywords: Bt cotton, political ecology, genetic engineering risk, pesticides, India

scholarly journals Sweet Corn Sentinel Monitoring for Lepidopteran Field-Evolved Resistance to Bt Toxins

2020 ◽  
Author(s):  
G P Dively ◽  
T P Kuhar ◽  
S Taylor ◽  
H B Doughty ◽  
K Holmstrom ◽  
...  
Keyword(s):  
Helicoverpa Zea ◽  
Sweet Corn ◽  
Resistance Management ◽  
Management Plan ◽  
Bt Crops ◽  
Phenotypic Resistance ◽  
Bt Toxins ◽  
Field Efficacy ◽  
Canadian Provinces ◽  
Bt Crop

Abstract As part of an insect resistance management plan to preserve Bt transgenic technology, annual monitoring of target pests is mandated to detect susceptibility changes to Bt toxins. Currently Helicoverpa zea (Boddie) monitoring involves investigating unexpected injury in Bt crop fields and collecting larvae from non-Bt host plants for laboratory diet bioassays to determine mortality responses to diagnostic concentrations of Bt toxins. To date, this monitoring approach has not detected any significant change from the known range of baseline susceptibility to Bt toxins, yet practical field-evolved resistance in H. zea populations and numerous occurrences of unexpected injury occur in Bt crops. In this study, we implemented a network of 73 sentinel sweet corn trials, spanning 16 U.S. states and 4 Canadian provinces, for monitoring changes in H. zea susceptibility to Cry and Vip3A toxins by measuring differences in ear damage and larval infestations between isogenic pairs of non-Bt and Bt hybrids over three years. This approach can monitor susceptibility changes and regional differences in other ear-feeding lepidopteran pests. Temporal changes in the field efficacy of each toxin were evidenced by comparing our current results with earlier published studies, including baseline data for each Bt trait when first commercialized. Changes in amount of ear damage showed significant increases in H. zea resistance to Cry toxins and possibly lower susceptibility to Vip3a. Our findings demonstrate that the sentinel plot approach as an in-field screen can effectively monitor phenotypic resistance and document field-evolved resistance in target pest populations, improving resistance monitoring for Bt crops.

scholarly journals Development of Economic Thresholds Toward Bollworm (Lepidoptera: Noctuidae), Management in Bt Cotton, and Assessment of the Benefits From Treating Bt Cotton With Insecticide

2021 ◽  
Author(s):  
Wilfrid Calvin ◽  
Fei Yang ◽  
Sebe A Brown ◽  
Angus L Catchot ◽  
Whitney D Crow ◽  
...  
Keyword(s):  
Helicoverpa Zea ◽  
Field Experiments ◽  
Management Program ◽  
Bt Cotton ◽  
Cotton Production ◽  
Economic Injury Level ◽  
Insecticide Application ◽  
Yield Increase ◽  
Injury Threshold ◽  
Economic Thresholds

Abstract Widespread field-evolved resistance of bollworm [Helicoverpa zea (Boddie)] to Cry1 and Cry2 Bt proteins has threatened the utility of Bt cotton for managing bollworm. Consequently, foliar insecticide applications have been widely adopted to provide necessary additional control. Field experiments were conducted across the Mid-South and in Texas to devise economic thresholds for foliar insecticide applications targeting bollworm in cotton. Bt cotton technologies including TwinLink (TL; Cry1Ab+Cry2Ae), TwinLink Plus (TLP; Cry1Ab+Cry2Ae+Vip3Aa), Bollgard II (BG2; Cry1Ac+Cry2Ab), Bollgard 3 (BG3; Cry1Ac+Cry2Ab+Vip3Aa), WideStrike (WS; Cry1Ac+Cry1F), WideStrike 3 (WS3; Cry1Ac+Cry1F+Vip3Aa), and a non-Bt (NBT) variety were evaluated. Gain threshold, economic injury level, and economic thresholds were determined. A 6% fruiting form injury threshold was selected and compared with preventive treatments utilizing chlorantraniliprole. Additionally, the differences in yield from spraying bollworms was compared among Bt cotton technologies. The 6% fruiting form injury threshold resulted in a 25 and 75% reduction in insecticide applications relative to preventive sprays for WS and BG2, respectively. All Bt technologies tested in the current study exhibited a positive increase in yield from insecticide application. The frequency of yield increase from spraying WS was comparable to that of NBT. Significant yield increases due to insecticide application occurred less frequently in triple-gene Bt cotton. However, their frequencies were close to the dual-gene Bt cotton, except for WS. The results of our study suggest that 6% fruiting form injury is a viable threshold, and incorporating a vetted economic threshold into an Integrated Pest Management program targeting bollworm should improve the sustainability of cotton production.

REGULATING RISK: OVERSIGHT OF MICROBIAL PRODUCTS OF BIOTECHNOLOGY UNDER THE U.S. TOXIC SUBSTANCES CONTROL ACT

1999 ◽  
Vol 01 (03) ◽  
pp. 329-347 ◽  
Author(s):  
REBECCA A. EFROYMSON
Keyword(s):  
Environmental Protection ◽  
Environmental Protection Agency ◽  
Genetically Engineered ◽  
Institutional Constraints ◽  
Toxic Substances ◽  
Protection Agency ◽  
Microbial Products ◽  
Toxic Substances Control Act ◽  
Risk Oversight ◽  
The U.S

The Toxic Substances Control Act (TSCA) is the legislation used by the U.S. Environmental Protection Agency to regulate releases of genetically engineered microorganisms. The rule defining the scope of the notification requirements for releases of microbial products of biotechnology was published in April 1997. The Environmental Protection Agency (EPA) had some latitude regarding the extent to which various categories of microorganisms would be regulated, but the agency was constrained by requirements of TSCA and an interagency agreement about how to regulate products of biotechnology. This paper investigates the extent to which the scope of oversight is based on risk. A risk-based rule is defined as one where the reporting requirements are based on potential for exposure or expected adverse effects. The evolution of the rule is described, and risk-based components are discussed. In conclusion, the scope of oversight of microbial releases is determined to be based on risk to the extent that legislation and institutional constraints permit.

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