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 Co-occurrence of kdr Mutations V1016I and F1534C and Its Association With Phenotypic Resistance to Pyrethroids in Aedes aegypti (Diptera: Culicidae) Populations From Costa Rica

2019 ◽  
Vol 57 (3) ◽  
pp. 830-836
Author(s):  
Aryana Zardkoohi ◽  
David Castañeda ◽  
Juan C Lol ◽  
Carmen Castillo ◽  
Francisco Lopez ◽  
...  
Keyword(s):  
Costa Rica ◽  
Aedes Aegypti ◽  
Insecticide Resistance ◽  
Vector Control ◽  
Strong Association ◽  
Resistance Management ◽  
Management Plan ◽  
Costa Rican ◽  
Mosquito Vector ◽  
Phenotypic Resistance

Abstract Aedes aegypti (Linnaeus, 1762) is considered the most important mosquito vector species for several arboviruses (e.g., dengue, chikungunya, Zika) in Costa Rica. The primary strategy for the control and prevention of Aedes-borne diseases relies on insecticide-based vector control. However, the emergence of insecticide resistance in the mosquito populations presents a significant threat to these prevention actions. The characterization of the mechanisms driving the insecticide resistance in Ae. aegypti is vital for decision making in vector control programs. Therefore, we analyzed the voltage-gated sodium channel (VGSC) gene for the presence of the V1016I and F1534C kdr mutations in Ae. aegypti populations from Puntarenas and Limon provinces, Costa Rica. The CDC bottle bioassays showed that both Costa Rican Ae. aegypti populations were resistant to permethrin and deltamethrin. In the case of kdr genotyping, results revealed the co-occurrence of V1016I and F1534C mutations in permethrin and deltamethrin-resistant populations, as well as the fixation of the 1534C allele. A strong association between these mutations and permethrin and deltamethrin resistance was found in Puntarenas. Limon did not show this association; however, our results indicate that the Limon population analyzed is not under the same selective pressure as Puntarenas for the VGSC gene. Therefore, our findings make an urgent call to expand the knowledge about the insecticide resistance status and mechanisms in the Costa Rican populations of Ae. aegypti, which must be a priority to develop an effective resistance management plan.

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.

scholarly journals Genetically modified soybean expressing insecticidal protein (Cry1Ac): Management risk and perspectives

FACETS ◽  
2017 ◽  
Vol 2 (1) ◽  
pp. 496-512 ◽  
Author(s):  
Silvia Martins-Salles ◽  
Vilmar Machado ◽  
Laura Massochin-Pinto ◽  
Lidia M. Fiuza
Keyword(s):  
Pest Control ◽  
Crop Production ◽  
Insect Pest ◽  
Rapid Evolution ◽  
Resistance Management ◽  
Agricultural Practices ◽  
Genetically Modified Soybean ◽  
Bt Crops ◽  
Lepidopteran Pests ◽  
Bt Toxins

A Bt soybean has been recently developed, thus, efficiently regulating the populations of major lepidopteran pests. However, in other cases, these benefits have been reduced or lost because of the rapid evolution of pest resistance to the Bt toxins in transgenic crops. When pest populations are exposed to Bt crops and to refuges (non- Bt plants), the evolution of resistance is governed by the fitness of resistant individuals relative to susceptible individuals for both the presence and absence of Bt toxins. One major ecological concern regarding the biosafety of Bt crops on the environment is their potential effects on non-target organisms, especially predators and parasitoids that play an important role in pest control. This information is important for supporting insect resistance management (IRM) programs and for improving agricultural practices in a crop production system with Bt plants. Before the use of Bt plants for insect pest control in Brazil is adopted, IRM programs should be established to ensure the sustainability of this technology for integrated pest management (IPM). This review presents data on Bt soybean and lepidopteran pests as well as on the importance of natural enemies as a form of biological control, and applications for IPM and IRM.

scholarly journals Insecticidal Activity and Synergistic Combinations of Ten Different Bt Toxins against Mythimna separata (Walker)

Toxins ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 454 ◽  
Author(s):  
Jing Yang ◽  
Yudong Quan ◽  
Prabu Sivaprasath ◽  
Muhammad Shabbir ◽  
Zhenying Wang ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Resistance Management ◽  
Agricultural Crops ◽  
New Combinations ◽  
Mythimna Separata ◽  
Recombinant Bacteria ◽  
Bt Crops ◽  
Bt Toxins ◽  
Neonate Larvae ◽  
Synergistic Combinations

The oriental armyworm (OAW), Mythimna separata (Walker), is a destructive pest of agricultural crops in Asia and Australia. Commercialized Bt crops have performed very well against their target pests; however, very few studies have been done on the susceptibility of OAW to Bt toxins in either sprays or expressed in Bt crops. In this work, we evaluated the toxicities of Cry1Ab, Cry1Ac, Cry1Ah, Cry1Fa, Cry2Aa, Cry2Ab, Cry1Ie, Vip3Aa19, Vip3Aa16, and Vip3Ca against OAW neonate larvae, as well as the interaction between Cry and Vip toxins. The results from bioassays revealed that LC50 (lethal concentration for 50% mortality) values ranged from 1.6 to 78.6 μg/g (toxin/diet) for those toxins. Among them, Vip3 proteins, along with Cry1A proteins and Cry2Aa, were the ones with the highest potency, with LC50 values ranging from 1.6 to 7.4 μg/g. Synergism between Cry and Vip toxins was observed, being high in the combination of Vip3Aa16 with Cry1 toxins, with synergetic factors ranging from 2.2 to 9.2. The Vip3Ca toxin did not show any synergistic effect with any of the toxins tested. These results can help in designing new combinations of pyramiding genes in Bt crops, as well as in recombinant bacteria, for the control of OAW as well as for resistance management programs.

scholarly journals Plot Refugi untuk Pengelolaan Resistensi Hama terhadap Tanaman Transgenik Bt

2011 ◽  
Vol 7 (2) ◽  
pp. 128
Author(s):  
Bahagiawati Bahagiawati
Keyword(s):  
Insect Resistance ◽  
Resistance Management ◽  
The Philippines ◽  
Bt Cotton ◽  
Isogenic Line ◽  
Field Mode ◽  
Bt Crops ◽  
Bt Toxin ◽  
Refuge Strategy ◽  
Bt Crop

<p>Refugea Plot as Insect Resistance Management in<br />Transgenic Bt Crops. Bahagiawati. The objective of this<br />review is to share information on several cases of target<br />insects became resistance to transgenic-Bt crops in the field<br />and the refuge strategy used to manage this problem. Bt<br />corn and Bt cotton have been planted widely for several<br />years globally. One of the risks of planting transgenic Bt crop<br />is the ability of the target insects adapted to the Bt protein<br />and caused the resistance breakdown the transgenic Bt<br />plants. This phenomenon was hypothesized in early 1990s<br />based on the cases of several insects resistance to microbial<br />Bt sprayed in laboratories and in the field. The mode of<br />action of the pest resistance to Bt-toxin have been studied in<br />several laboratories. In USA, to avoid the target insect<br />resistance to transgenic Bt crops, a program called Insect<br />Resistance Management (IRM) has been applied since 2001<br />for farmers growing Bt crops. Lately, there have been some<br />reports of target insects became resistance to cry1F, cry1Ab,<br />and cry1Ac in transgenic Bt crops. A report informed about<br />the resistance of target insect in Puerto Rico was published<br />in 2006, and so in South Africa in 2006/2007, and the last one<br />in India in 2009. To avoid target’s insect become resistance<br />to Bt crops, a program called structural IRM and unstructural<br />IRM were introduced and applied in several<br />countries. One of the components of IRM is planting refuge<br />plot, a plot that planting with isogenic line of Bt crops in/near<br />by the area of Bt crops. This review will discuss about the<br />cases of target insect became resistance to Bt crops in the<br />field, mode of action of insect resistance to Bt, the model of<br />IRM program in USA and the Philippines and finally the<br />recommendation for Indonesia to prepare its IRM program<br />for implementing Bt crops.</p>

Long-Term Empirical and Observational Evidence of Practical Helicoverpa zea Resistance to Cotton With Pyramided Bt Toxins

2018 ◽  
Vol 111 (4) ◽  
pp. 1824-1833 ◽  
Author(s):  
Dominic D Reisig ◽  
Anders S Huseth ◽  
Jack S Bacheler ◽  
Mohammad-Amir Aghaee ◽  
Lewis Braswell ◽  
...  
Keyword(s):  
Helicoverpa Zea ◽  
Observational Evidence ◽  
Bt Toxins

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 Differences between two populations of bollworm, Helicoverpa zea (Lepidoptera: Noctuidae), with variable measurements of laboratory susceptibilities to Bt toxins exposed to non-Bt and Bt cottons in large field cages

PLoS ONE ◽  
2019 ◽  
Vol 14 (3) ◽  
pp. e0212567 ◽  
Author(s):  
Nathan S. Little ◽  
Blake H. Elkins ◽  
R. Michelle Mullen ◽  
Omaththage P. Perera ◽  
Katherine A. Parys ◽  
...  
Keyword(s):  
Helicoverpa Zea ◽  
Large Field ◽  
Bt Toxins ◽  
Lepidoptera Noctuidae ◽  
Two Populations
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