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Calvin W, Yang F, Kennedy H, Marçon PG, Kerns DL. Susceptibility of Field and Laboratory Bt-Susceptible and Resistant Strains of Helicoverpa zea (Boddie) to HearNPV. PLANTS (BASEL, SWITZERLAND) 2024; 13:529. [PMID: 38498539 PMCID: PMC10892202 DOI: 10.3390/plants13040529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 01/21/2024] [Accepted: 02/05/2024] [Indexed: 03/20/2024]
Abstract
During 2021 and 2022, eight field-collected and five laboratory Helicoverpa zea strains with varying susceptibility to different Bt proteins were evaluated for their responses against HearNPV using diet-overlay bioassays. The five laboratory strains included SS (susceptible to all Bt proteins), CRY-RR (resistant to Cry1 and Cry2), VIP-RR-70 (resistant to Vip3Aa), VIP-RR-15 (resistant to Vip3Aa), and TRE-RR (resistant to Cry1, Cry2, and Vip3Aa). Our findings showed that the susceptibility of TRE-RR, VIP-RR-70, and VIP-RR-15 strains to HearNPV was similar to that of the SS strain. However, the field and Cry-RR strains were more resistant to HearNPV compared to the SS strain. Because most feral H. zea strains in the southern U.S. have developed practical resistance to Cry Bt proteins but remain susceptible to Vip3Aa, the results suggest that the reduced susceptibility to HearNPV in H. zea may be associated with the resistance to Cry Bt proteins but not with the resistance to Vip3Aa. Correlation analysis confirmed that there was a significant positive relationship between Cry resistance and HearNPV resistance, but not between the Vip3Aa resistance and HearNPV resistance in H. zea. Our findings provide valuable insights into the relationship between susceptibility to HearNPV and resistance to Bt proteins in H. zea.
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Affiliation(s)
- Wilfrid Calvin
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843, USA
- Department of Entomology, University of Minnesota, Saint Paul, MN 55108, USA
| | - Fei Yang
- Department of Entomology, University of Minnesota, Saint Paul, MN 55108, USA
| | - Haley Kennedy
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843, USA
| | | | - David L Kerns
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843, USA
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Reisig D, Buntin GD, Greene JK, Paula-Moraes SV, Reay-Jones F, Roberts P, Smith R, Taylor SV. Magnitude and Extent of Helicoverpa zea Resistance Levels to Cry1Ac and Cry2Ab2 across the Southeastern USA. INSECTS 2023; 14:262. [PMID: 36975947 PMCID: PMC10058025 DOI: 10.3390/insects14030262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 02/27/2023] [Accepted: 03/02/2023] [Indexed: 06/18/2023]
Abstract
After resistance is first detected, continued resistance monitoring can inform decisions on how to effectively manage resistant populations. We monitored for resistance to Cry1Ac (2018 and 2019) and Cry2Ab2 (2019) from southeastern USA populations of Helicoverpa zea. We collected larvae from various plant hosts, sib-mated the adults, and tested neonates using diet-overlay bioassays and compared them to susceptible populations for resistance estimates. We also compared LC50 values with larval survival, weight and larval inhibition at the highest dose tested using regression, and found that LC50 values were negatively correlated with survival for both proteins. Finally, we compared resistance rations between Cry1Ac and Cry2Ab2 during 2019. Some populations were resistant to Cry1Ac, and most were resistant to CryAb2; Cry1Ac resistance ratios were lower than Cry2Ab2 during 2019. Survival was positively correlated with larval weight inhibition for Cry2Ab. This contrasts with other studies in both the mid-southern and southeastern USA, where resistance to Cry1Ac, Cry1A.105, and Cry2Ab2 increased over time and was found in a majority of populations. This indicates that cotton expressing Cry proteins in the southeastern USA was at variable risk for damage in this region.
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Affiliation(s)
- Dominic Reisig
- Department of Entomology, The Vernon James Center, North Carolina State University, Plymouth, NC 27962, USA
| | - G. David Buntin
- Department of Entomology, University of Georgia, Tifton, GA 31793, USA
| | - Jeremy K. Greene
- Department of Plant and Environmental Sciences, Clemson University, Blackville, SC 29817, USA
| | | | - Francis Reay-Jones
- Department of Plant and Environmental Sciences, Clemson University, Blackville, SC 29817, USA
| | - Phillip Roberts
- Department of Entomology, University of Georgia, Tifton, GA 31793, USA
| | - Ron Smith
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, USA
| | - Sally V. Taylor
- Department of Entomology, Virginia Polytechnic Institute and State University, Suffolk, VA 23437, USA
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Chester CC, Lien AM, Sundberg J, Diffendorfer JE, Gonzalez‐Duarte C, Mattsson BJ, Medellín RA, Semmens DJ, Thogmartin WE, Derbridge JJ, López‐Hoffman L. Using ecosystem services to identify inequitable outcomes in migratory species conservation. Conserv Lett 2022. [DOI: 10.1111/conl.12920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Charles C. Chester
- Environmental Studies Program Brandeis University Waltham Massachusetts USA
| | - Aaron M. Lien
- School of Natural Resources and the Environment University of Arizona Tucson Arizona USA
| | - Juanita Sundberg
- Department of Geography University of British Columbia Kelowna British Columbia USA
| | - Jay E. Diffendorfer
- U.S. Geological Survey, Geosciences and Environmental Change Science Center Denver Colorado USA
| | | | - Brady J. Mattsson
- Institute of Wildlife Biology and Game Management University of Natural Resources and Life Science Vienna Austria
| | - Rodrigo A. Medellín
- Institute of Ecology National Autonomous University of Mexico Mexico City Mexico
| | - Darius J. Semmens
- U.S. Geological Survey, Geosciences and Environmental Change Science Center Denver Colorado USA
| | - Wayne E. Thogmartin
- U.S. Geological Survey, Upper Midwest Environmental Science Center La Crosse Wisconsin USA
| | - Jonathan J. Derbridge
- School of Natural Resources and the Environment University of Arizona Tucson Arizona USA
| | - Laura López‐Hoffman
- School of Natural Resources and the Environment University of Arizona Tucson Arizona USA
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Rabelo MM, Santos IB, Paula-Moraes SV. Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) Fitness and Resistance Stability to Diamide and Pyrethroid Insecticides in the United States. INSECTS 2022; 13:insects13040365. [PMID: 35447807 PMCID: PMC9030708 DOI: 10.3390/insects13040365] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/30/2022] [Accepted: 04/06/2022] [Indexed: 11/21/2022]
Abstract
Simple Summary Spodoptera exigua is a polyphagous pest, commonly known as beet armyworm. This pest is distributed worldwide and causes yield reduction in a variety of crops. Chemical control using synthetic insecticides is the primary strategy to manage beet armyworm. In the United States, beet armyworm resistance to both chlorantraniliprole and bifenthrin insecticides was first reported in 2020. Here we examined beet armyworm fitness and stability of resistance to chlorantraniliprole and pyrethroid insecticides, since knowledge of the stability of resistance is a crucial aspect when recommending rotation of insecticides with different mode of action. Our results have indicated no decrease in bifenthrin resistance for at least a three-year period (i.e., 27 generations) when insecticide exposure was suspended. However, susceptibility to chlorantraniliprole dropped approximately 160-fold through this three-year period. Our results indicate that beet armyworm resistance to bifenthrin is stable, but unstable to chlorantraniliprole. Unstable resistance can be successfully managed at field level by switching off the selection pressure with replacement of the insecticide other than a pyrethroid. Abstract In the United States, beet armyworm resistance to both chlorantraniliprole and bifenthrin insecticides was first reported in 2020. Here we examined beet armyworm fitness and stability of resistance to chlorantraniliprole and pyrethroid insecticides since knowledge of the stability of resistance is a crucial aspect when recommending rotation of insecticides with different mode of action. Concentration-mortality bioassays were performed with field and laboratory susceptible populations. The F2, F13, and F27 generations of the field-derived population, maintained in the laboratory without insecticide, were exposed to commercial formulations of bifenthrin and chlorantraniliprole using the leaf-dip bioassay method (IRAC n. 007). Insects from F27 had the fitness components (survival, body weight, development time) documented and compared by LSM in each insecticide concentration tested. The resistance ratio to chlorantraniliprole reached 629, 80, 15-fold at F2, F13, and F27, respectively. These results contrast with an over 1000-fold resistance ratio to bifenthrin in all generations. The field-derived population had fitness reduced by chlorantraniliprole, but not by bifenthrin. In summary, the resistance of beet armyworm to bifenthrin was stable with no shift in fitness. In contrast, resistance to chlorantraniliprole was not stable through the generations kept in the laboratory without selection pressure, likely due to fitness cost.
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Black JL, Clark MK, Sword GA. Physiological and transcriptional immune responses of a non-model arthropod to infection with different entomopathogenic groups. PLoS One 2022; 17:e0263620. [PMID: 35134064 PMCID: PMC8824330 DOI: 10.1371/journal.pone.0263620] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 01/21/2022] [Indexed: 11/19/2022] Open
Abstract
Insect immune responses to multiple pathogen groups including viruses, bacteria, fungi, and entomopathogenic nematodes have traditionally been documented in model insects such as Drosophila melanogaster, or medically important insects such as Aedes aegypti. Despite their potential importance in understanding the efficacy of pathogens as biological control agents, these responses are infrequently studied in agriculturally important pests. Additionally, studies that investigate responses of a host species to different pathogen groups are uncommon, and typically focus on only a single time point during infection. As such, a robust understanding of immune system responses over the time of infection is often lacking in many pest species. This study was conducted to understand how 3rd instar larvae of the major insect pest Helicoverpa zea responded through the course of an infection by four different pathogenic groups: viruses, bacteria, fungi, and entomopathogenic nematodes; by sampling at three different times post-inoculation. Physiological immune responses were assessed at 4-, 24-, and 48-hours post-infection by measuring hemolymph phenoloxidase concentrations, hemolymph prophenoloxidase concentrations, hemocyte counts, and encapsulation ability. Transcriptional immune responses were measured at 24-, 48-, and 72-hours post-infection by quantifying the expression of PPO2, Argonaute-2, JNK, Dorsal, and Relish. This gene set covers the major known immune pathways: phenoloxidase cascade, siRNA, JNK pathway, Toll pathway, and IMD pathway. Our results indicate H. zea has an extreme immune response to Bacillus thuringiensis bacteria, a mild response to Helicoverpa armigera nucleopolyhedrovirus, and little-to-no detectable response to either the fungus Beauveria bassiana or Steinernema carpocapsae nematodes.
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Affiliation(s)
- Joseph L. Black
- Department of Entomology, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
| | - Mason K. Clark
- Department of Entomology, Texas A&M University, College Station, Texas, United States of America
| | - Gregory A. Sword
- Department of Entomology, Texas A&M University, College Station, Texas, United States of America
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Calvin W, Yang F, Brown SA, Catchot AL, Crow WD, Cook DR, Gore J, Kurtz R, Lorenz GM, Seiter NJ, Stewart SD, Towles T, Kerns DL. Development of Economic Thresholds Toward Bollworm (Lepidoptera: Noctuidae), Management in Bt Cotton, and Assessment of the Benefits From Treating Bt Cotton With Insecticide. JOURNAL OF ECONOMIC ENTOMOLOGY 2021; 114:2493-2504. [PMID: 34625803 DOI: 10.1093/jee/toab173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Indexed: 06/13/2023]
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.
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Affiliation(s)
- Wilfrid Calvin
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843, USA
| | - Fei Yang
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843, USA
| | - Sebe A Brown
- Dean Lee Research Station, Louisisana State University, 8105 Tom Bowman Drive, Alexandria, LA 71302, USA
| | - Angus L Catchot
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, P.O. Box 9775, Mississippi State, MS 39762, USA
| | - Whitney D Crow
- Delta REC, Mississippi State University, P.O. Box 197, Stoneville, MS 38776, USA
| | - Donald R Cook
- Delta REC, Mississippi State University, P.O. Box 197, Stoneville, MS 38776, USA
| | - Jeffrey Gore
- Delta REC, Mississippi State University, P.O. Box 197, Stoneville, MS 38776, USA
| | - Ryan Kurtz
- Cotton Incorporated, 6399 Weston Pkwy, Cary, NC 27513, USA
| | - Gustav M Lorenz
- Department of Entomology and Plant Pathology, University of Arkansas, 2001 Highway 70 E., Lonoke, AR 72086, USA
| | - Nicholas J Seiter
- Crop Sciences, 380 National Soybean Research Center, University of Illinois, 1101 W. Peabody Drive, Urbana, IL 61801, USA
| | - Scott D Stewart
- West Tennessee REC, University of Tennessee, 605 Airways Boulevard, Jackson, TN 38301, USA
| | - Tyler Towles
- Macon Ridge Research Station, Louisisana State University, 212A Macon Ridge Road, Winnsboro, LA 71295, USA
| | - David L Kerns
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843, USA
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7
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Babu A, Reisig DD, Pes MP, Ranger CM, Chamkasem N, Reding ME. Effects of chlorantraniliprole residual on Helicoverpa zea in Bt and non-Bt cotton. PEST MANAGEMENT SCIENCE 2021; 77:2367-2374. [PMID: 33415822 DOI: 10.1002/ps.6263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/30/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Helicoverpa zea is managed with foliar applications of chlorantraniliprole in cotton varieties that do not express the Vip3Aa19 toxin in the US Cotton Belt. Foliar insecticides and Bt could interact to influence larval susceptibility. Therefore, it has been suggested that chlorantraniliprole can be used as a tool for Bt resistance management. We designed field and laboratory studies to test the hypothesis that the interaction of Bt toxin and chlorantraniliprole application would result in lower H. zea larval survival when compared to the individual effect of Bt or chlorantraniliprole alone. We also tested for these interactions over time, since chlorantraniliprole residual has not been studied in cotton. RESULTS Results from two field experiments and two laboratory experiments were similar. We found no interactions with Bt and chlorantraniliprole using data not corrected for natural mortality in untreated plots, indicating that these factors did not interact to influence survival. Moreover, we found that Bt and chlorantraniliprole did not interact to influence larval weight and instar. Chlorantraniliprole had lethal and sublethal effects on H. zea larval growth parameters feeding on cotton leaves up to 22 days after application, the final time period that we tested. Finally, concentration of chlorantraniliprole in the leaf was associated with larval survival for the duration of this study, but not larval growth or instar. CONCLUSION Our findings complement the recommendation to use chlorantraniliprole for managing H. zea in cotton, given its long-residual effects. However, the utility of chlorantraniliprole as a Bt-resistance management tool for H. zea remains unclear. © 2021 Society of Chemical Industry.
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Affiliation(s)
- Arun Babu
- Department of Entomology and Plant Pathology, Vernon G. James Research and Extension Center, North Carolina State University, Plymouth, NC, USA
- Department of Entomology, College of Agricultural and Environmental Sciences, University of Georgia, 413 Biological Sciences, Athens, GA, 30602, USA
| | - Dominic D Reisig
- Department of Entomology and Plant Pathology, Vernon G. James Research and Extension Center, North Carolina State University, Plymouth, NC, USA
| | | | - Christopher M Ranger
- Application Technology Research Unit, USDA-Agricultural Research Service, Wooster, OH, USA
| | - Narong Chamkasem
- Southeast Regional Laboratory, U.S. Food and Drug Administration, Atlanta, GA, USA
| | - Michael E Reding
- Application Technology Research Unit, USDA-Agricultural Research Service, Wooster, OH, USA
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Del Pozo-Valdivia AI, Reisig DD, Braswell L, Greene JK, Roberts P, Taylor SV. Economic Injury Levels for Bt-resistant Helicoverpa zea (Lepidoptera: Noctuidae) in Cotton. JOURNAL OF ECONOMIC ENTOMOLOGY 2021; 114:747-756. [PMID: 33615386 DOI: 10.1093/jee/toab012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Indexed: 06/12/2023]
Abstract
Thresholds for Helicoverpa zea (Boddie) in cotton Gossypium hirsutum L. have been understudied since the widespread adoption of Bt cotton in the United States. Our study was possible due to the widespread presence of H. zea populations with Cry-toxin resistance. We initiated progressive spray timing experiments using three Bt cotton brands (Deltapine, Stoneville, and Phytogen) widely planted across the U.S. Cotton Belt expressing pyramided toxins in the Cry1A, Cry2, and Vip3Aa19 families. We timed foliar insecticide treatments based on week of bloom to manipulate H. zea populations in tandem with crop development during 2017 and 2018. We hypothesized that non-Bt cotton, cotton expressing Cry toxins alone, and cotton expressing Cry and Vip3Aa19 toxins would respond differently to H. zea feeding. We calculated economic injury levels to support the development of economic thresholds from significant responses. Pressure from H. zea was high during both years. Squares and bolls damaged by H. zea had the strongest negative yield associations, followed by larval number on squares. There were fewer yield associations with larval number on bolls and with number of H. zea eggs on the plant. Larval population levels were very low on varieties expressing Vip3Aa19. Yield response varied across experiments and varieties, suggesting that it is difficult to pinpoint precise economic injury levels. Nonetheless, our results generally suggest that current economic thresholds for H. zea in cotton are too high. Economic injury levels from comparisons between non-Bt varieties and those expressing only Cry toxins could inform future thresholds once H. zea evolves resistance to Vip3Aa19.
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Affiliation(s)
- Alejandro I Del Pozo-Valdivia
- Department of Entomology, Hampton Roads Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Virginia Beach, VA, USA
| | - Dominic D Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, Vernon G. James Research and Extension Center, Plymouth, NC, USA
| | - Lewis Braswell
- Product Biology Division, Syngenta Crop Protection Inc., Greensboro, NC, USA
| | - Jeremy K Greene
- Department of Plant and Environmental Sciences, Edisto Research and Education Center, Clemson University, Blackville, SC, USA
| | - Phillip Roberts
- Department of Entomology, University of Georgia, Tifton Campus, Tifton, GA, USA
| | - Sally V Taylor
- Department of Entomology, Tidewater Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Suffolk, VA, USA
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Rabelo MM, Paula-Moraes SV, Pereira EJG, Siegfried BD. Contrasting susceptibility of lepidopteran pests to diamide and pyrethroid insecticides in a region of overwintering and migratory intersection. PEST MANAGEMENT SCIENCE 2020; 76:4240-4247. [PMID: 32614113 DOI: 10.1002/ps.5984] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 04/25/2020] [Accepted: 07/02/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Pesticide resistance is a growing issue worldwide, and susceptibility of pest populations should be monitored in migratory intersection regions for successful resistance management. We determined the susceptibility of eight noctuid species from the Florida Panhandle to bifenthrin (pyrethroid) and chlorantraniliprole (diamide). Larvae from field and laboratory populations were exposed to commercial insecticide formulations using the leaf-dip method in concentration-mortality bioassays. RESULTS The field populations of Helicoverpa zea (Boddie), Spodoptera frugiperda (Smith), S. eridania (Stoll), S. exigua (Hubner) and Chloridea virescens (Fabricius) had reduced susceptibility to bifenthrin compared with the laboratory populations. Resistance ratios to bifenthrin were as high as 10 071-fold in S. exigua and 436-fold in S. frugiperda, while there was no reduced susceptibility in Agrotis ipsilon (Hufnagel). The susceptibility to chlorantraniliprole was similar between the field and laboratory populations studied, except for S. exigua that exhibited 630-fold resistance to the diamide. The probit regression equations indicated that the larval mortality of S. exigua and S. frugiperda populations was <80% with bifenthrin at the concentration equivalent to the label rate. Likewise, the estimated mortality of S. exigua larvae with chlorantraniliprole at the label rate concentration was <80%. CONCLUSIONS The lepidopteran pest populations tested were variable in susceptibility to bifenthrin by contrast to more consistent susceptibility to chlorantraniliprole. These results help in the choice of effective insecticides for integrated pest management and resistance management in cropping systems colonized by migratory lepidopteran pests from the U.S. Gulf Coast region. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Marcelo M Rabelo
- Department of Entomology, Universidade Federal de Viçosa, Viçosa, Brazil
- Department of Entomology and Nematology, West Florida Research and Education Center, University of Florida, Jay, FL, USA
| | - Silvana V Paula-Moraes
- Department of Entomology and Nematology, West Florida Research and Education Center, University of Florida, Jay, FL, USA
| | - Eliseu José G Pereira
- Department of Entomology, Universidade Federal de Viçosa, Viçosa, Brazil
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, Brazil
| | - Blair D Siegfried
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
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Demographic Performance of Helicoverpa zea Populations on Dual and Triple-Gene Bt Cotton. Toxins (Basel) 2020; 12:toxins12090551. [PMID: 32872277 PMCID: PMC7551585 DOI: 10.3390/toxins12090551] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 08/10/2020] [Accepted: 08/26/2020] [Indexed: 01/02/2023] Open
Abstract
Insecticidal toxins from Bacillus thuringiensis (Bt) are valuable tools for pest management worldwide, contributing to the management of human disease insect vectors and phytophagous insect pests of agriculture and forestry. Here, we report the effects of dual and triple Bt toxins expressed in transgenic cotton cultivars on the fitness and demographic performance of Helicoverpa zea (Boddie)—a noctuid pest, known as cotton bollworm and corn earworm. Life-history traits were determined for individuals of three field populations from a region where H. zea overwintering is likely. Triple-gene Bt cotton cultivars that express Cry and Vip3Aa toxins killed 100% of the larvae in all populations tested. In contrast, dual-gene Bt cotton that express Cry1Ac+Cry1F and Cry1Ac+Cry2Ab allowed population growth with the intrinsic rate of population growth (rm) 38% lower than on non-Bt cotton. The insects feeding on Bt cotton plants that express Cry1Ac+Cry2Ab, Cry1Ac+Cry1F, or Cry1Ab+Cry2Ae exhibited reduced larval weight, survival rate, and increased development time. Additionally, fitness parameters varied significantly among the insect populations, even on non-Bt cotton plants, likely because of their different genetic background and/or previous Bt toxin exposure. This is the first report of the comparative fitness of H. zea field populations on dual-gene Bt cotton after the recent reports of field resistance to certain Bt toxins. These results document the population growth rates of H. zea from an agricultural landscape with 100% Bt cotton cultivars. Our results will contribute to the development and validation of resistance management recommendations.
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