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Browsing by Author "Roberts, Phillip"

Now showing 1 - 4 of 4
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    Magnitude and Extent of Helicoverpa zea Resistance Levels to Cry1Ac and Cry2Ab2 across the Southeastern USA
    Reisig, Dominic; Buntin, G. David; Greene, Jeremy K.; Paula-Moraes, Silvana V.; Reay-Jones, Francis; Roberts, Phillip; Smith, Ron; Taylor, Sally V. (MDPI, 2023-03-07)
    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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    Managing Stink Bugs in Cotton: Research in the Southeast Region
    Herbert, D. Ames Jr.; Blinka, Eric; Bacheler, Jack S.; Van Duyn, J. W.; Greene, Jeremy K.; Roberts, Phillip; Smith, Ron H. (Virginia Cooperative Extension, 2018-11-13)
    Describes the damage to cotton and economic impact of three species of stink bugs in the southeastern United States. Provides information on assessing population levels of stink bugs in cotton fields.
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    Managing Stink Bugs in Cotton: Research in the Southeast Region
    Herbert, D. Ames Jr.; Blinka, Eric; Bacheler, Jack S.; Van Duyn, J. W.; Greene, Jeremy K.; Roberts, Phillip; Smith, Ron H. (Virginia Cooperative Extension, 2009)
    Describes the damage to cotton and economic impact of three species of stink bugs in the southeastern United States. Provides information on assessing population levels of stink bugs in cotton fields.
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    The Spatiotemporal Distribution, Abundance, and Seasonal Dynamics of Cotton-Infesting Aphids in the Southern U.S.
    Mahas, John W.; Mahas, Jessica B.; Ray, Charles; Kesheimer, Adam; Steury, Todd D.; Conzemius, Sophia R.; Crow, Whitney; Gore, Jeffrey; Greene, Jeremy K.; Kennedy, George G.; Kerns, David; Malone, Sean; Paula-Moraes, Silvana; Roberts, Phillip; Stewart, Scott D.; Taylor, Sally; Toews, Michael; Jacobson, Alana L. (MDPI, 2023-07-15)
    Cotton leafroll dwarf virus (CLRDV) is an emerging aphid-borne pathogen infecting cotton, Gossypium hirsutum L., in the southern United States (U.S.). The cotton aphid, Aphis gossypii Glover, infests cotton annually and is the only known vector to transmit CLRDV to cotton. Seven other species have been reported to feed on, but not often infest, cotton: Protaphis middletonii Thomas, Aphis craccivora Koch, Aphis fabae Scopoli, Macrosiphum euphorbiae Thomas, Myzus persicae Sulzer, Rhopalosiphum rufiabdominale Sasaki, and Smynthurodes betae Westwood. These seven have not been studied in cotton, but due to their potential epidemiological importance, an understanding of the intra- and inter-annual variations of these species is needed. In 2020 and 2021, aphids were monitored from North Carolina to Texas using pan traps around cotton fields. All of the species known to infest cotton, excluding A. fabae, were detected in this study. Protaphis middletonii and A. gossypii were the most abundant species identified. The five other species of aphids captured were consistently low throughout the study and, with the exception of R. rufiabdominale, were not detected at all locations. The abundance, distribution, and seasonal dynamics of cotton-infesting aphids across the southern U.S. are discussed.