Browsing by Author "Nault, Brian A."
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- Epidemiology, Aphid Vectors, Impact and Management of Tobacco Etch Potyvirus in Hot Peppers in JamaicaMcDonald, Sharon Angella (Virginia Tech, 2001-02-22)Production of hot peppers, Capsicum spp., in Jamaica is constrained by the aphid-transmitted potyviruses, tobacco etch virus (TEV) and potato virus Y (PVY). The virus epidemiology was not understood and no effective virus management system existed for these viruses. This study sought to identify possible management strategies for aphid-transmitted viruses of hot peppers in Jamaica, using TEV and Capsicum chinense, var. 'Scotch Bonnet' and 'West Indian Red', as models. Field spread of TEV to pepper was mainly by secondary spread from primary infections. Secondary infections were spatially correlated to primary infections for up to 25 meters. Natural infections of TEV were associated with aphid flight activity. Over 30 species of aphids were collected on pepper farms in St. Catherine parish. These aphids included five known vectors of TEV, Aphis gossypii Glover, A. craccivora Koch, A. spiraecola Patch, Lipaphis erysimi Hille Ris Lambers and M. persicae (Sulzer), and 12 new records for Jamaica, Aphis amaranthi Holman, Brachycaudus helichrysi (Kaltenbach),Capitophorus hippophaes (Walker), Geopemphigus floccosus (Moreira), Hysteroneura setariae (Thomas), Lipaphis erysimi Hille Ris Lambers, Rhopalosiphum padi (Linnaeus), Schizaphis graminum (Rondani), Schizaphis rotundiventris (Signoret), Trichosiphonaphis poligoni (van der Goot), Uroleucon ambrosiae complex (Thomas) and Uroleucon pseudoambrosiae (Olive). A. amaranthi and U. ambrosiae were associated with TEV spread. Weeds on and near farms influenced the abundance and species of aphids captured. West Indian Red pepper showed tolerance to TEV. Scotch Bonnet pepper yield reduction was greater if plants were infected with TEV during the vegetative stage through flower initiation rather than after the start of fruit set. Stylet oil and reflective mulch used together delayed the incidence of TEV in pepper plots for over two months. TEV management programs should aim to delay the virus from infecting peppers during the first two months after transplanting. A risk analysis is proposed for management of TEV and other aphid-borne viruses.
- Extended Sentinel Monitoring of Helicoverpa zea Resistance to Cry and Vip3Aa Toxins in Bt Sweet Corn: Assessing Changes in Phenotypic and Allele Frequencies of ResistanceDively, Galen P.; Kuhar, Tom P.; Taylor, Sally V.; Doughty, Helene; Holmstrom, Kristian; Gilrein, Daniel O.; Nault, Brian A.; Ingerson-Mahar, Joseph; Huseth, Anders; Reisig, Dominic; Fleischer, Shelby; Owens, David; Tilmon, Kelley; Reay-Jones, Francis; Porter, Pat; Smith, Jocelyn; Saguez, Julien; Wells, Jason; Congdon, Caitlin; Byker, Holly; Jensen, Bryan; DiFonzo, Chris; Hutchison, William D.; Burkness, Eric; Wright, Robert; Crossley, Michael; Darby, Heather; Bilbo, Tom; Seiter, Nicholas; Krupke, Christian; Abel, Craig; Coates, Brad S.; McManus, Bradley; Fuller, Billy; Bradshaw, Jeffrey; Peterson, Julie A.; Buntin, David; Paula-Moraes, Silvana; Kesheimer, Katelyn; Crow, Whitney; Gore, Jeffrey; Huang, Fangneng; Ludwick, Dalton C.; Raudenbush, Amy; Jimenez, Sebastian; Carrière, Yves; Elkner, Timothy; Hamby, Kelly (MDPI, 2023-06-25)Transgenic corn and cotton that produce Cry and Vip3Aa toxins derived from Bacillus thuringiensis (Bt) are widely planted in the United States to control lepidopteran pests. The sustainability of these Bt crops is threatened because the corn earworm/bollworm, Helicoverpa zea (Boddie), is evolving a resistance to these toxins. Using Bt sweet corn as a sentinel plant to monitor the evolution of resistance, collaborators established 146 trials in twenty-five states and five Canadian provinces during 2020–2022. The study evaluated overall changes in the phenotypic frequency of resistance (the ratio of larval densities in Bt ears relative to densities in non-Bt ears) in H. zea populations and the range of resistance allele frequencies for Cry1Ab and Vip3Aa. The results revealed a widespread resistance to Cry1Ab, Cry2Ab2, and Cry1A.105 Cry toxins, with higher numbers of larvae surviving in Bt ears than in non-Bt ears at many trial locations. Depending on assumptions about the inheritance of resistance, allele frequencies for Cry1Ab ranged from 0.465 (dominant resistance) to 0.995 (recessive resistance). Although Vip3Aa provided high control efficacy against H. zea, the results show a notable increase in ear damage and a number of surviving older larvae, particularly at southern locations. Assuming recessive resistance, the estimated resistance allele frequencies for Vip3Aa ranged from 0.115 in the Gulf states to 0.032 at more northern locations. These findings indicate that better resistance management practices are urgently needed to sustain efficacy the of corn and cotton that produce Vip3Aa.
- Managing Colorado Potato Beetle Insecticide Resistance: New Tools and Strategies for the Next Decade of Pest Control in PotatoHuseth, Anders S.; Groves, Russell L.; Chapman, Scott A.; Alyokhin, Andrei; Kuhar, Thomas P.; MacRae, Ian V.; Szendrei, Zsofia; Nault, Brian A. (Entomological Society of America, 2014-12-01)Neonicotinoid insecticides have been the most common management tool for Colorado potato beetle, Leptinotarsa decemlineata (Say), infestations in cultivated potato for nearly 20 yr. The relative ease of applying neonicotinoids at planting coupled with inexpensive, generic neonicotinoid formulations has reduced the incentive for potato growers to transition from these products to other mode of action (MoA) groups for early-season L. decemlineata control. Continuous use of neonicotinoids has resulted in resistant L. decemlineata populations in some production areas of the eastern United States. Continued reliance on neonicotinoids will accelerate L. decemlineata resistance development and result in additional insecticide inputs to manage these populations. Resistance management recommendations for L. decemlineata have focused on rotation of insecticides within the growing season. Growers using at-plant neonicotinoids for early-season L. decemlineata control are encouraged to rotate MoAs for later generations to delay resistance development. Although this short-term insecticide rotation has likely prolonged the utility of neonicotinoid insecticides, reducing reliance on a single MoA soil application at planting will improve the longevity of newer, more reduced-risk alternatives. The objectives of this article are twofold: 1) to provide a review of the current status of L. decemlineata neonicotinoid resistance, and 2) to propose long-term resistance management strategies that arrange reduced-risk MoA groups into several, multiyear sequences that will maximize L. decemlineata control and reduce the probability for resistance development. This recommendation maintains practical and economical approaches for L. decemlineata control, but limits reliance on any single MoA group to minimize selection pressure for resistance development.