Browsing by Author "George G. Kennedy, Committee Co-Chair"

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Mating disruption for control of the Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera:Tortricidae), in North Carolina apple orchards.
(2003-07-31) Kovanci, Orkun B; Coby Schal, Committee Member; George G. Kennedy, Committee Co-Chair; Turner B. Sutton, Committee Member; James F. Walgenbach, Committee Co-Chair
Oriental fruit moth, Grapholita molesta (Busck), has been a primary pest of peaches for many years throughout the world, and recently it has also emerged as a key pest of apples in the eastern United States. The implementation of the Food Quality Protection Act has eliminated the use of many organophosphate insecticides and encouraged the search for alternatives to organophosphates for control of Oriental fruit moth. Large and small plot studies were conducted to evaluate mating disruption as an alternative control tactic against Oriental fruit moth in North Carolina apple orchards during 2000-2002. The efficacy of Isomate-M 100 pheromone dispensers and microencapsulated sprayable pheromone was compared to insecticide-treated and non-managed orchards. Pheromone trap catches were significantly reduced in mating disruption blocks compared with conventional and non-managed orchards. Pheromone traps placed in the upper canopy captured significantly more moths than traps placed in the lower canopy across all treatments. Male OFM responded optimally to traps baited with 100 μg lures compared with 30 and 300 μg lures regardless of treatment. The loss of OFM pheromone from red rubber septa over a four-wk period exhibited a first-order release rate for septa loaded with 100 and 300 μg pheromone, but a more constant release rate from septa loaded with 30 μg pheromone. Based on pheromone trap captures, there was little difference among rates of sprayable pheromone ranging from 12.4 to 49.1 g (ai)/ha, but efficacy declined at 2.4 g (ai)/ha applied at monthly intervals. The 6.2 g (ai)/ha rate applied at 2-wk intervals was significantly less effective than monthly applications of 12.4 and 24.7 g (ai)/ha. Significantly fewer moths were caught in pheromone traps deployed in blocks treated in late May with Isomate-M 100, Isomate-M Rosso and Isomate-M 100 plus 3M sprayable pheromone compared with traps in conventional insecticide treatments, and Isomate-M 100 applied in late June. Overall, fruit damage by OFM larvae was quite low in mating disruption blocks.
Oriental fruit moth phenology in North Carolina apples and ecdysone agonist activity on oriental fruit moth and codling moth.
(2003-06-13) Borchert, Daniel Michael; James F. Walgenbach, Committee Co-Chair; George G. Kennedy, Committee Co-Chair; Ronald Stinner, Committee Member; Turner B. Sutton, Committee Member
Oriental fruit moth, Grapholita molesta (Busck) and codling moth, Cydia pomonella (L.), are internal fruit pests of apple. Codling moth is recognized as a pest of apple, but until the last several years, oriental fruit moth was considered primarily a pest of peaches. Elimination or reduction of organophosphate insecticides and their replacement with reduced-risk insecticides has created the need to evaluate the activity and efficacy of these newly introduced insecticides. The purpose of this research was to evaluate the activity of the ecdysone agonists tebufenozide and methoxyfenozide for codling moth and oriental fruit moth and to develop management strategies for early season control of the two pests. Methoxyfenozide had greater activity than tebufenozide on codling moth and oriental fruit moth eggs and was active for at least 28 d. Residue breakdown of the two ecdysone agonists was similar, with 60 and 80% decline at 14 and 28 d after application, respectively. Effects of sublethal exposure to methoxyfenozide on the population dynamics of oriental fruit moth was studied in single tree cages and laboratory studies. Population differences were observed between treated and untreated field cages, but could not be directly attributed to sublethal effects of methoxyfenozide; no sublethal effects were observed in laboratory studies. The phenology of oriental fruit moth was studied using egg sampling and pheromone traps to increase the knowledge of the pest in apple. Oriental fruit moth eggs were found on cluster leaves early and on fruit late in the season, predominantly on the top leaf surface and calyx end of the fruit. A degree-day model for oriental fruit moth oviposition was developed and the start of second-generation oviposition was predicted to occur at 507 DD (7.2 C base temp) after peak trap catch. Spray timing of methoxyfenozide was varied for control of codling moth and oriental fruit moth; two applications applied at 21-d spray intervals provided high levels of control for both pests.
Phenology of the Twospotted Spider Mite Tetranychus urticae (Acari: Tetranychidae) in North Carolina Tomato Systems
(2007-04-25) Meck, Elijah; James F. Walgenbach, Committee Co-Chair; George G. Kennedy, Committee Co-Chair; David W. Monks, Committee Member
The twospotted spider mite, Tetranychus urticae Koch, is a cosmopolitan and highly polyphagous pest of many fruits, vegetables, ornamentals, and field crops. While twospotted spider mite is a well-documented pest of corn and peanuts in eastern North Carolina, only recently has it been recognized as a consistent and serious pest of vegetables in the piedmont and mountains of North Carolina. Mites infest a number of vegetables in North Carolina including tomato, pepper, eggplant, and sweet corn, but tomato is by far the most seriously affected crop. The objectives of this study were to 1) determine the effect of vegetation on the dispersal of twospotted spider mites from tomatoes to overwintering hosts, and 2) to investigate the potential importance of various factors, including location, planting date, field history, surrounding area, pesticide use, and mite populations in surrounding vegetation, that may affect mite infestations in tomato fields in different regions of North Carolina. Two vegetation management techniques (herbicide and cultivation) plus an untreated control plot were established around senescing tomato plants. Twospotted spider mite dispersal was monitored by planting chickweed trap plants at 2, 6, and 12 m from the tomatoes. Sampling took place in the fall of 2004 & 2005 and the spring of 2005 & 2006. Only a small number of mites were collected in the 2004-2005 sampling period, making it difficult to draw conclusions. The 2005-2006 sampling period showed that herbicide-treated soil facilitated mite dispersal in the fall, while there were no differences in mite populations among treatments in the spring, suggesting a high rate of overwintering mortality. Tomato fields in the mountains and piedmont region were sampled in a grid pattern on a bimonthly basis to determine the importance of year, location, planting date, previous crop, adjacent crop, insecticide use, acaricide use, and mite populations in surrounding vegetation on mite intensities in those fields. Based on samples from 80 tomato fields, previous crop, acaricide use, insecticide use, and mite intensity in the weeds were important factors that were associated with seasonal mite intensity in tomato fields. Acaricide use and mite intensity in the weeds were important factors associated with the maximum mite intensity in tomatoes. Year, location, planting date, and acaricide use were all important factors associated with the time it took for tomato fields to reach their maximum density. Upon further analysis, it was found that none of the dependent variables (year, location, previous crop, adjacent crop, planting date, acaricide use, insecticide use) were associated with seasonal mite intensity in weeds or mite intensity in weeds on the last two sample dates. However, previous crop and insecticide use were significant factors associated with mite intensity in weeds on the first two sample dates. Furthermore, seasonal mite intensity in weeds was significantly correlated with seasonal and maximum mite intensity in tomato fields. While previous crop, current season insecticide use, and mite intensity in weeds were factors associated with mite intensities in the field, a high overwintering mortality appeared to negate the effects of these factors; consequently it was not possible to predict in advance fields that were most susceptible to high mite infestations. Acaricides will likely remain a key management strategy in the near future, and the development of sampling plans and economic thresholds will be necessary to use these materials in a judicious manner.
Population genetic analysis of Tomato spotted wilt virus (TSWV) on peanut in North Carolina and Virginia.
(2009-07-07) Kaye, Amanda Claire; George G. Kennedy, Committee Co-Chair; James W. Moyer, Committee Member; Marc A. Cubeta, Committee Co-Chair; Barbara B. Shew, Committee Member
Exploring the genetic diversity and evolutionary history of plant viruses is critical to understanding their ecology and epidemiology. Tomato spotted wilt virus (TSWV) is an ambisense RNA virus that infects over 1000 species of plants and has been shown to reassort its genome. To further investigate this virus, maximum-likelihood and population genetics-based methods were used to investigate the population structure, genetic diversity, and sources of genetic variation in field isolates of TSWV from peanut in North Carolina and Virginia. Selected regions of the nucleocapsid, movement, and RNA-dependent RNA polymerase genes were amplified and sequenced to identify haplotypes and infer genetic relationships between isolates of TSWV with heuristic methods. The haplotype structure of each locus consisted of one or two predominant haplotypes and more than 100 haplotypes represented by a single isolate. No specific haplotypes or clades were associated with geographic area, peanut cultivar or year. The population was panmictic at the regional level and high levels of genetic diversity were observed among isolates. There was evidence for negative selection acting upon each locus and maximum-likelihood analyses indicated that exponential growth was occurring in the population. The results of compatibility analyses and the persistence of specific gene sequences in isolates collected over three field seasons suggest that recombination was occurring in the population. Phylogenetic analysis supports that each locus has an independent evolutionary history. Also, high diversity in viruses has been attributed to the occurrence of recombination and mutation To investigate recombination in TSWV, matrix compatibility and ancestral recombination methods were used to detect, quantify, and reconstruct the history of recombination in three genes of TSWV in isolates collected from three cultivars of peanut (Gregory, NC12C, and Perry) sampled in multiple years. Site commonalities among the isolates collected from different cultivars were found in each gene where the majority of the recombination appeared to be occurring. These corresponded to sequence near the 3Ã¢â‚¬Â² terminus in the N and RdRP genes and to sequence near the 5Ã¢â‚¬Â² terminus in the NSm gene. Between isolates collected from different peanut cultivars, the Gregory isolates proportionally had the most recombination occurring in the N gene and the RdRP genes, while the Perry isolates had the most recombination occurring in the NSm. Recombination rates per site estimated for the N, NSm, and RdRP genes in the NC12C isolates were 0.00934, 0.01559, and 0.00495, respectively.