Browsing by Author "Wimer, Adam Francis"

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    Performance of Insecticides on Brown Marmorated Sting Bug on Vegetables
    Kuhar, Thomas P.; Doughty, Hélène; Kamminga, Katherine; Philips, Chris; Aigner, John D.; Wallingford, Anna K.; Wimer, Adam Francis; Lilliston, Logan; Aigner, Benjamin L.; Nottingham, Louis B.; Lohr, Ashley; Fread, Elizabeth; Jenrette, James (Virginia Cooperative Extension, 2011)
    Lists the rankings of insecticides used in a series of experiments in terms of percentage of mortality for Brown Marmorated Stink Bug nymphs and adults.
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    Resistance evaluation and management of Colorado potato beetle, Leptinotarsa decemlineata (Say), using novel chemistries
    Wimer, Adam Francis (Virginia Tech, 2013-06-14)
    Leptinotarsa decemlineata (Say) is the most important defoliating pest of potato Solanum tuberosum L., in North America and Europe.  Management of this pest relies heavily on chemical control and insecticide resistance is a persistent problem.  This phenomenon has increased the need for developing novel insecticides, resistance evaluation, and the development of alternative control strategies regarding this insect pest.  From 2010 to 2013, field and lab experiments were conducted to evaluate the efficacy of a novel insecticide tolfenpyrad on L. decemlineata.  In leaf-dip assays, tolfenpyrad was highly toxic to L. decemlineata with LC50 values of 0.013 and 0.164 g ai/L for larvae and adults, respectively.  Tolfenpyrad was also toxic to eggs with 0% hatching after being dipped in a field rate concentration.  In field efficacy trials, potato plots treated with tolfenpyrad at rates as low as 153 g ai/ha effectively controlled L. decemlineata. In 2012, populations of L. decemlineata were collected from the Eastern Shore of VA and subjected to toxicity assays to determine current susceptibility to permethrin and oxamyl.  The toxicity assays indicated an increase in toxicity to permethrin in L. decemlineata larvae (LC50 = 3.931 g ai/L) and an increase in toxicity to oxamyl in adult beetles (LC50 = 9.695 g ai/L) compared with LC50 values previously reported in 1990.  In 2012, populations of L. decemlineata from Cheriton, VA, New Church, VA, Painter, VA, and Plymouth, NC were also evaluated for enzyme activity after exposure to sub-lethal concentrations of permethrin, oxamyl, and tolfenpyrad.  Adult beetles were subjected to enzyme assays to measure the activity of cytochrome P450 mono-oxygenase (P450), glutathione-S-transferase (GST), general esterases, and protein content.  Results from the enzyme assays indicated significantly greater esterase activity in beetles from Painter, VA exposed to permethrin [±-naphthol (F= 11.66, df= 4, 20, P<0.0001) and "-naphthol (F= 11.86, df= 4, 20, P<0.0001)], oxamyl [±- naphthol (F= 10.64, df= 4, 20, P<0.0001) and "-naphthol (F= 6.94, df= 4, 20, P=0.0011)], tolfenpyrad [±- naphthol (F= 407.62, df= 1, 8, P<0.0001) and "- naphthol (F= 28.15, df= 1, 8, P= 0.0007)], and the untreated control [±- naphthol (F= 28.14, df= 3, 16, P<0.0001) and "- naphthol (F= 28.86; df= 3, 16, P<0.0001)] compared to most of the other populations tested.  GST activity was significantly greater in tolfenpyrad exposed beetles compared to the non-treated beetles from Painter VA (F= 17.66, df= 5, 24, P< 0.0001). Through laboratory assays and field experiments in potato, the efficacy of a new bio-pesticide derived from the bacterium Chromobacterium subtsugae was evaluated for the control of L. decemlineata.  Results from the laboratory assays showed L. decemlineata feeding was inhibited by the bio-pesticide derived from C. subtsugae.  However, field efficacy trials in 2010, 2011, and 2012, indicated no control of L. decemlineata. Methyl salicylate is an organic compound produced by potato and other plants in response to insect herbivory.  Abundance of predatory arthropods and L. decemlineata life stages were measured in plots treated with and without 5 g slow-release packets of methyl salicylate (95% methyl salicylate (Predalure")).  Methyl salicylate treatment had no impact on predator recruitment or cumulative mortality of L. decemlineata in potatoes. This research has provided us with a new tool for L. decemlineata management, as well as more information about resistance trends and alternative control strategies from which we can build on to reduce resistance development in L. decemlineata and ultimately formulate a stronger integrated pest management strategy for this insect pest.
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    The Spatial and Temporal Distribution and Management of Tomato Bacterial Wilt on Virginia's Eastern Shore
    Wimer, Adam Francis (Virginia Tech, 2009-12-09)
    In 2007 and 2008 more than 100 million dollars of fresh market tomatoes were grown in Virginia, with the majority of production occurring on the Eastern Shore of Virginia (ESV), according to the National Agricultural Statistics Service. Bacterial wilt of tomato, caused by Ralstonia solanacearum (Smith) and Yabucchi et al., is the most devastating disease of tomato on the ESV. Four 'observational trials' were conducted on the ESV over three growing seasons to determine the temporal and spatial distribution of this disease in commercial tomato fields. Plants were assessed at approximately one-week intervals throughout the growing seasons and the incidence of bacterial wilt for each individual plant was recorded. A steady increase in both disease incidence and clustered distribution of the disease within rows was observed as the growing season progressed. Positive correlations between disease incidence and percentage of rows exhibiting a significant clustered distribution occurred in all trials, which indicated an increase in clustered distribution as disease incidence increased. Research trials were conducted over three years, beginning in the summer of 2007, to investigate the effects of tomato bacterial wilt resistant cultivars on the ESV. In 2008 and 2009, the selective, systemic compound which induces host plant resistance, acibenzolar-S-methyl (ASM) was incorporated into resistant cultivar trials. Results from the 2007 trial revealed significant resistance in some of the breeding lines, CRA 66 and PI 126408. The 2008 and 2009 trials revealed that ASM was not effective at reducing levels of bacterial wilt. Grafted transplants in the spring trials of 2008 and 2009 had varied results in resistance and yield. Results revealed the tomato cultivar BHN 669 was an excellent resistant cultivar with promising yield potential and fruit quality.