Browsing by Author "Onufrieva, Ksenia S."
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- Bounds on Absolute Gypsy Moth (Lymantria dispar dispar) (Lepidoptera: Erebidae) Population Density as Derived from Counts in Single Milk Carton TrapsOnufrieva, Ksenia S.; Onufriev, Alexey V.; Hickman, Andrea D.; Miller, James R. (MDPI, 2020-10-03)Estimates of absolute pest population density are critical to pest management programs but have been difficult to obtain from capture numbers in pheromone-baited monitoring traps. In this paper, we establish a novel predictive relationship for a probability (spTfer(r)) of catching a male located at a distance r from the trap with a plume reach D.
- Chromosomal evolution in mosquitoes - vectors of diseasesNaumenko, Anastasia Nikolayevna (Virginia Tech, 2017-06-23)The World Health Organization estimates that vector-borne diseases account for 17% of the global burden of all infectious diseases and has identified the mosquito as the most dangerous of all disease-transmitting insects, being responsible for several million deaths and hundreds of millions of cases each year. The study of mosquito genomics provides a deeper understanding of the molecular mechanisms involved in every aspect of vector biology, such as sex determination, host-parasite interaction, ecology, feeding behavior, immunity and evolutionary trends and can be used for the development of new strategies for vector control. We developed the first map of the mitotic chromosomes of the major vector for West Nile fever and lymphatic filariasis, Culex quinquefasciatus. The map was then successfully utilized for mapping of approximately 90% of available genetic markers to their precise positions on the chromosomes. Idiograms were integrated with 140 genetic supercontigs representing 26.5% of the genome. A linear regression analysis demonstrated good overall correlation between the positioning of markers on physical and genetic linkage maps. This will improve gene annotation and help in distinguishing potential haplotype scaffolds and regions of segmental duplications. It will also facilitate identification of epidemiologically important genes that can be used as targets for the vector control and provide a better framework for comparative genomics that will help understanding of the evolution of epidemiologically important traits. In another study, we confirmed the presence of the newly described species, Anopheles daciae, in regions of Russia using molecular data. Although sympatric with its sibling species, Anopheles messeae, five nucleotide substitutions in the internal transcribed spacer 2 of ribosomal DNA can be used to distinguish the morphologically similar species. Chromosome rearrangements have a significant impact on mosquito adaptation and speciation. Using sequencing data in combination with karyotyping, we demonstrated that significant differences in inversion frequencies distinguish An. messeae from An. daciae, suggesting that these inversions are actively involved in adaptation and speciation. It is essential to have reliable toolbox for correct identification of these species and to know their range for future possible malaria outbreaks prevention.
- Efficacies and Second-Year Effects of SPLAT GM™ and SPLAT GM™ Organic FormulationsOnufrieva, Ksenia S.; Hickman, Andrea D.; Leonard, Donna S.; Tobin, Patrick C. (MDPI, 2014-12-23)Mating disruption is the primary control tactic used against the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae) under the gypsy moth Slow the Spread (STS) program. In this paper, we present the results of the multiyear study designed to evaluate a new liquid SPLAT GM™ (ISCA Tech, Riverside, CA, USA) Organic formulation, which is approved by the USDA to meet National Organic Program Standards for use in organic certified farms, for its ability to disrupt gypsy moth mating, and to evaluate the environmental persistence of SPLAT GM™ and SPLAT GM™ Organic formulations. Environmental persistence of the pheromone beyond the year of application is a significant concern since STS relies on trap catch data to evaluate treatment success. The study was conducted in 2007–2012 in forested areas in Virginia and Wisconsin, USA. We observed that SPLAT GM™ Organic reduced gypsy moth trap catch by ≥90% for 10 weeks in a similar manner as SPLAT GM™ and Hercon Disrupt® II (Hercon Environmental, Emigsville, PA, USA). Although we observed persistent effects in all products one year after application, the persistence observed in SPLAT GM™ and SPLAT GM™ Organic was significantly lower than that of Hercon Disrupt® II plastic laminated flakes.
- Forest stand characteristics of Jefferson National Forest that observed gypsy moth defoliation from 2015-2019 in southwestern VirginiaTurner, Brandon (Virginia Tech, 2021-01-27)The gypsy moth (Lymantria dispar L., Lepidoptera: Erebidae) is an invasive forest pest that has greatly impacted oak dominated forest stands in the northeastern United States. The pest, introduced in the 1860s in Massachusetts, has spread significantly north, south, and west. The National Gypsy Moth Slow the Spread (STS) limits its spread by targeting isolated, low-density gypsy moth populations with aerial applications of insecticides and/or pheromones. Other activities by state and federal agencies include conducting aerial and ground-truth surveys of forest stand injury, resulting from gypsy moth defoliation. Annually, thousands of forested acres across the Commonwealth of Virginia are defoliated by gypsy moths. This survey was conducted to compare and identify some forest stand characteristics of infested (outbreak) and uninfested (control) areas of Virginia that could be used to predict further gypsy moth defoliation. All of the research sites were located in southwestern Virginia in close proximity to the Jefferson National Forest. The survey found stand density index, proportions of defoliation per site, and total basal area per acre of preferred host trees with gypsy moth injury to be significant factors in examining forest susceptibility. This research should be continued to further analyze these forest characteristics and help predict where future stand defoliation could occur.
- Ground application of mating disruption against the gypsy moth (Lepidoptera: Erebidae)Onufrieva, Ksenia S.; Hickman, Andrea D.; Leonard, Donna S.; Tobin, Patrick C. (2019-09)The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), is a non-native defoliating insect that continues to expand its range in North America and undergo periodic outbreaks. In management efforts to suppress outbreaks, slow its spread and eradicate populations that arrive outside of the invaded range, aerial deployments of mating disruption tactics and pesticides are generally used. However, in some cases, such as in heavily urbanized areas or other landscapes where aerial deployments are not feasible or permitted, ground applications are required. Ground applications tend to be labour-intensive to ensure adequate coverage. To better inform optimal deployment of ground applications of mating disruption, we measured the effectiveness of a pheromone formulation designed for ground application, SPLAT (R) GM, in forested areas of Virginia from 2011 to 2014 using different dosages and number of point applications. We observed that SPLAT (R) GM applied to the tree trunks at the dosages of 49.4 and 123.6 g AI/ha in 11 x 11 systematic grids (i.e., every 11 m) reduced male trap catch by >90% relative to untreated control plots, which based on previous studies corresponds to >95% reduction in gypsy moth mating success. Our observations suggest that ground applications of gypsy moth mating disruption can be a successful management tool when circumstances require it.
- How to Count Bugs: A Method to Estimate the Most Probable Absolute Population Density and Its Statistical Bounds from a Single Trap CatchOnufrieva, Ksenia S.; Onufriev, Alexey V. (MDPI, 2021-10-13)Knowledge of insect population density is crucial for establishing management and conservation tactics and evaluating treatment efficacies. Here, we propose a simple and universal method for estimating the most probable absolute population density and its statistical bounds. The method is based on a novel relationship between experimentally measurable characteristics of insect trap systems and the probability to catch an insect located a given distance away from the trap. The generality of the proposed relationship is tested using 10 distinct trapping datasets collected for insects from 5 different orders and using major trapping methods, i.e., chemical-baited traps and light. For all datasets, the relationship faithfully (R = 0.91) describes the experiment. The proposed approach will take insect detection and monitoring to a new, rigorously quantitative level. It will improve conservation and management, while driving future basic and applied research in population and chemical ecology.
- Linear relationship between peak and season-long abundances in insectsOnufrieva, Ksenia S.; Onufriev, Alexey V. (PLOS, 2018-02-22)An accurate quantitative relationship between key characteristics of an insect population, such as season-long and peak abundances, can be very useful in pest management programs. To the best of our knowledge, no such relationship has yet been established. Here we establish a predictive linear relationship between insect catch Mpw during the week of peak abundance, the length of seasonal flight period, F (number of weeks) and season-long cumulative catch (abundance) A = 0.41MpwF. The derivation of the equation is based on several general assumptions and does not involve fitting to experimental data, which implies generality of the result. A quantitative criterion for the validity of the model is presented. The equation was tested using extensive data collected on captures of male gypsy moths Lymantria dispar (L.) (Lepidoptera: Erebidae) in pheromone-baited traps during 15 years. The model was also tested using trap catch data for two species of mosquitoes, Culex pipiens (L.) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae), in Gravid and BG-sentinel mosquito traps, respectively. The simple, parameter-free equation approximates experimental data points with relative error of 13% and R2 = 0.997, across all of the species tested. For gypsy moth, we also related season-long and weekly trap catches to the daily trap catches during peak flight. We describe several usage scenarios, in which the derived relationships are employed to help link results of small-scale field studies to the operational pest management programs.
- Persistence of the Gypsy Moth Pheromone, Disparlure, in the Environment in Various ClimatesOnufrieva, Ksenia S.; Thorpe, Kevin W.; Hickman, Andrea D.; Leonard, Donna S.; Roberts, E. Anderson; Tobin, Patrick (MDPI, 2013-01-14)Mating disruption techniques are used in pest control for many species of insects, yet little is known regarding the environmental persistence of these pheromones following their application and if persistence is affected by climatic conditions. We first studied the persistent effect of ground applications of Luretape GM in Lymantria dispar (L) mating disruption in VA, USA in 2006. The removal of Luretape GM indicated that the strong persistent effect of disparlure in the environment reported by previous studies is produced by residual pheromone in the dispensers as opposed to environmental contamination. In 2010 and 2011, we evaluated the efficacy of two formulations, Disrupt II and SPLAT GMTM, in VA and WI, USA, which presented different climatic conditions. In plots treated in WI and VA, male moth catches in pheromone-baited traps were reduced in the year of treatment and one year after the pheromone applications relative to untreated controls. However, similar first- and second-year effects of pheromone treatments in VA and WI suggest that the release rate over one and two years was the same across markedly different climates. Future applications that use liquid or biodegradable formulations of synthetic pheromones could reduce the amount of persistence in the environment.
- Relationship between efficacy of mating disruption and gypsy moth densityOnufrieva, Ksenia S.; Hickman, Andrea D.; Leonard, Donna S.; Tobin, Patrick C. (2018-03-31)Mating disruption tactics involve the deployment of pheromones to interfere with mate finding behaviors in insect populations. This management strategy is the dominant one used against expanding gypsy moth populations in the United States, and historically it has been assumed to be most effective against low-density populations. Operationally, mating disruption is used in areas where the season-long trap catch is <30 males/trap, however the maximum population density at which mating disruption is effective remains unknown. We analysed historical gypsy moth mating disruption treatment data from 2000 to 2010, and used this information to guide the mating disruption field studies conducted from 2012 to 2015 against artificially-created populations of various densities, from 0 to 116 males/trap/day. We observed that mating disruption tactics at a dose of 15g AI/ha were effective against gypsy moth populations with a season-long trap catch of at least 115 males/trap. This research highlights the utility of mating disruption in higher gypsy moth densities than what is currently recommended in management programs.