Browsing by Author "Zhang, Aijun"

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    Ecological and behavioral factors associated with monitoring and managing pink hibiscus mealybug (Hemiptera: Pseudococcidae) in the southern US
    Vitullo, Justin Matthew (Virginia Tech, 2009-06-25)
    The pink hibiscus mealybug (PHM), Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) was investigated with regard to damage caused to hibiscus by feeding, dispersal of nymphs, evaluation of management tactics, and the use of sex pheromone based monitoring in southern Florida from 2005 to 2008. Understanding the ability of PHM to locate and colonize new hosts, and the response of hosts is essential to optimized monitoring and management strategies. Investigation of the onset and severity of PHM feeding symptoms by Hibiscus rosa-sinensis L. showed that severity of symptoms differed among cultivars and that PHM were found on plants that did not exhibit feeding symptoms. Aerially dispersing PHM were predominantly first instars. Dispersal occurred with a diel periodicity that peaked between 14:00 and 18:00 h and was significantly influenced by mean wind speed. Initial infestation with 5, 10, or 20 PHM adult females had no significant affect on the number of dispersing individuals captured from hibiscus plants and PHM were captured at 50 m from infested source plants. The effects of mating disruption, the insecticide (dinotefuran), the parasitoid, Anagyrus kamali (Moursi), and the predator, Cryptolaemus montrouzieri (Mulsant) on PHM on hibiscus plants in screened field cages were evaluated. The total number of mealybugs captured in sticky band and pheromone traps during the study was reduced by dinotefuran and the predator. At the end of the study, the number of nymphs recovered from hibiscus terminals was reduced by the dinotefuran, predator and parasitoid treatments. Field experiments showed that the time of day during which male PHM were captured in pheromone traps in May and September was crepuscular, with most captures occurring from 18:00 to 21:00 h. Significantly more males were captured in traps placed in non-host trees at an elevation of 2 m above the ground than 6 m, and more males were captured in traps placed within host plants than in those 3 m upwind. Pheromone traps placed in hibiscus treated with soil applied dinotefuran or left untreated captured equal numbers of males during the 3 wk prior to treatment and during the 12 wk after treatment. Release of parasitoids at residential sites did not have a significant effect on the total number of males captured in sex pheromone traps over 18 mo. The number of mealybugs found at both parasitoid release and untreated sites were highly variable and corresponded with males captured in sex pheromone traps, as high and low levels of mealybugs corresponded with high and low levels of males captured. The number of males captured in pheromone traps during a two week survey at residential sites in May were a strong predictor of subsequent captures in 2006 (r2 = 0. 712), but not 2007 (r2 = 0.019). The relationship between PHM populations and males captured in sex pheromone traps was influenced by a multitude of factors that can impact the ability of traps to accurately reflect populations at a given location. Pheromone traps have the potential to provide meaningful information towards monitoring and mitigating risk from PHM. The contributions of this dissertation towards optimizing PHM sex pheromone monitoring, as well as facets of PHM monitoring that have yet to be resolved are discussed.
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    Environmental and behavioral factors associated with the infestation of vineyards by larvae of grape root borer
    Rijal, Jhalendra P. (Virginia Tech, 2014-04-03)
    Grape root borer, Vitacea polistiformis (Harris), is an oligophagous pest of grapevines in the eastern USA. Neonates must burrow into the soil to find grape roots. In Virginia, larvae feed on roots for ~2 years, then pupate just beneath the soil surface. Emerging adults leave an empty pupal exuviae at the soil surface around the vine base. There was no relationship between weekly captures in pheromone traps and pupal exuviae counts, indicating that exuviae sampling is most appropriate to assess infestations. Exuviae sampling in Virginia vineyards revealed infestations that ranged from light to very heavy. Eighteen biotic and abiotic variables were measured and used in analyses that assessed their relative contributions to differences in exuviae density. Water holding capacity and clay/sand ratio were most strongly associated with pupal exuviae density; these variables were used to develop a model for predicting the extent of infestation of individual vineyards. The spatial distribution of pupal exuviae was characterized using non-spatial and geospatial techniques. Although the non-spatial method (Taylor's Power Law) indicated that exuviae showed an aggregated distribution in all blocks, spatial methods (variograms, SADIE) revealed aggregated distributions only in blocks with ≥ 0.5 pupal exuviae per vine. Independent pupal exuviae samples for population assessment in vineyards can be achieved using sampling points separated by >8.8 m. Combined results from geospatial analyses and the temporal distribution of pupal exuviae within years enabled the development of a practical and quantitative sampling protocol. Bioassays used to measure the behavioral response of larvae to host stimuli revealed that neonates were attracted to grape root volatiles. In soil column bioassays, larvae moved vertically and horizontally over distances of up to 120 cm and apparently perceived the presence of grape roots from a distance of 5 cm in soil. Results are discussed in relation to their potential implications for monitoring and managing grape root borer.
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    Expression of feeding symptoms from pink hibiscus mealybug (Hemiptera: Pseudococcidae) by commercially important cultivars of hibiscus
    Vitullo, Justin; Zhang, Aijun; Mannion, Catharine; Bergh, J. Christopher (Florida Entomological Society, 2009-06)
    The pink hibiscus mealybug, Maconellicoccus hirsutus (Green), is a highly polyphagous pest that invaded southern Florida in 2002 and is now widely established throughout most of the state. Although Hibiscus rosa-sinensis L. is a preferred and economically important host of M. hirsutus, the susceptibility and expression of feeding symptoms by different cultivars have not been evaluated. Cultivars of H. rosa-sinensis were infested with M. hirsutus and evaluated daily for 40 d for the onset and percentage of terminals expressing feeding symptoms. Under different initial densities of M. hirsutus, the cultivar 'President' showed no difference in the latency to expression of feeding symptoms, which occurred between 7 and 15 d after infestation, but did show significant differences between initial density and percentage of terminals expressing feeding symptoms from 10 d onward. When infested with 20 females, 80% of 'President' terminals exhibited symptoms 30 d after infestation. Four other cultivars initially infested with 10 female M. hirsutus showed significant differences in the onset and severity of feeding symptoms. All plants of the cultivars 'Florida Sunset' and 'Joanne' expressed damage symptoms at 12 +/- 2 SE d and 10 +/- 1 d, respectively, following infestation. Only a single plant of the cultivars 'Double Red' and 'Snow Queen' showed such symptoms at 19 and 30 d after infestation, respectively. Significant differences between cultivar and the percentage of terminals expressing feeding symptoms were observed from 20 d onward. Terminals sampled from all plants after 40 d revealed that egg, nymph, and adult female M. hirsutus were found on all plants, including those that did not exhibit feeding symptoms. These data have shown that hibiscus cultivars differ in their expression of M. hirsutus feeding symptoms, that M. hirsutus can reproduce on cultivars of hibiscus that do not express feeding symptoms, and that feeding symptoms are not a reliable indicator of infestation by M. hirsutus, highlighting the need for further investigation of the mechanisms underlying differences among cultivars.
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    Female sex pheromone of the dogwood borer (DWB), Synanthedon scitula, and attraction inhibitor (antagonist)
    (United States Patent and Trademark Office, 2011-05-17)
    A composition for attracting male Synanthedon scitula, containing a male Synanthedon scitula attracting effective amount of Z,Z-3,13-octadecadienyl acetate, optionally E,Z-2,13-octadecadienyl acetate, optionally Z,E-3,13-octadecadienyl acetate, and optionally a carrier material or carrier; the composition containing less than about 0.3% E,Z-3,13-octadecadienyl acetate based on the molar amount of the Z,Z-3,13-octadecadienyl acetate in the composition. A method for attracting male Synanthedon scitula to an object or area, involving treating an object or area with a male Synanthedon scitula attracting composition containing a male Synanthedon scitula attractant effective amount of Z,Z-3,13-octadecadienyl acetate, optionally E,Z-2,13-octadecadienyl acetate, optionally Z,E-3,13-octadecadienyl acetate, and optionally a carrier material or carrier; the composition containing less than about 0.3% E,Z-3,13-octadecadienyl acetate based on the molar amount of the Z,Z-3,13-octadecadienyl acetate in the composition. A method for inhibiting (antagonizing) male Synanthedon scitula attraction to female Synanthedon scitula, involving exposing a Synanthedon scitula population to a composition containing E,Z-3,13-octadecadienyl acetate in a quantity sufficient to inhibit (antagonize) male Synanthedon scitula attraction to female Synanthedon scitula, and optionally a carrier material or carrier.
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    Plant-insect interactions between female dogwood borer and apple
    Frank, Daniel L. (Virginia Tech, 2009-12-08)
    A rearing methodology for dogwood borer was developed, using standardized procedures at each developmental stage. These methods enabled the establishment of a laboratory colony and efficient production of synchronized cohorts of each of its lifestages throughout the year for specific experimental needs. The behavioral repertoire shown by mated female dogwood borer in an apple orchard was characterized and quantified and the diel periodicity with which those behaviors occurred was determined. Mated females were easily recognized, based on their characteristic casting flight directed toward areas below the graft union of apple trees, and were observed more frequently during the late afternoon and evening. Casting flight, probing with the ovipositor, and oviposition were the most frequent behaviors observed, but the duration of those behaviors was relatively short compared with the much lengthier periods of resting behavior that typically occurred within the canopy. Data from a previous, three-year study in two newly planted apple orchards were subjected to geostatistical analyses to examine the temporal and spatial patterns of infestation by larval dogwood borer and to gain further information about the spatial scales at which oviposition occurs. There were moderate to high degrees of aggregation of dogwood borer infestations on neighboring apple trees, with ranges of spatial dependence from 7.50–19.87 m. No directionality was observed in the spatial autocorrelation of infestation and it appears that females utilized oviposition sites equally along and across orchard rows. The aggregated nature of infestations requires that random, independent samples must be taken from a number of sample pairs at distances greater than the range of spatial dependence to ensure that sample data are not autocorrelated. Alternatively, an efficient sampling program for mapping dogwood borer infestation can be achieved by limiting sample points to distances within the range of spatial dependence. These sample points can be used in interpolating algorithms, such as kriging, to predict infestation at unsampled locations in space for use in site-specific pest management programs. The external morphology of male and female dogwood borer antennae and their sensilla were examined using light and scanning electron microscopy to characterize, measure and compare the types, number, and distribution of sensilla. Although the general shape and size of male and female antennae were similar, those from females possessed a greater number of generally smaller antennal flagellomeres. The flagellum of both male and female antennae contained seven sensillum types including auricillica, basiconica, chaetica, coeloconica, squamiformia, styloconica, and three subtypes of sensilla trichoidea. With the exception of sensilla basiconica, which were present in roughly equal numbers on male and female antennae, all other sensillum types were significantly more abundant on female antennae. The antennae of female dogwood borer appear well equipped to perceive olfactory stimuli, based on the types and number of sensilla present. Coupled gas chromatography and electroantennogram detection (GC-EAD) analyses of headspace collections from damaged and undamaged tissues from apple and dogwood trees were conducted to examine and compare the antennal responsiveness of female dogwood borer to host plant volatiles. A total of 16 and 9 compounds from apple and dogwood tissues, respectively, consistently elicited an antennal response in females. There were no differences in the response of antennae from virgin and mated females, and the amplitude of the female response to host odors was greater than that of males. Six compounds were identified from the headspace collections from apple trees, four of which (octanal, nonanal, decanal, and methyl salicylate) were identified from all apple tissues sampled. A novel compound,α-bergamotene, was identified from injured apple bark, from apple burr knots infested with dogwood borer larvae and from larval dogwood borer frass, and appears to be produced by apple trees in response to injury. Another novel compound, methyl-2,4-decadienoate, was identified from infested burr knot tissue and appears to be produced in response to an insect-plant interaction. Two compounds, hexanoic and nonanoic acid, were identified from headspace collections from dogwood trees. Numerous approaches were used to examine the behavioral response of mated female dogwood borer to host plant headspace collections and to individual compounds from those collections that elicited a strong and repeatable antennal response. Under both natural and semi-natural conditions in the field and in laboratory bioassays, neither attraction/orientation or consistent oviposition were documented and it is apparent that correlating the electrophysiological and behavioral responses of mated female dogwood borer to olfactory stimuli from their host plants will require further research on bioassay development.
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    Semiochemical Production and Laboratory Behavior Response of the Brown Marmorated Stink Bug, Halyomorpha Halys
    Harris, Christina; Abubeker, Sitra; Yu, Mengmeng; Leskey, Tracy C.; Zhang, Aijun (PLOS, 2015-11-03)
    Background The brown marmorated stink bug (BMSB) is an exotic insect pest that was first recognized in the United States in 2001. As of today, it has been found in more than 42 states. BMSB has a very broad host plant range and damage to crops in mid-Atlantic States has reached a critical level. A reliable and accurate tool for infestation detection and population monitoring is urgently needed to provide better and more timely interventions. Pheromones produced by male BMSB have been previously identified and are currently used in BMSB infestation detection. However, the conditions affecting BMSB production of these pheromones were unknown. Methodology/Principal Findings In this study, we collected headspace volatiles from male BMSB under laboratory conditions, measured the temporal patterns of release of these pheromones, and assayed the attractiveness to conspecifics. In addition to the pheromone components, tridecane (C13) and E-2-decenal (an alarm compound) were observed in headspace collections of males, as well as in females and nymphs. Exposure of pheromone-emitting adult males to synthetic C13 greatly reduced pheromone emission. Conclusions/Significance This information should lead to a better understanding of the biology, physiology, and chemical ecology of BMSB, which will help scientists and growers develop more efficient strategies based on natural products to manage BMSB population, therefore, reducing pesticide usage and protecting the crops from BMSB damage.