Browsing by Author "Rijal, Jhalendra P."

Now showing 1 - 3 of 3
  • Thumbnail Image
    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.
  • Thumbnail Image
    Evaluating invasion risk and population dynamics of the brown marmorated stink bug across the contiguous United States
    Illán, Javier Gutierrez; Zhu, Gengping; Walgenbach, James F.; Acebes-Doria, Angel; Agnello, Arthur M.; Alston, Diane G.; Andrews, Heather; Beers, Elisabeth H.; Bergh, J. Christopher; Bessin, Ricardo T.; Blaauw, Brett R.; Buntin, G. David; Burkness, Erik C.; Cullum, John P.; Daane, Kent M.; Fann, Lauren E.; Fisher, Joanna; Girod, Pierre; Gut, Larry J.; Hamilton, George C.; Hepler, James R.; Hilton, Richard; Hoelmer, Kim A.; Hutchison, William D.; Jentsch, Peter J.; Joseph, Shimat V.; Kennedy, George G.; Krawczyk, Grzegorz; Kuhar, Thomas P.; Lee, Jana C.; Leskey, Tracy C.; Marshal, Adrian T.; Milnes, Joshua M.; Nielsen, Anne L.; Patel, Dilani K.; Peterson, Hillary D.; Reisig, Dominic D.; Rijal, Jhalendra P.; Sial, Ashfaq A.; Spears, Lori R.; Stahl, Judith M.; Tatman, Kathy M.; Taylor, Sally V.; Tillman, Glynn; Toews, Michael D.; Villanueva, Raul T.; Welty, Celeste; Wiman, Nik G.; Wilson, Julianna K.; Zalom, Frank G.; Crowder, David W. (Wiley, 2022-11-01)
    BACKGROUND: Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such models have rarely been created for invasive pest species with rapidly expanding ranges. Here, we leveraged a national monitoring effort from 543 sites over 3 years to assess factors mediating the occurrence and abundance of brown marmorated stink bug (BMSB, Halyomorpha halys), an invasive insect pest that has readily established throughout much of the United States. RESULTS: We used maximum entropy models to estimate the suitable habitat of BMSB under several climate scenarios, and generalized boosted models to assess environmental factors that regulated BMSB abundance. Our models captured BMSB distribution and abundance with high accuracy, and predicted a 70% increase in suitable habitat under future climate scenarios. However, environmental factors that mediated the geographical distribution of BMSB were different from those driving abundance. While BMSB occurrence was most affected by winter precipitation and proximity to populated areas, BMSB abundance was influenced most strongly by evapotranspiration and solar photoperiod. CONCLUSION: Our results suggest that linking models of establishment (occurrence) and population dynamics (abundance) offers a more effective way to forecast the spread and impact of BMSB and other invasive species than simply occurrence-based models, allowing for targeted mitigation efforts. Implications of distribution shifts under climate change are discussed.
  • Thumbnail Image
    Grape Root Borer (Lepidoptera: Sesiidae): An Economic Pest of Commercial Vineyards in the Eastern United States
    Rijal, Jhalendra P.; Bergh, J. Christopher (Entomological Society of America, 2017-01)
    Grape root borer, Vitacea polistiformis (Harris; Lepidoptera: Sesiidae) is indigenous to the eastern United States and an economically important pest of commercial vineyards much of that region. After eclosion from eggs laid above ground, the oligophagous larvae burrow into the soil and feed on grape roots for 1-3 yr before pupating and emerging as an adult moth. Compared with many other lepidopteran pests of economic crops, the development of IPM tactics for grape root borer has lagged. Indeed, an important ongoing issue is that grape growers often remain unaware of an infestation until the vines show advanced symptoms. While captures of males in sex pheromone-baited traps can be used to determine the initiation, peak, and cessation of adult flight annually, they are not useful to assess the degree of infestation in individual vineyard blocks. Regular sampling of the pupal exuviae left by emerging adults is the optimal method to assess grape root populations in commercial vineyards. The biology and pest status of grape root borer are reviewed and recent developments toward improved monitoring and management tactics for it are discussed.