The cyst nematode, Globodera pallida, is an obligate, biotrophic pathogen of potato, causing up to 80% yield loss. In the present study, a non-destructive imaging technique was used to compare the development and behavior of G. pallida in its host Solanum tuberosum and in the non-host S. sisymbriifolium. We used microscopy-rhizosphere chambers coupled with the fluorescent stain PKH26, and compared this with destructively sampled acid fuchsin staining. No significant difference (P ≥ 0.90) in G. pallida numbers was found whether stained with PKH26 or acid fuchsin for either plant species indicating no toxic effect from the vital stain. PKH26 labelled J2s successfully located and penetrated roots of both S. tuberosum and S. sisymbriifolium. Two days after inoculation, PKH26 stained G. pallida was clearly observed migrating intercellularly through root tissues of both S. tuberosum and the non-host S. sisymbriifolium. Overall, more nematodes were observed in S. tuberosum than in S. sisymbriifolium roots. No live J2s were observed in S. sisymbriifolium roots stained with either acid fuchsin or PKH26 after 8 days. Understanding the time line of development of G. pallida in S. sisymbriifolium is important towards comprehensive understanding of plant defense responses.
Findings of this research are useful for monitoring the quality of commercial pasteurized milk, particularly in locations where environmental conditions make longer storage difficult. The study also provides valuable information for development of colorimetric shelf life indicators.
Temperature is a critical single factor influencing insect population dynamics, and is foundational for improving our understanding of the phenology of invasive species adapting to new agroecosystems or in the process of range expansion. An age-stage, two-sex life table was therefore developed to analyze fundamental demographic features such as development, survival, and reproduction of a Minnesota-acclimated population of the invasive brown marmorated stink bug (Halyomorpha halys), in the north central USA. All salient life history parameters were estimated to better understand the population growth potential of H. halys at the current limit of its northern range in North America. We examined the effect of selected constant temperatures on immature development and survival (15–39 °C), adult reproduction and longevity (17–36 °C) of H. halys in the laboratory. The Minnesota population developed faster and survived at higher rates relative to a population that had previously established in Pennsylvania, USA. Mean generation time for the Minnesota population was minimized at 30 °C, while survival and fecundity were maximized at 27 and 23 °C, respectively. Given these findings, we assessed the effect of temperature on the intrinsic rate of increase ( r m ), the life table parameter that integrates the effects of temperature on development, survival, and reproduction. A Ratkowsky model predicted r m was maximized (0.0899) at 27.5 °C. We discuss the implications of our findings for understanding population growth rates for H. halys in the context of a warming climate, and potential to emerge as a serious crop pest in the Midwest U.S. region.
Prior studies on species-specific responses to habitat alteration have demonstrated that niche breadth is positively associated with patch occupancy rates in landscapes fragmented by agriculture. However, these studies generally have focused on vertebrates and relied upon data collected at a single point in time, neglecting dynamic processes that could alter inferences. We studied the effects of host selection and forest fragmentation on population dynamics of acorn weevils Curculio, the primary insect seed predators of oaks in North America. Detection/non-detection data were collected from 174 red and white oaks in 19 forested fragments from 2005-2008. We used dynamic multi-season site-occupancy models within a Bayesian framework to explore variation in patch (tree-level) occupancy dynamics of three species of weevils that vary in their specialization, i.e. their relative selection of red and white oak as hosts: C. pardalis (white oak specialist), C. sulcatulus (generalist) and C. proboscideus (generalist). Contrary to expectations, the specialist exhibited greater estimated rates of occupancy than generalists. However, red oak trees occupied by the white oak specialist appeared to function as sink populations maintained by frequent colonization following local extinction. Specialists also exhibited greater relative variation in occupancy and relative abundance on their host trees among years. Generalists exhibited lower local extinction and colonization rates than the specialist. Occupancy and vital rates of weevils on a host tree increased with acorn production and were significantly influenced by neighborhood forest density. Our results suggest that across much of their range in the eastern United States acorn weevils exist in fragmented, temporally dynamic landscapes, with generalists occurring on a lower proportion of usable trees but buffered by access to more suitable patches and greater patch-specific survival. More generally, our results demonstrate that estimates of specialization derived from occupancy data may be misleading in the absence of patch-specific information on vital rates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.