Browsing by Subject "Parasitoid"

Now showing 1 - 4 of 4
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    Cold tolerance of emerald ash borer parasitoids: Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae), Spathius agrili Yang (Hymenoptera: Braconidae), and Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae)
    (2013-05) Hanson, Anthony Arden
    Three Chinese parasitoids are currently being released in North America to control emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae): Spathius agrili Yang (Hymenoptera: Braconidae), Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), and Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae). The degree to which cold climates may limit their potential distributions in North America is unknown, especially in areas like Minnesota that experience a wide range of winter temperatures. To assess parasitoid cold tolerance, I developed a new thermocouple design to reliably measure the temperature of small insects, such as parasitoids. I then exposed the parasitoids to temperatures from 0 to -35°C in the lab to assess their cold tolerance. NAPPFAST software was used to forecast overwintering mortality of S. agrili and T. planipennisi in North America. These forecasts of overwintering mortality will aid researchers and policy makers in deciding where the parasitoids should be released.
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    Flight capacity of emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) and its parasitoid Tetrastichus planipennisi (Hymenoptera: Eulophidae), in response to several experimental treatments
    (2014-12) Fahrner, Samuel Joseph
    Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive beetle native to eastern Asia. Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is one of three hymenopteran parasitoids currently being introduced into North America as part of a classical biological control program against emerald ash borer. Here, custom-built, computer-monitored flight mills were used to measure the effects of age, feeding status, mating status, sex, and size on flight metrics of T. planipennisi. The flight mill was then used to measure flight metrics of emerald ash borer and T. planipennisi across a range of temperatures and relative humidity. The relationship between flight energetics, specifically flight distance, with temperature was then integrated with landscape temperatures at ten locations throughout the continental United States to compare relative dispersal capacity for emerald ash borer and T. planipennisi. The goal of this research was to elucidate factors that mediate the flight capacity of both insects and, for T. planipennisi, to infer the pre- and post-release conditions that may optimize flight capacity.
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    Mind the Gap: the evolution of oviposition site and specialisation in the parasitoid superfamily Chalcidoidea
    (2018-03-05) Boulton, Rebecca A; Heimpel, George E; rebeccaboulton87@googlemail.com; Boulton, Rebecca A
    Parasitoid wasps have contributed significantly to our understanding of ecological specialisation and the evolution of traits linked to host range. Oviposition site is one such trait. Endoparasitoids deposit their eggs inside the host body and tend to be more highly specialised than ectoparasitoids (which lay eggs externally) because they must develop specific strategies to overcome host immune defences. Intermediate to endo- and ectoparasitism is a strategy that we call ‘gap laying’. Gap-laying parasitoids deposit their eggs between the hard outer puparium and the larva of dipteran hosts. This behaviour has received less empirical attention than endo- and ectoparasitism but has important implications for the evolution of specialisation. Using a phylogenetically controlled comparative approach we find that gap-laying species in the hymenopteran superfamily Chalcidoidea exhibit numeric host ranges intermediate to endo- and ectoparasitoids, but these groups exploit a similarly taxonomically related range of hosts. We found that gap-laying can arise from ectoparasitism or endoparasitism, but once it evolves it shows patterns consistent with an evolutionary dead-end compared to other strategies. The results of this study demonstrate how oviposition site, beyond the normal endo-ectoparasitoid dichotomy, influences host specificity, shedding light on the causes and consequences of ecological specialisation in the parasitic Hymenoptera.
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    The Resurgence of Larch Casebearer in the Great Lakes Region
    (2021-06) Stout, Spencer
    Larch casebearer, Coleophora laricella Hübner, (Lepidoptera: Coleophoridae), was discovered infesting eastern larch, Larix laricina (Du Roi) K. Koch, in North America in the 1880s. The insect was likely introduced from Europe on shipments of European larch, Larix decidua Mill., stock. Larch casebearer quickly spread through the range of eastern larch and eventually western larch in western North America. Since 2000, larch casebearer defoliation has increased on these two species of Larix across North America despite previous successful biological control by two introduced parasitoids; Agathis pumila Ratzeburg (Hymenoptera: Braconidae) and Chrysocharis laricinellae Ratzeburg (Hymenoptera: Eulophidae) in the Great Lakes region. I sampled eastern larch at multiple sites across Minnesota and Wisconsin, USA in 2018 and 2019, to determine if these parasitoids were still present. I observed the continued presence of A. pumila and C. laricinellae in both states along with 13 other parasitoid species associated with larch casebearer. Cirrospilus pictus Nees (Hymenoptera: Eulophidae), an historically rare parasitoid, was more abundant than the specialist A. pumila. I also examine whether host species affects the overwintering cold tolerance and spring activation of two allopatric populations of larch casebearer from Minnesota and Idaho. Through a common garden experiment, I determined that the supercooling points and the number of degree days accumulated for spring activation for populations of larch casebearer from Minnesota reared on eastern and western larch were similar, suggesting that differences are not likely due to host species. Instead, the different populations on eastern larch and western larch may be two different species or varying autumnal and winter conditions may affect thermal plasticity and adaptation.