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Weevil (Notaris bimaculatus) Feeding Reduces Effectiveness of Glyphosate on Quackgrass (Agropyron repens)
- Philip H. Westra, Donald L. Wyse, Edwin F. Cook
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- Journal:
- Weed Science / Volume 29 / Issue 5 / September 1981
- Published online by Cambridge University Press:
- 12 June 2017, pp. 540-547
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The life cycle of Notaris bimaculatus Fab. and the influence of this weevil on the control of quackgrass [Agropyron repens (L.) Beauv.] with glyphosate [N-(phosphonomethyl) glycine] were studied. Observations on this insect in 1978 and 1979 showed that its life cycle occurs in close association with quackgrass. The adult weevils feed on quackgrass culms and caryopses and use the inside of the culms for ovipositing. Adult populations, measured in quackgrass infestations during the summer months, ranged from 3 to 44/25 sweeps of an insect net. Larvae emerge from the eggs after 2 weeks, feed down the inside of the culms, chew an exit hole, and move into the soil where they attack the rhizomes. Larval numbers ranged from two to six/28 dm3 of soil during the summer months. Larvae feed on the rhizome surface or enter the rhizomes where they devour the vascular and cortical tissue. In dense quackgrass sods treated with glyphosate at 1.7 kg/ha, feeding damage on quackgrass rhizomes caused by the larvae reduced the control of quackgrass by disrupting the translocation of glyphosate in the rhizomes. Although soil-borne larvae of several insects were found in quackgrassinfested soil, larvae of N. bimaculatus were always present. Controlling these soil-borne insect larvae with a soil-applied insecticide for 2 months before applying glyphosate resulted in significantly increased quackgrass control. Shoot regrowth several months after the application of glyphosate at 1.4 kg/ha to quackgrass grown in cages infested with 400 adult weevils was 298 and 611 shoots/m2 in the 1979 and 1980 experiments, respectively. Similar glyphosate applications to weevil-free quackgrass resulted in only 26 and 15 shoots/m2 in the 1979 and 1980 experiments.
15 - Sustainable inland fisheries – perspectives from the recreational, commercial and subsistence sectors from around the globe
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- By Steven J. Cooke, Carleton University, Vivian M. Nguyen, Carleton University, John M. Dettmers, Great Lakes Fishery Commission, Robert Arlinghaus, Humboldt University, Michael C. Quist, University of Idaho, Denis Tweddle, South African Institute of Aquatic Biodiversity, Olaf L. F. Weyl, South African Institute of Aquatic Biodiversity, Rajeev Raghavan, St. Albert's College, Marcela Portocarrero-Aya, Instituto de Investigación de Recursos Naturales Alexander von Humboldt, Edwin Agudelo Cordoba, Instituto Amazónico de Investigaciones Científi cas SINCHI, Ian G. Cowx, University of Hull
- Edited by Gerard P. Closs, University of Otago, New Zealand, Martin Krkosek, University of Toronto, Julian D. Olden, University of Washington
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- Book:
- Conservation of Freshwater Fishes
- Published online:
- 05 December 2015
- Print publication:
- 03 December 2015, pp 467-505
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Summary
INTRODUCTION
Globally, freshwater ecosystems provide varied fishing opportunities (herein termed inland fisheries) represented by three sectors: recreational, commercial and subsistence fisheries. From the depths of the Laurentian Great Lakes to the shallow floodplains of the Ganges River, and from under-ice fisheries in Scandinavia to the rice fields of Southeast Asia, fish and other aquatic life are omnipresent components of fluvial and lacustrine systems. Freshwater fishes generate many ecosystem services that extend beyond their use in fisheries (Holmlund & Hammer, 1999; Cowx & Portocarrereo, 2011). Given the diversity of freshwater fish assemblages, levels of fisheries productivity, cultural norms, density of human population and socioeconomic conditions, it is not surprising that there is immense variation in how, why and the extent to which freshwater fishes and other aquatic animals are exploited. Whether it be sustaining livelihoods through the provision of essential nutrients, generating income, or enabling leisure time with family, inland fisheries are important. Although there are accepted definitions for the three fishing sectors (i.e. UN FAO – see below), ambiguities and exceptions remain that complicate appraisal and management.
Compared with marine waters where industrial-scale commercial fisheries predominate, inland fisheries tend to be smaller in scale and catches generally do not enter the global marketplace. Moreover, whereas exploitation pressures are the primary threat facing marine fish populations and marine ecosystems, in inland systems there are multiple threats including many unrelated to fishing (Arlinghaus et al., 2002). Indeed, declines in freshwater fish fauna are implicated with broad-scale economic activities such as flow regulation, hydropower, agriculture, urbanisation and pollution (Limburg et al., 2011; Chapters 4 and 9). Reflecting the multiple threats, freshwater fishes are among the most imperilled taxa on the globe (Strayer & Dudgeon, 2010; Chapter 2), freshwater biodiversity is in crisis (Dudgeon et al., 2006) and freshwater ecosystems are among the most altered (Kennish, 2002; Malmqvist & Rundle, 2002). Despite the many threats to inland fishes and fisheries, they receive disproportionally less interest and attention from the global conservation community and international political spheres. Indeed, global capture statistics underrepresented inland fisheries and their contribution to global production (Welcomme et al., 2010; Welcomme, 2011a,b), partly because of the diffuse nature of inland fisheries (Beard et al., 2011). By contrast, it is comparatively easy to generate data for commercial fisheries where products sold on established domestic and export markets can be readily monitored.
The louse populations of some cricetid rodents*
- Edwin F. Cook, James R. Beer
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- Journal:
- Parasitology / Volume 45 / Issue 3-4 / November 1955
- Published online by Cambridge University Press:
- 06 April 2009, pp. 409-420
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In 1952 and 1953, 798 specimens of Peromyscus maniculatus, Microtus pennsylvanicus and Clethrionomys gapperi were examined for total louse populations. Two species of sucking lice, Hoplopleura acanthopus and H. hesperomydis, were found on these species. H. acanthopus was found almost exclusively on Microtus pennsylvanicus and Clethrionomys gapperi, and Hoplopleura hesperomydis was found almost exclusively on Peromyscus maniculatus.
Contamination appears to account for the apparently abnormal associations. The rates of infestation varied from host to host and from year to year. In general the higher infestations were found on host populations which were stable or declining, and the lower rates were on hosts which were increasing in density. Microtus pennsylvanicus had the highest infestation rate followed by Peromyscus maniculatus, with Clethrionomys gapperi nearly free of lice.
The age of the host apparently had little to do with rate of infestation or population size.
The louse populations were made up of about equal numbers of adults and nymphs. The adult sex ratio was, in each sample, unbalanced in favour of the females.
The average population size varied between sexes of host and years. The male hosts had a higher average population than the female.
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