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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The nutritional ecology of a host-parasitoid interaction

Harvey, Jeffrey Alan January 1995 (has links)
No description available.
2

Natural enemies and mortality factors of the coffee leafminer Leucoptera coffeella (Guerin-Meneville) (Lepidoptera: Lyonetiidae) in Chiapas, Mexico

Lomeli-Flores, Refugio 10 October 2008 (has links)
Through field surveys and laboratory experiments, this study assessed in part the impacts of host plant, natural enemies, and weather variables on coffee leafminer Leucoptera coffeella distribution and abundance at two elevations and two rainfall levels in coffee farms in Chiapas, Mexico. In addition, a checklist of Neotropical coffee leafminer parasitoids was assembled from field collections and literature review. Coffee leafminer field incidence was positively correlated with leaf nitrogen content and age, but in laboratory experiments coffee leafminers grew larger, developed faster, and had higher survivorship on leaves with moderate (2.9±0.01%) versus low (2.5±0.04%) or high (3.4±0.01%) nitrogen level, and on tough versus soft leaves. Ovipositional preference was not generally for leaves that maximized offspring performance. Coffee leafminer incidence was higher during the rainy versus dry season, and at low versus high elevation. Shade cover reduced ambient temperatures within coffee farms, but did not significantly affect coffee leafminer incidence. The coffee leafminer predator complex included 16 morphospecies, ~88% of them ants (Formicidae), and contributed >58% of real mortality. Predation rates were higher at high versus low elevation, and under high versus low rainfall. Predation was the main source of coffee leafminer mortality throughout the year, and was highest during the rainy season, when coffee leafminer incidence was highest. Neotropical coffee leafminer parasitoids included 23 species of Eulophidae and seven of Braconidae. In Chiapas, 22 larval parasitoid morphospecies were collected. Egg and pupal parasitoids were not recovered. Parasitism accounted for <10% of real mortality, and rates were 8-10-fold higher at low versus high elevation. Parasitism rates were not significantly influenced by temperature or rainfall. Coffee leafminer oviposited mostly during the night, and less under low versus high temperatures. Average monthly temperature minima, which occur during the night, were generally lower at high (~18°C) versus low (~20°C) elevation farms. The incidence and abundance of coffee leafminer may differ between elevations due to differences in temperature, because at high elevation lower temperatures likely reduced coffee leafminer oviposition, and may have increased its mortality rate as a consequence of longer development time and exposure to natural enemies.
3

Natural enemies and mortality factors of the coffee leafminer Leucoptera coffeella (Guerin-Meneville) (Lepidoptera: Lyonetiidae) in Chiapas, Mexico

Lomeli-Flores, Refugio 15 May 2009 (has links)
Through field surveys and laboratory experiments, this study assessed in part the impacts of host plant, natural enemies, and weather variables on coffee leafminer Leucoptera coffeella distribution and abundance at two elevations and two rainfall levels in coffee farms in Chiapas, Mexico. In addition, a checklist of Neotropical coffee leafminer parasitoids was assembled from field collections and literature review. Coffee leafminer field incidence was positively correlated with leaf nitrogen content and age, but in laboratory experiments coffee leafminers grew larger, developed faster, and had higher survivorship on leaves with moderate (2.9±0.01%) versus low (2.5±0.04%) or high (3.4±0.01%) nitrogen level, and on tough versus soft leaves. Ovipositional preference was not generally for leaves that maximized offspring performance. Coffee leafminer incidence was higher during the rainy versus dry season, and at low versus high elevation. Shade cover reduced ambient temperatures within coffee farms, but did not significantly affect coffee leafminer incidence. The coffee leafminer predator complex included 16 morphospecies, ~88% of them ants (Formicidae), and contributed >58% of real mortality. Predation rates were higher at high versus low elevation, and under high versus low rainfall. Predation was the main source of coffee leafminer mortality throughout the year, and was highest during the rainy season, when coffee leafminer incidence was highest. Neotropical coffee leafminer parasitoids included 23 species of Eulophidae and seven of Braconidae. In Chiapas, 22 larval parasitoid morphospecies were collected. Egg and pupal parasitoids were not recovered. Parasitism accounted for <10% of real mortality, and rates were 8-10-fold higher at low versus high elevation. Parasitism rates were not significantly influenced by temperature or rainfall. Coffee leafminer oviposited mostly during the night, and less under low versus high temperatures. Average monthly temperature minima, which occur during the night, were generally lower at high (~18 oC) versus low (~20 oC) elevation farms. The incidence and abundance of coffee leafminer may differ between elevations due to differences in temperature, because at high elevation lower temperatures likely reduced coffee leafminer oviposition, and may have increased its mortality rate as a consequence of longer development time and exposure to natural enemies.
4

Herbivore behaviour, multitrophic interactions and a lack of wound-induced defence in a member of the Cruciferae

Coleman, Ross Antony January 1996 (has links)
No description available.
5

The effects of pyrethroid insecticides upon parasitic hymenoptera in the cereal ecosystem

Longley, Martin January 1995 (has links)
No description available.
6

LIRIOMYZA LEAFMINERS, ASSOCITED PARASITOIDS AND INSECTICIDE EVALUATION IN SOUTH TEXAS

Hernandez Moreno, Ricardo 2009 May 1900 (has links)
In the Lower Rio Grande Valley of Texas, dipterous leafminers cause damage to pepper crop by destroying small plants (excessive mining), reduction of yield, and by vectoring plant diseases. The objectives of the present research were to identify leafminers species, which cause damage to peppers in South Texas, their associated parasitoid guilds and to evaluate the efficacy of abamectin, novaluron, spinetoram and lambda-cyhalothrin against leafminers as well as their effects on the parasitoid complex. Field surveys were conducted on various pepper varieties in different cities of South Texas. Insecticide evaluation was carried out on field plots in Weslaco TX using the different insecticide treatments and water. To determine the insecticides? lethal effects on adult leafminer parasitoids, Neochrysocharis formosa and Ganaspidium nigrimanus, laboratory bioassays, such as topical insecticide application, pesticide intake and residual effects were performed. The surveys suggested that the leafminers causing the most damage to pepper crops in South Texas is Liromyza trifolii, which represents more than 99% of the collected and identified species. Twenty parasitoid species, of four different families, were found to be attacking L. trifolii on pepper plants in the field. Novaluron was the most effective insecticide in controlling L. trifolii, followed by spinetoram and abamectin. Lambda-cyhalothrin was the least effective, showing L. trifolii tolerance to the compound. In field evaluation novaluron showed the lowest parasitoid: leafminer larvae ratio and parasitoid diversity index. In contrast, novaluron had the least impact on adult parasitoids in laboratory bioassays compared with other treatments (abamectin, spinetoram, lambdacyhalothrin). The lambda-cyhalothrin showed negative effects only to Ganaspidium nigrimanus in topical assays, but in the residual assays it had negative effects on G. nigrimanus as well as N. formosa. On the other hand, abamectin showed negative effects on N. formosa and G. nigrimanus in the topical and intake bioassays and negative effects on G. nigrimanus but no-effect on N. formosa in the residue bioassay. Furthermore spinetoram showed negative effects on N. formosa and G. nigrimanus in all bioassays carried out in the laboratory. Leafminer species, parasitoid species composition, efficacy of insecticides, effects of insecticides on parasitoids and development of tolerance to lambda-cyhalothrin by L. trifolii and N. formosa were discussed.
7

Molecular genetics of host manipulation and competition in an insect parasitoid system / by Markus Hans Beck.

Beck, Markus Hans January 1998 (has links)
Bibliography: leaves 108-128. / ix, 128, [10] leaves, [32] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Maternal protein secretions from the parthenogenetic endoparasitoid wasp Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) were analysed regarding their ability to protect the parasitoid egg against the host immune system. These secretions include nucleic acid-free glycoproteins, called virus-like particles (VLPs) that are produced in the ovarian calyx gland. Results found that VLP-free calyx fluid has the ability to actively suppress host defence reactions, rather than VLPs on the egg surface being solely responsible for the protection of the egg. It was shown the VLP-free calyx fluid contains serine protease-inhibitor activity capable of transiently inhibiting melanogenisis and hemocyte spreading in the host. This indicates that immediately after oviposition the egg surface is not fully protected against host defence reactions. However, at later stages the egg seems to have acquired an immunologically inert surface, and is therefore protected after the suppressive activity of the calyx fluid has disappeared. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1999
8

Studies on parasitoids of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), in South Africa /

Nofemela, Sicelo Robert. January 2004 (has links)
Thesis (M. Sc. (Zoology & Entomology))--Rhodes University, 2004.
9

The relationship between ants (Hymenoptera: Formicidae), vine mealybug (Hemiptera: Pseudococcidae) and parasitoids in vineyards of the Western Cape Province, South Africa /

Mgocheki, Nyembezi. January 2008 (has links)
Dissertation (PhD(Agric)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.
10

Mass rearing of Bracon cephi (Gahan) and B. lissogaster Muesebeck parasitoids of wheat stem sawfly, Cephus cinctus Norton, and temperature-induced mortality in host immatures

Robert, Godshen Robert Pallipparambil. January 2006 (has links) (PDF)
Thesis (M.S.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: David K. Weaver. Includes bibliographical references (leaves 105-112).

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