• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 114
  • 31
  • 15
  • 9
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 181
  • 109
  • 105
  • 90
  • 72
  • 61
  • 52
  • 49
  • 30
  • 30
  • 28
  • 25
  • 25
  • 23
  • 23
  • 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

Insect bioelectrostatics and autodissemination of Metarhizium anisopliae (Metsch.) for the biological control of the house-fly (Musca domestica L.)

McGonigle, Daniel Frederick January 2002 (has links)
No description available.
2

Development of formulations and delivery systems to control economically important ticks with entomopathogenic fungi

Nchu, Felix 03 December 2009 (has links)
Due to the rapid development of tick resistance to synthetic chemical acaricides and the potential risk posed by these chemicals to non-target species, efforts are intensifying towards the development of entomopathogenic fungi as an environmentally benign alternative tick control strategy. The main objective of this study is the development of formulations and delivery systems for control of ticks with entomopathogenic fungi. Screening of entomopathogenic fungal isolates is the first step towards the development of mycoacaricides. Twelve isolates of Metarhizium anisopliae (Metschnik.) Sorok. and three isolates of Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) were evaluated for pathogenicity against unfed Rhipicephalus pulchellus Gerstäcker (Acari: Ixodidae) adults under laboratory conditions. Out of the 15 isolates screened, 4 isolates were virulent against R. pulchellus, inducing significantly (F value = 11.86; DF = 14, 75; P < 0.0001) higher tick mortalities; i.e. ICIPE 78 (76.1 ± 5.9%), ICIPE 69 (62.6 ± 5%), ICIPE 62 (49.8 ± 5.8%) and ICIPE 60 (49.6 ± 7.7%), four weeks post-treatment compared to the others. The results of this study demonstrate that R. pulchellus ticks were susceptible to some M. anisopliae isolates. Since the process of strain selection is an important step in the development of insect pathogens for biological control, an appropriate bioassay technique for infecting different life stages of a host is of paramount importance. Bioassays were conducted in the laboratory to evaluate the efficacy of different methods of inoculation using R. pulchellus as a model. In a preliminary experiment, an oil-based formulation of M. anisopliae titred at 109 conidia ml-1 was applied to R. pulchellus adults using a Burgerjon spray tower or a microapplicator. Inoculation by microapplicator yielded poor results (25.0% tick mortality) compared to Burgerjon’s spray tower (52.3% tick mortality) , although the mean number of fungal conidia on R. pulchellus adults was lower (1.5 x 104 ± 1.1 x 103 conidia ml-1) after spraying by Burgerjon’s spray tower compared to 1 x 106 conidia ml-1 obtained with the microapplicator. Thus, inoculation by Burgerjon’s spray tower was selected for further investigations. Different modes of inoculation were tested and included direct spray of inoculum on the tick and substrate (SS), direct spray on the substrate and tick followed by transfer of the tick to clean uncontaminated Petri dish (SP) or indirect inoculation of ticks through substrate (SW). The LC50 values following contamination of nymphs (LC50 = 1.4 x 107 conidia ml-1) and adults (LC50 = 6.7 x 107 conidia ml-1) in SS were significantly lower compared to SP; nymphs (LC50 = 5.7 x 108 conidia ml-1) and adults (LC50 = 5.3 x 109 conidia ml-1) and SW; nymphs (LC50 = 5 x 108 conidia ml-1) and adults (LC50 > 1010 conidia ml-1). Although the LC50 value in SS was the lowest, it recorded the highest tick mortality among control ticks (24.2% at two weeks post-treatment) and (23.3% at three weeks post-treatment) in nymphs and adults respectively compared to SP (2.5 and 5.8% respectively) and SW (0.0 and 0.0). Results show that among the modes of contamination tested, SP was the most appropriate for contaminating R. pulchellus adults. SW and SP were identified as appropriate techniques for infecting the R. pulchellus nymphs with conidia formulated in oil. The integrated use of semiochemicals and entomopathogenic fungus (hypocreales) may optimise the performance of a fungus as a biocontrol agent against ticks. Initially, experiments were conducted to evaluate the attraction of the hunter tick Amblyomma variegatum Fabriscius (Acari: Ixodidae) to semiochemicals. In one of the experiments, the simultaneous release of 1-octen-3-ol and AAAP together with CO2 from a trap in simulated field plots attracted up to 94 ± 6% of adult ticks from a distance of 6 m, and up to 24.0 ± 5.1% from 8 m. Formulations of M. anisopliae (dry powder, oil, and emulsifiable) applied within the trap baited with AAAP and 1-octen-3-ol resulted in high levels of contamination of the ticks attracted to the traps. However, 48 hr after autoinoculation, 89.1 and 33.3% of conidia were lost in dry powder and oil formulations, respectively. Emulsifiable formulation lost the lowest number of propagules (17.1%). Samples of ticks attracted to the baited traps were transferred to plastic basins containing grass and maintained for 5 weeks. The experiment was conducted in the rainy and dry seasons. The emulsifiable formulation gave the highest relative reduction in tick numbers in both seasons: 54.7 and 46.5% in the rainy and dry seasons, respectively, followed by the oil formulation (32 and 23.8%) and the powder formulation (38.0 and 24.4%). Following the high attraction and contamination of A. variegatum under semi-field conditions, experiments were done to evaluate the efficacy of M. anisopliae-treated semiochemical-baited traps for control of A. variegatum under field conditions. Unfed A. variegatum adults (118) were seeded in each 100-m plot. An emulsifiable formulation of M. anisopliae (consisting of 49.5% sterile distilled water, fungal conidia, 49.5% corn oil [CHEF cooking oil, Premier Oil Mills LTD] and 1% Tween 80) titrated at 109 conidia ml-1- was applied in a semiochemical-baited traps (900 cm2) which were placed at 5 spots within the plot. The control and fungal treatments were repeated after 14 and 28 days soon after rotating the traps clockwise (45o) in order to cover different sections of the plot. In the control plots, traps baited with semiochemicals only were used. Six weeks after the initiation of the experiments, five semiochemical-baited traps (untreated) were deployed in each plot for 3 successive days to trap ticks in the treated and control plots. The percentage of ticks recovered in the fungus-treated plots were significantly lower (31.1 ± 5.2%) than in the control plots (85.6% ± 3%) (P < 0.001), which represented a relative tick reduction of 63.7%. Mortality of 93.8 ± 2.3% was observed among the ticks that were recovered from the field and maintained in the laboratory for two weeks; while only 3.3 ± 0.9% died from the control plots. The results of this study open up the possibility of developing an environmentally friendly, low cost product to control these economically important ticks. / Thesis (PhD)--University of Pretoria, 2009. / Paraclinical Sciences / unrestricted
3

Efficacy of Entomopathogenic Nematodes and Entomopathogenic Fungi against Masked Chafer White Grubs, Cyclocephala spp. (Coleoptera: Scarabaeidae)

Wu, Shaohui 07 May 2013 (has links)
Entomopathogenic nematodes (EPN) (Heterorhabditis bacteriophora and H. megidis) and entomopathogenic fungi (EPF) (Metarhizium anisopliae and Beauveria bassiana) were evaluated for efficacy against masked chafer white grub, Cyclocephala spp., under laboratory and greenhouse conditions, as well as their efficacy against various grub stages in the field.  Under both laboratory and greenhouse conditions, additive interactions were found between EPN and EPF in their combined application against Cyclocephala spp., except a few observations that showed antagonism or synergism.  Significantly greater control occurred from the combination of a nematode and a fungus compared with a fungus alone, but not compared with a nematode alone.  The combined effect did not differ significantly for nematode and fungi applied simultaneously or at different times.  EPF had no significant impact on EPN infection and production of infective juveniles (IJs) in grub carcasses.  Nematodes alone or in combination with fungi were comparable to the insecticide Merit 75 WP (imidacloprid) against 3rd instar Cyclocephala spp in the greenhouse. Efficacy of EPF and EPN varied dramatically between field sites and conditions; EPN and EPF applied alone or in combination were less effective than Merit 75 WP in >50% field trials, but some EPN + EPF treatments were more effective than the insecticide in reducing grub numbers.  EPN and EPF showed better potential than insecticides for providing extended control of white grubs in the subsequent generation.  In addition, the sub-lethal effects of EPF on southern masked chafer, C. lurida, were investigated.  Neither M. anisopliae nor B. bassiana had a sub-lethal effect on grub weight gain, adult longevity, oviposition, pupation and eclosion.  Finally, interaction between H. bacteriophora and M. anisopliae was examined to determine the potential of the nematode in improving fungal distribution in soil.  H. bacteriophora enhanced fungal distribution in sandy loam soil without grass thatch, but not in sandy soil with thatch.  In both soil types, soil depths significantly affected nematode and fungal distribution. In water profile, M. anisopliae conidia germinated hyphae that attached to sheath of H. bacteriophora IJs, which molted to detach from the fungus.  IJs mortality and virulence were not affected by the presence of M. anisopliae. / Ph. D.
4

Development of formulations and delivery systems to control economically important ticks with entomopathogenic fungi

Nchu, Felix. January 2009 (has links)
Thesis (PhD (Paraclinical Sciences, Veterinary Science))--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.
5

Evaluation of Metarhizium anisopliae mycoinsecticide as an alternative locust control measure in southern Africa

Müller, Elizabeth Johanna. January 2000 (has links)
Thesis (M.Sc.(Zoology and Entomology))--University of Pretoria, 2000. / Abstracts in Afrikaans and English. Includes bibliographical references (leaves 72-79).
6

Study of Conidia production and transmission of Beauveria bassiana (Balsamo) Vuill. in Colorado potato beetle (Leptinotarso decemlineata) /

Fernandez, Silvia, Groden, Eleanor. Drummond, Francis A. Annis, Seanna L. Lambert, David. Vandenberg, John D. January 2001 (has links)
Thesis (Ph. D.) in Biological Sciences--University of Maine, 2001. / Includes vita. Advisory Committee: Eleanor Groden, Assoc. Prof. of Entomology, Advisor; Francis Drummond, Prof. of Insect Ecology; Seanna Annis, Asst. Prof. of Mycology; David Lambert, Assoc. Prof. of Plant Pathology; John D. Vandenberg, Research Entomology, USDA-ARS. Includes bibliographical references (leaves 158-175).
7

A preliminary report on an integrin-like protein in protoplasts of the entomopathogenic fungus Entomophaga aulicae /

Li, Bing, January 2002 (has links)
Thesis (M.Sc.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 75-86.
8

Study of anti-cancer effect of winter worm and summer grass on Mcf-7 human breast cancer cells

Xu, Tongtong, January 2008 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 9, 2009) Includes bibliographical references.
9

Fitness costs of symbiont switching using entomopathogenic nematodes as a model

McMullen, John G., Peterson, Brittany F., Forst, Steven, Blair, Heidi Goodrich, Stock, S. Patricia 17 April 2017 (has links)
Background: Steinernematid nematodes form obligate symbioses with bacteria from the genus Xenorhabdus. Together Steinernema nematodes and their bacterial symbionts successfully infect, kill, utilize, and exit their insect hosts. During this process the nematodes and bacteria disassociate requiring them to re-associate before emerging from the host. This interaction can be complicated when two different nematodes co-infect an insect host. Results: Non-cognate nematode-bacteria pairings result in reductions for multiple measures of success, including total progeny production and virulence. Additionally, nematode infective juveniles carry fewer bacterial cells when colonized by a non-cognate symbiont. Finally, we show that Steinernema nematodes can distinguish heterospecific and some conspecific non-cognate symbionts in behavioral choice assays. Conclusions: Steinernema-Xenorhabdus symbioses are tightly governed by partner recognition and fidelity. Association with non-cognates resulted in decreased fitness, virulence, and bacterial carriage of the nematode-bacterial pairings. Entomopathogenic nematodes and their bacterial symbionts are a useful, tractable, and reliable model for testing hypotheses regarding the evolution, maintenance, persistence, and fate of mutualisms.
10

Epizootiology and Phylogenetics of Entomopathogenic Fungi Associated with Fiorinia externa ferris(Hemiptera: Diaspididae) in the Northeastern USA

Marcelino, Jose A. P. 10 December 2007 (has links)
The eastern hemlock [Tsuga canadensis (L.) Carrière] is one of the native dominant forest components of northeastern US. At present, these valuable stands face an alarming decline, in part due to the Fiorinia externa, elongate hemlock scale (EHS), (Hemiptera: Coccoidea: Diaspididae). The armored shield of F. externa provides an excellent defense against insecticides, natural enemies and adverse conditions. Chemical and classical biocontrol methods have been unable to stop the spread of this pest. Recently, the occurrence of an epizootic within the F. externa population in the Mianus River Gorge Preserve in Bedford, NY revealed a promising opportunity for control of this scale. Entomopathogenic fungi represent a valuable, although under-utilized, group of organisms with unique capabilities for self-sustaining pest management. Given the significant impact of this epizootic on F. externa, we have conducted extensive research on the biology, genetics and biological control potential of this epizootic. We molecularly identified a complex of entomopathogenic, phytopathogenic, and endophytic fungi associated with the epizootic in 36 localities within the states of New York, Pennsylvania, Connecticut and New Jersey. One fungus, Colletotrichum sp., was the most commonly isolated organism in populations of F. externa within areas of the epizootic. The host range of this Colletotrichum species comprised both insects and plants, although diverse life cycles occured in the different hosts. Endophytic growth was observed in 28 species of plants comprising 18 families (52% of the sampling), whereas in F. externa biotrophic and necotrophic growth was detected. Colletotrichum is a widely known phytopathogenic genus and reports of entomopathogenic activity are extremely rare. In order to understand the biological processes involved in the host-pathogen interactions we quantified the pathogenicity and virulence of this Colletotrichum sp. to four insect families and six plants families as well as the occurrence of sexual recombination in this Colletotrichum sp., both in vitro and in planta. We observed that this Colletotrichum sp. displays a propensy to induce rapid disease and mortality in F. externa hosts. Phylogenetic analysis comprising six of the most commonly studied nuclear genes in molecular phylogenetics (D1/D2 domain of the 28 rDNA gene, ITS region, β-Tubulin 2, GPDH gene, GS gene and HMG box at the MAT1-2 mating-type gene) and RAPDs showed this fungus is closely related to phytopathogenic strains of Colletotrichum acutatum and that it may represent a single population lineage of this species (i.e., Colletotrichum acutatum forma specialis fiorinia). Though a large body of information exists regarding the phytopathogenic genus Colletotrichum, ours is only the second reported entomopathogenic strain. It is not clear whether the colonization of an insect by this fungus is truly rare or a common but undetected event. Sexual recombination, observed in planta and in vitro, could be the means by which new genetic variants are generated leading to new biotypes with a selective advantage to colonize new hosts, which in this case is a novel host in a different kingdom.

Page generated in 0.0668 seconds