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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.
41

The epidemiology of wheat streak mosaic virus

Borgman, Robert Peter. January 1959 (has links)
Call number: LD2668 .T4 1959 B68
42

Methoprene as a protectant against five species of stored-product insects in wheat

Zeledon, Manuel E. January 1984 (has links)
Call number: LD2668 .T4 1984 Z44 / Master of Science
43

Effect of delayed sowing and increased crop density on weed emergence and competition with wheat

Gaongalelwe, Motlhasedi Olebile. January 2002 (has links) (PDF)
"July 2002" Bibliography: leaves 40-46.
44

Studies on the ecology of Rhizoctonia solani Kuhn / by Jacobus Frederik de Beer.

De Beer, Jacobus Frederik . January 1965 (has links)
Typescript. / Includes bibliographical references. / 193 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1965
45

The distribution, pathogenicity and population dynamics of Pratylenchus thornei on wheat in South Australia

Nicol, Julie. January 1996 (has links) (PDF)
Bibliography: leaves 224-236. The study aimed to determine the distribution of both P. thornei and P. neglectus in South Australia. Also to study the field and laboratory population dynamics of P. thornei in relation to wheat yields, to determine its host range on a variety of cereal and non-leguminous hosts and to identify possible sources of nematode resistant wheat cultivars/varieties. Preliminary experiments studied the involvement of root rotting fungi with the nematode in wheat disease.
46

Fungal parasitism of cereal aphids in South Africa.

Hatting, Justin Louis. 17 December 2013 (has links)
The Russian wheat aphid, Diuraphis noxia is one of the most destructive exotic invaders of South Africa, capable of reducing individual wheat plant yields by up to 90%. Entomopathogenic fungi are important natural mortality factors associated with this aphid in its Eurasian endemic habitats as well as in the United States and Canada; their impact often exceeding that of predators and parasitoids. The principal objectives of this study included (1) baseline characterization of the aphid-pathogenic flora associated with aphids from South Africa, with special reference to six common cereal aphids, (2) quantification of the comparative impact of the different fungal species on the cereal-aphid complex in three different wheat producing regions of South Africa, (3) field evaluation of the Hyphomycete Beauveria bassiana against D. noxia on resistant wheat, (4) screening of six fungicides for their potential usage in managing entomophthoralean epizootics within greenhouse rearings of the Russian wheat aphid, and (5) development and evaluation of a novel bioassay protocol for screening entomopathogenic Hyphomycetes against D. noxia. A total of nine species of fungi known to infect and kill aphid hosts were collected, including the six entomophthoraleans, Pandora neoaphidis, Conidiobolus thromboides, Conidiobolus obscurus, Entomophthora planchoniana, Conidiobolus coronatus and Neozygites fresenii, and three Hyphomycetes, Beauveria bassiana, Verticillium lecanii, and Paecilomyces farinosus. The former four entomophthoraleans are considered first reports from this country. For the first time, morphological characteristics of these nine South African-collected species are visually depicted and techniques for their isolation and in vitro culture discussed. Seven species of fungi were recorded from D. noxia, of which P. neoaphidis was the most important, causing up to 50% mortality during the late season under dryland conditions in the summer-rainfall region. Mycoses at epizootic levels, together with the large diversity of fungal species recorded from this host, indicated a high level of susceptibility to fungal infection. In contrast, infection of the oat aphid Rhopalosiphum padi remained < 5% despite favourable numbers of hosts and apparently suitable environmental conditions. This phenomenon strongly suggests some level of low susceptibility to fungal infection in this species. Under irrigated conditions m KwaZulu-Natal, the rose-gram aphid Metopolophium dirhodum was the predominant aphid but remained below economical injury levels. Field surveys revealed that this aphid was effectively targeted by P. neoaphidis and C. obscurus, and findings suggest that in some areas of South Africa entomophthoralean fungi effectively suppress this aphid, negating the need for insecticide applications. On average, ca. 61% control of D. noxia on resistant wheat was observed following an application of B. bassiana (5 x 10¹³ conidia per hectare) during the early flag-leaf stage of the wheat. Efficacy of B. bassiana applications on younger plants appeared to be influenced by the level of aphid activity, possibly explained by secondary pick-up of inoculum by D. noxia. These findings accentuate the importance of understanding the tritrophic relationship between host plant, pest and pathogen. The fungicides copper oxychloride, mancozeb + oxadixyl, captab + metalaxyl, bittertanol, iprodione, and mancozeb at a rate of 0.1% active ingredient moderately to strongly inhibited C. thromboides vegetative growth (mean inhibition 81.1 %). Mancozeb at concentrations of 10.0, 2.0, 1.25, 0.5, 0.08, and 0.016% was further evaluated in vitro. The fungus growth cut-off point, midway between 1.25 and 2.0% mancozeb, was calculated and a rate of 1.625% active ingredient per litre of water was used to decontaminate the fungus-infected D. noxia cultures. A novel bioassay protocol was developed, employing live host plants for rearing aphids post inoculation. Using this design against D. noxia, an average LC₅₀ estimate of 85 conidia per mm² for B. bassiana strain GHA was calculated. Control mortality was restricted to levels below 4%. The data indicated high precision due to an average coefficient of variation for slope of less than 20%, and an average chi-squared value of 5.46 ± 2.74 (n = 10 assays). The design will accommodate the use of cereal aphid species other than D. noxia, while live host plants will facilitate tritrophic studies on the effect of host-plant resistance on fungus-induced mortality of D. noxia. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.
47

The distribution, pathogenicity and population dynamics of Pratylenchus thornei on wheat in South Australia / Julie Margaret Nicol.

Nicol, Julie January 1996 (has links)
Bibliography: leaves 224-236. / xiv, 236, [16] leaves, [18] leaves of plates : ill. (chiefly col.), map ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The study aimed to determine the distribution of both P. thornei and P. neglectus in South Australia. Also to study the field and laboratory population dynamics of P. thornei in relation to wheat yields, to determine its host range on a variety of cereal and non-leguminous hosts and to identify possible sources of nematode resistant wheat cultivars/varieties. Preliminary experiments studied the involvement of root rotting fungi with the nematode in wheat disease. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1997
48

Interrelationships between soil-borne pathogens on `Triticum aestivum` / by Bharati K. Patel

Patel, Bharati K. January 1983 (has links)
Bibliography: leaves 172-180 / vi, 180 leaves, [29] 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. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1983
49

Minimum cultivation and root diseases of wheat / by Stephen Michael Neate

Neate, Stephen Michael January 1984 (has links)
Bibliography: leaves 133-144 / viii, 144 leaves, 16 leaves of plates, [3] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1984
50

Resistance in `Triticum aestivum` to infection by `Gaeumannomyces graminis` var `Tritici` / by L. Penrose

Penrose, L (Lindsay) January 1985 (has links)
Bibliography: leaves 141-145 / vii, 145 leaves, [4] leaves of plates : ill. (4 col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Depts. of Plant Pathology and Agronomy, 1986

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