Dissertations / Theses on the topic 'Lettuce, Diseases and pests'
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Kerns, David L., and Tony Tellez. "Tank Mixing New Insecticide Chemistries with a Pyrethroid Insecticide for Control of Lepidopterous Pests in Head Lettuce, 1997." College of Agriculture, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/221679.
Full textSultan, Youneskhan 1957. "Rhythm of zoospore production of pythium on lettuce cultured hydroponically." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276687.
Full textMercier, Julien. "Studies of the phylloplane microflora of lettuce and its interactions with pesticides and Sclerotinia sclerotiorum." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65425.
Full textGracia, Javier. "Lettuce stunt : effect of Pythium populations and interactions between Pythium tracheiphilum and nematodes." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59387.
Full textTchervenivanova, Eli. "Development of a model to predict sporulation of Bremia lactucae in lettuce." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23943.
Full textToussaint, Vicky. "Ecology of Xanthomonas campestris pv. vitians in relation to development of bacterial leaf spot of lettuce by Vicky Toussaint." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37850.
Full textCarignan, Sylvie. "Evaluation of the potential of the exotic larval parasitoid Peristenus digoneutis Loan as a biological control agent against the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), in lettuce and celery crops in muck soils of southwestern Quebec." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23387.
Full textPretorius, Rudolph Johannes. "A plant health management system for aphididae on lettuce under variable shadehouse conditions in the central Free State, South Africa." Thesis, Bloemfontein : Central University of Technology, Free State, 2008. http://hdl.handle.net/11462/114.
Full textAphids (Hemiptera: Aphididae) are amongst the most destructive insects in agricultural crop production systems. This reputation stems from their complex life cycles which are mostly linked to a parthenogenetic mode of reproduction, allowing them to reach immense population sizes within a short period of time. They are also notorious as important and efficient vectors of several plant viral diseases. Their short fecund life cycles allow them to be pests on crops with a short growth period, e.g. lettuce (Lactuca sativa L.). It is common practice to provide this crop with some degree of protection from environmental extremes on the South African Highveld. Shadehouses are popular in this regard, but aphids are small enough to find their way into these structures, and their presence on lettuce is discouraged due to phytosanitary issues. In addition, the excessive use of insecticides is criticized due to the negative influence on human health, and because aphids can rapidly develop resistance. This necessitates the use of alternative control options in order to suppress aphid numbers. Biological control is popular in this regard and the use of predatory ladybirds (Coleoptera: Coccinellidae) is a popular choice. This study investigated the aphid and coccinellid species complex encountered under varying shadehouse conditions on cultivated head lettuce in the central Free State Province (South Africa). Their seasonality was also examined, along with variations in their population size throughout a one-year period. Finally, the impact of varying aphid populations on some physical characteristics of head lettuce was examined, and recommendations for aphid control (using naturally occurring coccinellid predators) were made. Two shadehouse structures were evaluated during this study. One was fully covered with shade netting and designed to exclude the pugnacious ant, Anoplolepis custodiens (Hymenoptera: Formicidae), while the other was partially covered with shade netting (on the roof area) allowing access to the ants. Six cycles of head lettuce were planted and sampled four times during each cycle. These were scheduled to monitor the seedling, vegetative and heading stage of lettuce. Four important aphid species were recorded on the lettuce, namely Acyrthosiphon lactucae, Nasonovia ribisnigri, Myzus persicae and Macrosiphum euphorbiae. Both structures harboured similar aphid and coccinellid species, but their population dynamics differed. A. lactucae dominated in the absence of A. custodiens in the fully covered structure (whole study), while N. ribisnigri dominated in the partially covered structure in the presence of these ants during the warmer months (December – January). M. euphorbiae replaced this species as the dominant species in the absence of A. custodiens (April – September). M. persicae occured during the winter (May – August) in the fully covered structure. Promising coccinellid predators were Hippodamia variegata and Scymnus sp. 1, and to a lesser extent, Exochomus flavipes and Cheilomenes lunata. However, the fully covered structure hampered the entrance of the larger adult coccinellid species, resulting in their lower occurrence. Aphid and coccinellid activity peaked during the summer months (October – January), and the fully covered structure attained the highest aphid infestation levels and coccinellid larval numbers during this time. On the other hand, aphid numbers were higher in the partially covered structure during the cooler months of the year (April – July) and this structure also harboured more adult coccinellids. In most cases, aphid infestation levels did not affect the amount of leaves formed. However, symptomatic damage in terms of head weight reduction did occur under severe infestation levels. Specific environmental conditions within a shadehouse structure concurrently contributed to this reduction, with less favourable conditions accelerating this condition. Results from this study have shown that even though the type of shadehouse structure does not influence the insect species complex found on lettuce, it does have an influence on detrimental and beneficial insect population dynamics. Aphid species infesting lettuce have been identified, along with coccinellid predators that could potentially be used in their control. Both types of structures had advantages and disadvantages, and therefore, decisions concerning shadehouses should not be focused on which type of structure to use, but rather which type of structure to use during different seasons of the year.
Trembley, Marcella L. "The effect of mechanical weed cultivation on crop yield and quality, disease incidence and phenology in snap bean, carrot and lettuce crops." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0003/MQ29801.pdf.
Full textGumede, Halalisani. "The development of a putative microbial product for use in crop production." Thesis, Rhodes University, 2008. http://eprints.ru.ac.za/1352/.
Full textUbalijoro, Eliane. "Characterization of resistance to lettuce mosaic virus in Lactuca sativa." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22821.
Full textSingh, Rampal. "Characterization of virus disease resistance in Lactuca sativa." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55529.
Full textTellez, Tony, and David L. Kerns. "Commercial Evaluation of Proclaim for Control of Lepidopterous Pests of Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/221607.
Full textDufresne, Philippe J. "Development and validation of molecular markers for the detection of disease resistance alleles in Lactuca sativa." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78352.
Full textTerry, Alan J. "Control of pests and diseases." Thesis, University of Surrey, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505965.
Full textPalumbo, J. C., C. H. Jr Mullis, and F. J. Reyes. "Comparative Effectiveness of Bacillus thuringiensis Formulations Against Lepidopterous Pests of Fall Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1992. http://hdl.handle.net/10150/214515.
Full textKerns, David L., and Tony Tellez. "Commercial Evaluation of Confirm for Control of Lepidopterous Pests of Lettuce using Various Applications Techniques." College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/221608.
Full textSuzuki, Gerson Shinya [UNESP]. "Comportamento de genótipos de alface com o alelo mo10 ao Lettuce mosaic virus e Lettuce mottle virus." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/113793.
Full textA alface (Lactuca sativa L.), pertencente à família Asteraceae, é uma das hortaliças mais consumidas no Brasil. Um dos principais problemas fitossanitários para essa cultura são as fitoviroses, em especial o Lettuce mosaic virus (LMV), que causa elevados prejuízos aos produtores em diversas regiões do país, além do Lettuce mottle virus (LeMoV), que vem crescendo em importância nos últimos anos. Como forma de controle, o uso de variedades resistentes é maneira mais eficaz de contornar os danos causados por vírus. Na maioria das variedades resistentes de alface faz-se o uso de genes recessivos, em sua maioria envolvidos na interação planta-vírus, são os chamados codificadores de fatores de iniciação de tradução eucarióticos (eIFs). Diante disso, este trabalho teve como objetivo avaliar dois genótipos de alface (169501 e 169501C), quanto a resistência ao LMV e ao LeMoV. Foram realizadas transmissões via extrato vegetal nos dois genótipos de alface com LMV e LeMoV em diferentes intervalos de tempo. Para LMV também foram realizadas transmissões por afídeos. As duas variedades testadas se mostraram resistentes ao LMV nas duas formas de transmissão, mas apresentaram sintomas quando inoculadas com LeMoV. Em reações de RT-PCR com oligonucleotídeos específicos, foram comprovadas a ausência de LMV e a infecção por LeMoV nas plantas inoculadas. O isolado de LMV após análise do sequenciamento da porção N’ terminal da ...
Lettuce (Lactuca sativa L.) belongs to the Asteraceae family and is one of the most consumed vegetables in Brazil. One of the major disease problems in this crop are plant viruses, especially the Lettuce mosaic virus (LMV) that cause losses to producers in various regions of the country, but also Lettuce mottle virus (LeMoV). As a form of control, the use of resistant varieties is the most effective way to overcome the damage caused by plant viruses. Most of the resistant varieties of lettuce makes the use of recessive genes, mostly involved in plant-virus interactions and characterized as eukaryotic translation initiation factor (eIFs). Thus, this study aimed to evaluate two lettuce genotypes (169501 and 169501C) for resistance to LMV and LeMoV. LMV and LeMoV were sap transmitted at different time of intervals. For LMV also transmissions with aphids were carried out. The two varieties tested were resistant to LMV in both forms of transmission, but showed symptoms when inoculated with LeMoV. In RT-PCR with specific primers, LMV was not detected but LeMoV yes, confirming the infection in the inoculated plants. The isolate of LMV used in the tests was not classified as belonging to subgroups Most ...
Suzuki, Gerson Shinya 1984. "Comportamento de genótipos de alface com o alelo mo10 ao Lettuce mosaic virus e Lettuce mottle virus /." Botucatu, 2014. http://hdl.handle.net/11449/113793.
Full textBanca: Marcelo Agenor Pavan
Banca: Massaharu Marubayashi
Resumo: A alface (Lactuca sativa L.), pertencente à família Asteraceae, é uma das hortaliças mais consumidas no Brasil. Um dos principais problemas fitossanitários para essa cultura são as fitoviroses, em especial o Lettuce mosaic virus (LMV), que causa elevados prejuízos aos produtores em diversas regiões do país, além do Lettuce mottle virus (LeMoV), que vem crescendo em importância nos últimos anos. Como forma de controle, o uso de variedades resistentes é maneira mais eficaz de contornar os danos causados por vírus. Na maioria das variedades resistentes de alface faz-se o uso de genes recessivos, em sua maioria envolvidos na interação planta-vírus, são os chamados codificadores de fatores de iniciação de tradução eucarióticos (eIFs). Diante disso, este trabalho teve como objetivo avaliar dois genótipos de alface (169501 e 169501C), quanto a resistência ao LMV e ao LeMoV. Foram realizadas transmissões via extrato vegetal nos dois genótipos de alface com LMV e LeMoV em diferentes intervalos de tempo. Para LMV também foram realizadas transmissões por afídeos. As duas variedades testadas se mostraram resistentes ao LMV nas duas formas de transmissão, mas apresentaram sintomas quando inoculadas com LeMoV. Em reações de RT-PCR com oligonucleotídeos específicos, foram comprovadas a ausência de LMV e a infecção por LeMoV nas plantas inoculadas. O isolado de LMV após análise do sequenciamento da porção N' terminal da ...
Abstract: Lettuce (Lactuca sativa L.) belongs to the Asteraceae family and is one of the most consumed vegetables in Brazil. One of the major disease problems in this crop are plant viruses, especially the Lettuce mosaic virus (LMV) that cause losses to producers in various regions of the country, but also Lettuce mottle virus (LeMoV). As a form of control, the use of resistant varieties is the most effective way to overcome the damage caused by plant viruses. Most of the resistant varieties of lettuce makes the use of recessive genes, mostly involved in plant-virus interactions and characterized as eukaryotic translation initiation factor (eIFs). Thus, this study aimed to evaluate two lettuce genotypes (169501 and 169501C) for resistance to LMV and LeMoV. LMV and LeMoV were sap transmitted at different time of intervals. For LMV also transmissions with aphids were carried out. The two varieties tested were resistant to LMV in both forms of transmission, but showed symptoms when inoculated with LeMoV. In RT-PCR with specific primers, LMV was not detected but LeMoV yes, confirming the infection in the inoculated plants. The isolate of LMV used in the tests was not classified as belonging to subgroups Most ...
Mestre
George, Adrienne. "Cataloguing Diseases and Pests in Captive Corals." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3115.
Full textMatheron, Michael E. "Biology and Management of Downy Mildew of Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/579516.
Full textKerns, David L. "Common Insect Contaminants Found in Arizona Lettuce." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/144795.
Full textThis publication describes the common insects found in Arizona lettuce through the use of pictures. The insects include; lepidopterous larva, striped flea beetle, leafminer fly, leafminer mine, adult western flower thrips, winged adult aphid, false chinch bug, lygus bug, potato leafhopper, and threecornered alfalfa hopper.
Matheron, M. E., J. C. Matejka, and M. Porchas. "Field Testing of Potential New Fungicides for Control of Lettuce Diseases, 1993." College of Agriculture, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/214718.
Full textMontesclaros, Luz B. "Mapping of molecular markers surrounding the Tu gene conferring resistance to turnip mosaic virus in Lactuca sativa L." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23923.
Full textRobbins, Marjorie. "The location of Tu on the genetic map of Lactuca sativa and the identification of random amplified polymorphic DNA markers flanking and tightly linked to Tu /." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69684.
Full textBoshoff, Jane. "Biological control of Pythium wilt and root rot in hydroponically grown lettuce." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-02272007-163651/.
Full textDenman, Sandra. "Botryosphaeria diseases of proteaceae." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52721.
Full textENGLISH ABSTRACT: Fungi belonging to the genus Botryosphaeria are heterotrophic micromycetes that can be pathogens on woody plants. They cause serious, and in some cases devastating losses to crops through leaf necrosis, stem cankers and plant death. The Proteaceae cut-flower industry in South Africa accounts for 70% of the national cut-flower enterprise. Botryosphaeria diseases are a major impediment to production and trade of Proteaceae and there is an urgent need to investigate the etiology, epidemiology and control of these diseases. Losses of one of the most important proteas, P. magnifica, amount to 50% or more, locally. The main aims of this study were therefore to establish the etiology and aspects of epidemiology of Botryosphaeria stem cankers on P. magnifica and other Proteaceae, and to investigate methods of disease control. Although there is a vast body of information pertaining to this fungus, which was reviewed in Chapter 1, there is relatively little information available on Botryosphaeria on Proteaceae. The taxonomy of Botryosphaeria requires thorough review, and molecular techniques need to be employed to resolve species identities. In Chapter 2, it was found that Phyllachora proteae, a leaf pathogen of proteas, produced a Fusicoccum anamorph, which is described as F. proteae. A sphaeropsis-like synanamorph was associated with F. proteae and a new combination for P. proteae is proposed in Botryosphaeria, as B. proteae. The taxonomy of Botryosphaeria is in disarray at both the generic and the specific level. In Chapter 3 the taxonomic history of Botryosphaeria is reviewed, and the genus circumscribed and distinguished from other morphologically similar genera. Although several anamorph genera have been linked to Botryosphaeria, based on morphological observations and phylogenetic analysis of lTS rDNA sequence data, two anamorph genera are now recognised, those with pigmented conidia (Diplodia), and those with hyaline conidia (Fusicoccum). Botryosphaeria proteae should thus be excluded from Botryosphaeria. Several pathogenic Botryosphaeria spp. have an endophytic phase within their hosts. They are therefore imported unwittingly into other countries where they may pose a risk to agriculture and indigenous vegetation. The current global distribution of Botryosphaeria spp. associated with Proteaceae is clarified and a key to these taxa associated with Proteaceae is provided in Chapter 4. Five Botryosphaeria spp. are associated with cut-flower Proteaceae worldwide viz. B. lute a, B. obtusa, B. protearum, B. proteae and B. rib is. B. protearum is described as a new species. A thorough understanding of disease epidemiology is essential to effect a reduction of losses. In Chapter 5, I show that on P. magnifica, lesions caused by Botryosphaeria protearum, which lead to the formation of stem cankers, are initiated in the mid-rib vein or margin of leaves. Koch's postulates were satisfied and it was found that the number of lesions that developed from artificial inoculations correlated with starch levels present in leaves at the time of inoculation. In Chapter 6 it is shown that B. protearum exists as an endophyte in leaves of P. magnifica in naturally occurring as well as cultivated plants. In natural stands of proteas stem cankers are rare, but in cultivated plantations the incidence is high. Nutritional analyses indicate that higher levels of nitrogen occur in leaves of cultivated plants in spring, which could enhance disease development. High levels of sodium in the leaves of wild plants may restrict disease development. The severe economic losses caused by B. protearum make the search for improved methods of disease control essential. Fungicide applications form an important component of an integrated approach to disease management. In Chapter 7, in vitro tests demonstrate that tebuconazole, benomyl, prochloraz me, iprodione and fenarimol reduce the mycelial growth of B. protearum effectively. In the field there was a 25-85% reduction in the occurrence of stem cankers by applying fungicides or sanitation pruning. The best control was achieved by using benomyl, bitertanol, fenarimol, iprodione, prochloraz manganese chloride alternated with mancozeb and tebuconazole prophylactically. If sanitation pruning is combined with regular applications of fungicides, disease can be combated.
AFRIKAANSE OPSOMMING: Mikrofungi wat tot die genus Botryosphaeria behoort, is heterotrofiese organismes, wat patogenies op houtagtige plante kan wees. Hulle veroorsaak ernstige, en in sommige gevalle, verwoestende verliese, deur blaarnekrose, stamkankers en plantafsterwing. Die Proteaceae snyblom-industrie in Suid-Afrika maak 70% van die nasionale snyblomindustrie uit. Botryosphaeria siektes is 'n belangrike struikelblok in die produksie en handeldryf van Proteaceae, en daar is 'n ernstige behoefte om die etiologie, epidemiologie en beheer van siektes te ondersoek. Verliese van een van die belangrikste proteas, P. magnifica, beloop plaaslik 50% of meer. Die hoof doelstellings van hierdie studie was dus om die etiologie en epidemiologie van Botryosphaeria stamkankers op P. magnifica en ander Proteaceae vas te stel en metodes van siektebeheer te ondersoek. Hoewel daar 'n wye hoeveelheid inligting rakende die swam bestaan, wat in Hoofstuk I hersien is, is daar relatief min inligting oor Botryosphaeria op Proteaceae beskikbaar. Die taksonomie van Botryosphaeria benodig deeglike hersiening, en molekulêre tegnieke word benodig om spesie-identiteite op te klaar. In Hoofstuk 2 is gevind dat Phyllachora proteae, 'n blaarpatogeen van proteas, 'n Fusicoccum anamorf produseer, wat as F. proteae beskryf word. 'n Sphaeropsis-agtige synanamorf is met F. proteae geassosieer en 'n nuwe kombinasie vir P. proteae is as B. proteae in Botryosphaeria voorgestel. Die taksonomie van Botryosphaeria is, beide op die genus- as die spesievlak, in wanorde. In Hoofstuk 3 word die taksonomiese geskiedenis van Botryosphaeria hersien, en die genus word omskryf en van ander morfologies soortgelyke genera onderskei. Hoewel verskeie anamorf genera al met Botryosphaeria op grond van morfologiese waarnemings en filogenetiese analise van ITS rDNA volgorde data verbind is, word twee anamorf genera nou herken, dié met gepigmenteerde konidia (Diplodia), en dié met deurskynende konidia (Fusicoccum). Botryosphaeria proteae moet dus van Botryosphaeria uitgesluit word. Verskeie patogeniese Botryosphaeria spp. het 'n endofitiese fase in hul lewenssiklus. Hulle word dus onwetend in ander lande ingevoer waar hulle 'n gevaar vir landbou en inheemse plantegroei kan inhou. Die huidige wêreldverspreiding van Botryosphaeria spp. wat met Proteaceae geassosieer word is opgeklaar, en in Hoofstuk 4 word 'n sleutel tot die taksa wat met Proteaceae geassosieer word verskaf. Vyf Botryosphaeria spp. word met snyblom Proteaceae wêreldwyd geassosieer, naamlik B. lutea, B. protearum, B. proteae, B. ribis en B. obtusa. B. protearum word as 'n nuwe spesie beskryf. 'n Deeglike kennis van siekte-epidemiologie is noodsaaklik ten einde verliese te verminder. In Hoofstuk 5 dui ek aan dat letsels wat lei tot stamkankers, veroorsaak deur Botryosphaeria protearum op P. magnifica, in die hoofnerf of rant van blare ontstaan. Koch se postulate is uitgevoer en daar is vasgestel dat die aantal letsels wat vanuit kunsmatige inokulasies ontwikkel het korreleer met die styselvlakke teenwoordig in die blare ten tye van die inokulasie. In Hoofstuk 6 word getoon dat B. protearum as 'n endofiet in die blare van P. magnifica. In natuurlike standplase van proteas is stamkankers skaars, maar in verboude plantasies is die voorkoms hoog. Voedingsanalises dui aan dat hoër vlakke van stikstof in die blare van verboude plante in die lente voorkom, wat siekte-ontwikkeling moontlik kan bevorder. Hoë vlakke van natrium in die blare van natuurlike plante mag siekteontwikkeling beperk. Die ernstige ekonomiese verliese wat deur B. protearum veroorsaak word, maak die soektog na verbeterde metodes van siektebeheer noodsaaklik. Fungisiedtoedienings maak 'n belangrike deel uit van 'n geïntegreerde benadering tot siektebeheer. In Hoofstuk 7 dui in vitro toetse aan dat tebuconazole, benomyl, prochloraz me, iprodione en fenarimol die miseliumgroei van B. protearum effektief verminder. 'n Vermindering van 25-85% is aangetoon in die voorkoms van stamkankers in die veld, deur die toediening van fungisiedes en sanitasiesnoei. Die beste beheer is verkry deur die voorkomende toediening van benomyl, bitertanol, fenarimol, iprodione en prochloraz manganese chloride, afgewissel met mancozeb en tebuconazole, op plante in die veld. Indien sanitasiesnoei met gereelde toedienings van fungisiedes gekombineer word, kan die siekte bekamp word.
Lubbe, Carolien M. "Colletotrichum diseases of Proteaceae." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/53732.
Full textENGLISH ABSTRACT: This thesis consists of four chapters that present research findings on Colletotrichum diseases associated with Proteaceae worldwide. The first chapter is a review of literature regarding the taxonomy and histology of Colletotrichum species associated with Proteaceae. The literature is not restricted to Proteaceae hosts, as information regarding Colletotrichum on Proteaceae is very limited. In chapter two, Colletotrichum spp. associated with proteaceous hosts growing in various parts of the world were identified based on morphology, sequence data of the internal transcribed spacer region (ITS-I, ITS-2), the 5.8S gene, and partial sequences of the B-tubulin gene. Four species of Colletotrichum were associated with Proteaceae. Colletotrichum gloeosporioides was isolated from Protea cynaroides cultivated in South Africa and Zimbabwe and from a Leucospermum sp. in Portugal, but is known to occur worldwide on numerous hosts. A recently described species, C. boninense, was associated with Zimbabwean and Australian Proteaceae, but also occurred on a Eucalyptus sp. in South Africa. This represents a major geographical and host extension for the species, and a description of the African strains is provided. Colletotrichum crassipes was represented by a single isolate obtained from a Dryandra plant in Madeira. Colletotrichum acutatum was isolated from Protea and Leucadendron in South Africa as well as from other proteaceous hosts occurring elsewhere. Colletotrichum acutatum f. sp. hakea was isolated from Hakea in South Africa. In chapter three, pathogenicity of these Colletotrichum species to certain proteas was established, relative aggressiveness of the different species tested and host response to them were compared as well as the effect that wounding had on host response. From the results obtained it is concluded that C. acutatum and C. gloeosporioides are the primary pathogens associated with Colletotrichum leaf necrosis, and C. acutatum is the main cause of anthracnose and stem necrosis of Proteaceae in South Africa. A histological study was performed in chapter four in response to the findings from the previous chapter. The behaviour of two C. acutatum isolates (one originating from Protea and the other from Hakea, C. acuataum f.sp. hakea) was studied on inoculated Protea leaf surfaces using light and scanning electron microscopy. Colletotrichum acutatum from Protea formed melanised appressoria on the leaf surface, whereas C. acutatum from Hakea formed very low numbers of both melanised and unmelanised appressoria. Most of the appressoria formed by C. acutatum from Protea were formed on the cell junctions and on the periclinal walls of the epidermal cells. From this study it is clear that C. acutatum f. sp. hakea is not a pathogen of Protea. Consequently the current use of this isolate as a biological control agent of Hakea in South Africa poses no threat to indigenous Protea species. Colletotrichum acutatum from Protea (although closely related to C. acutatum f. sp. hakea), is a pathogen of Protea, which was confirmed by histological observations. In conclusion, the present study has shown that several species of Colletotrichum are associated with diseased Proteaceae. These species differed in their pathogenicity and aggressiveness when inoculated onto certain protea cultivars. These differences could be partially explained by examining the behaviour of C. acutatum on the leaf surface. It is clear, however, that the distribution of the different species, their aggressrveness on different Proteaceae and their modes of infection needs to be investigated further. This work provides a basis for future research on the long-term effective management of these pathogens in fynbos production.
AFRIKAANSE OPSOMMING: Hierdie tesis bestaan uit vier hoofstukke wat handeloor navorsing van Colletotrichum siektes van Proteaceae wêreldwyd. Die eerste hoofstuk is 'n oorsig van literatuur rakende die taksonomie en histologie van die Colletotrichum spesies wat met Proteaceae geassosieer word. Die literatuur oorsig is nie beperk tot die Proteaceae nie aangesien baie min inligting rakende Colletotrichum op Proteaceae bestaan. In die tweede hoofstuk word die Colletotrichum spesies wat met proteas in verskeie dele van die wêreld geassosieer word, op grond van morfologie, DNS volgorde data van die interne getranskribeerde spasieerder area ("ITS-I, ITS-2"), die 5.8S geen, en gedeeltelike DNS volgordes van die B-tubulin geen geïdentifiseer. Vier Colletotrichum spesies is met die Proteaceae geassosieer. Colletotrichum gloeosporioides is geïsoleer vanaf Protea cynaroides wat in Suid-Afrika en Zimbabwe gekweek is en vanaf 'n Leucospermum sp. in Portugal, maar is bekend op verskeie gashere wêreldwyd. 'n Spesie wat onlangs beskryf is, C. boninense, is met Zimbabwiese en Australiaanse Proteaceae geassosieer, maar kom ook op 'n Eucalyptus sp. in Suid-Afrika voor. Dit is 'n groot uitbreiding van die geografiese voorkoms en gasheerreeks van hierdie spesie en 'n beskrywing van die Afrikaanse rasse word gegee. Colletotrichum crassipes is verteenwoordig deur 'n enkele isolaat wat vanaf 'n Dryandra plant in Madeira verkry is. Colletotrichum acutatum is vanaf Protea en Leucadendron in Suid-Afrika asook vanaf ander proteas wat elders voorkom, geïsoleer. Colletotrichum acutatum f. sp. hakea is vanaf Hakea in Suid-Afrika geïsoleer. In hoofstuk drie is die patogenisiteit van hierdie Colletotrichum spesies teenoor sekere proteas getoets, die relatiewe aggressiwiteit van die verskillende spesies is vergelyk, asook die gasheer se reaksie teenoor die spesies en die effek wat verwonding op die gasheer gehad het. Daar kan afgelei word vanaf die resultate dat C. acutatum en C. gloeosporioides die primêre patogene is wat met Colletotrichum blaarnekrose geassosieer word, en dat C. acutatum die hoof oorsaak is van antraknose en lootnekrose van Proteaceae in Suid-Afrika. 'n Histologiese studie is in hoofstuk vier uitgevoer in reaksie op die bevindings van die vorige hoofstuk. Die gedrag van twee C. acutatum isolate (een vanaf Protea en die ander vanaf Hakea, C. acutatum f.sp. hakea) op die oppervlaktes van geïnokuleerde Protea blare is bestudeer deur gebruik te maak van lig- en skandeer-elektronmikroskopie. Colletotrichum acutatum vanaf Protea vorm gemelaniseerde appressoria op die blaaroppervlak, terwyl C. acutatum vanaf Hakea klein hoeveelhede van beide gemelaniseerde en ongemelaniseerde appressoria vorm. Meeste van die appressoria wat deur C. acutatum vanaf Protea gevorm word, vorm op die aanhegtingspunte tussen selle en op die periklinale wande van die epidermale selle. Vanuit hierdie studie is dit duidelik dat C. acutatum f. sp. hakea nie 'n patogeen van Protea is nie. Gevolglik hou die huidige gebruik van hierdie isolaat as biologiese beheer agent van Hakea in Suid-Afrika geen gevaar in vir inheemse Protea spesies nie. Colletotrichum acutatum vanaf Protea (alhoewel dit naverwant is aan C. acutatum f. sp. hakea) is 'n patogeen van Protea en hierdie stelling is ook bevestig deur histologiese waarnemmgs. Ter samevatting het hierdie studie getoon dat verskeie Colletotrichum spesies geassosieer word met siektes van Proteaceae. Hierdie spesies het van mekaar verskil rakende patogenisiteit en aggressiwiteit nadat hulle op sekere protea kultivars geïnokuleer is. Hierdie verskille kon gedeeltelik verklaar word deur die gedrag van C. acutatum op die blaaroppervlaktes van verskillende protea kultivars. Dit is duidelik dat die verspreiding van die verskillende spesies, hulle aggressiwiteit op verskillende Proteaceae en hul infeksie metodes verder ondersoek moet word. Hierdie studie verskaf 'n basis vir toekomstige navorsing rakende lang-termyn effektiewe bestuur van hierdie patogene in fynbos aanplantings.
Matheron, M., J. McGrady, M. Butler, M. Rethwisch, J. Matejka, and P. Tilt. "Effect of Sunstainable Versus Conventional Fertilization Practices on Populations of Pythium and Fusarium on Roots of Lettuce in 1990 Field Test." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221453.
Full textMatheron, M. E., and J. C. Matejka. "Sclerotinia Leaf Drop of Lettuce - Screening New Fungicides for Disease Control in 1986." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/221404.
Full textMcGrady, John, Vince Rubatzky, Norm Oebker, Tim Hartz, Marvin Butler, Phil Tilt, and Sherry Hagerman. "Cultural Alternative for Avoidance of Lettuce Infectious Yellows Virus (LIYV)." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221452.
Full textMatheron, M. E., and J. C. Matejka. "Effect of Fungicides Applied at Different Rates on Control of Sclerotinia Leaf Drop of Lettuce -- 1990 Field Test." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221455.
Full textMatheron, Michael E., and Martin Porchas. "Downy and Powdery Mildew of Lettuce: Comparison of Chemical Management Tools in 1997." College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/221600.
Full textWilcox, Mark, and Michael Matheron. "Field Evaluation of Head Lettuce Cultivars for Susceptibility to Sclerotinia Leaf Drop in 1997." College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/221601.
Full textMatheron, Michael E., and Martin Porchas. "Field Evaluation of Potential New Fungicides for Control of Lettuce Downey and Powdery Mildew in 1994 and 1995." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/221462.
Full textMatheron, Michael E., Iraj J. Misaghi, Martin Porchas, and Dominic DeCianne. "Field Evaluation of Potential New Fungicides for Control of Sclerotinia Leaf Drop of Lettuce in 1994 and 1995." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/221473.
Full textMatheron, Michael E., and Martin Porchas. "Evaluation of New Fungicides for Management of Downy and Powdery Mildew of Lettuce in 1998." College of Agriculture, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/221659.
Full textMatheron, Michael E., and Martin Porchas. "New Fungicides Evaluated for Control of Sclerotinia Leaf Drop of Lettuce in 1997 and 1998." College of Agriculture, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/221661.
Full textKalonji, Kabengele Muzela J. B. "Evaluation of three fungicides for control of soilborne diseases of lettuce seedlings." Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/29549.
Full textDissertation (MInstAgrar)--University of Pretoria, 2008.
Microbiology and Plant Pathology
unrestricted
Noronha, Christine M. (Christine Mary). "Effects of density and host plant type on fecundity and survival of Delia radicum (Bouché), D. Antiqua (Meigen) and D. Platura (Meigen) (Diptera: Anthomyiidae)." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41017.
Full textAn optimum density for maximum fecundity per female was observed when the four experimental densities were compared. This optimum density was higher on host than on non-host plants. CM females were host specific and did not oviposit on non-host plants. Rates of oviposition and mortality over a 30-day period were calculated for each density. The rate of oviposition was slower at higher densities on host plants for CM, OM and SCM. The rate of mortality increased at the highest density for CM (cabbage), OM (bean) and SCM (cabbage), but remained unaffected for OM on onion and cabbage and for SCM on onion and bean, when densities were compared. For OM, a delay in the rate of oviposition and mortality on cabbage (non-host plant) when compared with onion (host plant), suggests that cabbage was not as readily accepted as an oviposition site. Interspecific competition experiments at six density ratio's of SCM:OM indicated increased fecundity, or an increase in the rate of oviposition for OM, at the lower densities when single and mixed species were compared. For SCM no effects on fecundity were recorded, but the rate of oviposition was slower and rate of mortality faster at the lowest density in the presence of OM. Similar studies with SCM and CM showed no such effects of competition.
Host plant exposure of SCM females during the pre-oviposition period resulted in a delay in initial acceptance of subsequent host plants as oviposition sites. This happened only when females were exposed to a secondary host during the pre-oviposition period. Once oviposition began, host discrimination ceased and a switch in oviposition sites to the preferred host did not alter the rate of oviposition. In CM, the rate of larval development increased at density 6 (optimum density). Above this density a decrease in the rate of development and a significant reduction in pupal weight was observed. Time required for fly emergence was not affected by increasing larval densities.
Wakgari, Waktola (Waktola Muleta). "Biology, ecology and management of white wax scale, Ceroplastes destructor Newstead (Hemiptera: Coccidae), on citrus and syzygium." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51637.
Full textENGLISH ABSTRACT: The population density of the white wax scale, Ceroplastes destructor Newstead, has increased since 1994 in certain areas of Western and parts of Eastern Cape Provinces of South Africa where citrus is grown, particularly on Citrus reticulata (Blanco). A study was conducted to investigate its morphology, biology and ecology as contributions to the development of a sound integrated management programme. Characteristics of the immature stages and adult females were described and illustrated from field-collected and slide-mounted specimens. A key to the different stages and morphometeric characteristics useful for separating them are provided. No significant differences in female fecundity were found between orchards (P > 0.05). However, fecundity varied significantly between female size classes from the same orchard (P < 0.001). Female body-size also differed significantly between orchards (P < 0.05) and was significantly positively correlated with fecundity (P < 0.01). C. destructor has one discrete generation per year in South Africa. Oviposition commenced in November and continued through to the end of December with a few females ovipositing until mid January. Population density of the second instar peaked in February while the third instar extended from March to the end of July, followed by a peak population of adults in August. Seven primary and three secondary parasitoids, as well as four predator species attacking C. destructor were identified. Aprostocetus (= Tetrastichus) ceroplastae (Girault) was the dominant species, accounting for 78.87% of the total primary parasitoids reared. Peak numbers of parasitoids and predators were synchronized with peak emergence of susceptible scale stages, indicating that the host-parasitoid/predator system contained a density-dependent regulatory mechanism. Key mortality factors varied slightly between two of the orchards. Key stage mortality determined from a cohort life table was generally in the third instar (LIlI) and preovipositional female (POF) stage. Significant density-dependent mortality factors were demonstrated for the first instar (LI) and PDF stage. Dispersal of C. destructor is by first instar nymphs and the numbers caught on a series of yellow sticky traps varied significantly between crawler densities at the source, trap distances and trap directions from the source (P < 0.001). The numbers caught were positively correlated to the initial crawler density at the source (P < 0.01), suggesting that dispersal was density dependent. Trap distance and the numbers caught were inversely correlated (P < 0.01). Evaluation of effects of different densities of C. destructor on growth, survivorship and reproduction of scales as well as on leaf bearing ability of trees and area of leaf surface covered with sooty mould fungus was carried out on naturally infested Syzygium (= Eugenia) malaccensis (L.) plants. Scale body size and fecundity were inversely related to scale density (P < 0.01), suggesting density-dependent intraspecific competition. Scale survivorship generally declined with increasing density whereas scale parasitism and predation were positively correlated with density (P < 0.05). At high scale densities production of new leaves was significantly reduced (P < 0.01), reducing the resource base for subsequent generations of scale. Scale density and leaf area covered with sooty mould fungus were significantly positively correlated (P < 0.05). The toxicity of four synthetic insecticides against the three immature stages of C. destructor and of eight insecticides against the parasitoid A. ceroplastae was evaluated. Development of the first and second instars of C. destructor was completely arrested by the chemicals. Female fecundity, fertility and body sizes of survivors of treatments applied at the LIII stage were not significantly affected by any of the chemicals (P > 0.05). All the chemicals exhibited high toxicity to A. ceroplastae and hence are not recommended for integrated management of C. destructor in citrus orchards where A. ceroplastae plays an important role.
AFRIKAANSE OPSOMMING: Die populasiedigtheid van die witwasdopluis, Ceroplastes destructor Newstead, het sedert 1994 toegeneem in sekere gebiede van die Weskaap en Ooskaap provinsies van Suid-Afrika waar sitrus verbou word, veralop Citrus reticulata (Blanco). 'n Studie van hierdie insek se morfologie, biologie en ekologie is onderneem as bydrae tot die ontwikkeling van 'n geïntegreerde bestuursprogram. Die karaktertrekke van die onvolwasse stadia en die volwasse wyfies is beskryf en geïllustreer vanaf eksemplare wat in die veld versamel is en op g1asplaatjies gemonteer is. 'n Sleutel vir die verskillende stadia en morfometriese kenmerke wat nuttig is om hulle te onderskei, word voorsien. Geen beduidende verskille in die vrugbaarheid van wyfies van verskillende boorde is gevind nie (P < 0.05). Vrugbaarheid het egter betekenisvol verskil by die verskillende grootteklasse van wyfies uit dieselfde boord (P < 0.001). Die liggaamsgrootte van wyfies uit verskillende boorde het betekenisvol verskil (P < 0.05) en was betekenisvol positief gekorreleer met vrugbaarheid (P < 0.01). C. destructor het een generasie per jaar in Suid-Afrika. Eierlegging het in November begin en aangehou tot aan die einde van Desember, met enkele wyfies wat nog tot in middel Januarie eiers gelê het. Die populasiedigtheid van die tweede instar het 'n hoogtepunt in Februarie bereik, terwyl die derde instar van Maart tot aan die einde van Julie geduur het, gevolg deur 'n piekbevolking van volwassenes in Augustus. Sewe primêre en drie sekondêre parasitoïde asook vier predator spesies wat C destructor aanval, is geïdentifiseer. Aprostocetus (=Tetrastichus) ceroplastae (Girault) was die dominante spesies wat 78.87% van die totale aantal primêre parasitoïde wat uitgeteel is, uitgemaak het. Die pieke in die getalle van parasitoïde en predatore was gesinchroniseer met pieke in die verskyning van die gevoelige stadia, wat dui op die aanwesigheid van 'n digtheidsafhanklike regulatoriese meganisme. Die sleutel mortaliteitsfaktore het effens gevarieer tussen twee van die boorde. Die sleutelstadium van mortaliteit, soos bepaal m.b.v. 'n kohort lewenstabel, was gewoonlik die derde instar (LIlI) en die preoviposisionele wyfie (POW). Betekenisvolle digtheidsafhanklike mortaliteitsfaktore IS aangetoon vir die eerste instar (LI) en die POW. Die verspreiding van C.destructor vind plaas deur die eerste instar nimfe en die getalle wat op 'n reeks van taai geel valle gevang is, het betekenisvol gewissel volgens kruiperdigthede by die bron, asook die afstand en rigting van die valle vanaf die bron (P < 0.001). Die getalle wat gevang is, was positief gekorreleer met die aanvanklike kruiperdigtheid by die bron (P < 0.01), wat daarop dui dat verspreiding digtheidsafhanklik was. Die afstand van die valle en die aantal wat gevang is, was omgekeerd gekorreleer (P < 0.01). 'n Evaluering van die invloed van verskillende digthede van C. destructor op die groei, oorlewing en reproduksie van dopluise, asook die vermoë van bome om blare te dra en die area van die blaaroppervlak wat met roetskimmel besmet is, is uitgevoer op plante van Syzygium (= Eugenia) malaccensis (L.) met 'n natuurlike besmetting. Die liggaamsgrootte en vrugbaarheid van die dopluise was omgekeerd gekorreleer met hulle digtheid (P < 0.01), wat dui op digtheidsafhanklike intraspesifieke kompetisie. Die oorlewing van die dopluise het oor die algemeen afgeneem met toenemende digtheid, terwyl parasitisme en predasie positief gekorreleer was met digtheid (P < 0.05). By hoë dopluisdigthede het die produksie van nuwe blare betekenisvol afgeneem (P < 0.01), wat die hulpbronbasis vir daaropvolgende generasies van dopluise verswak. Die dopluisdigtheid en blaaroppervlak wat met roetskimmel bedek was, was positief gekorreleer (P < 0.05). Die toksisiteit van vier sintetiese insektemiddels teenoor die drie onvolwasse stadia van C. destructor en van agt insektemiddels teenoor die parasitoïd A. ceroplastae is geëvalueer. Die ontwikkeling van die eerste en tweede instars van C. destructor is heeltemal stopgesit deur die middels. Die fekunditeit, fertiliteit en liggaamsgrootte van wyfies wat toedienings op die LIIl stadium oorleef het, is nie betekenisvol ge-affekteer deur enige van die middels nie (P < 0.05). Al die middels was baie toksies teenoor A. ceroplastae en word dus nie aanbeveel vir die geïntegreerde bestuur van C. destructor waar A. ceroplastae 'n belangrike rol speel nie.
Rodriguez, Juan Jose. "Movement and Accumulation of Candidatus Liberibacter Solanacearum in Potato Plants." Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26726.
Full textNorth Dakota State University. Department of Plant Pathology
Matheson, Michael E., and Joseph C. Matejka. "Sclerotinia Leaf Drop on Lettuce -- Evaluation of New Fungicides for Disease Control." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/214265.
Full textPier, J. W., T. A. Doerge, and T. McCreary. "Fungicides Evaluated for Control of Sclerotinia Leaf Drop of Lettuce in 1991 Field Test." College of Agriculture, University of Arizona (Tucson, AZ), 1992. http://hdl.handle.net/10150/214510.
Full textMatheron, Michael E., and Martin Porchas. "Management of Sclerotinia Leaf Drop on Lettuce: Efficacy of Fungicides in 1996 Field Trial." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/214737.
Full textMatheron, Michael E., and Martin Porchas. "Management of Downy and Powdery Mildew on Lettuce: Efficacy of Fungicides in 1996 Field Trial." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/214738.
Full textNelson, Merritt R., Joseph C. Matejka, and Judith K. Brown. "Use of Stylet Oil to Slow the Spread of Lettuce Infectious Yellows Virus." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/214262.
Full textMatheron, M. E., and J. C. Matejka. "Sclerotinia Leaf Drop of Lettuce - Testing New Fungicides and Formulations of Ronilan for Disease Control." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/214477.
Full textMatheron, M. E., R. Leonard, and G. Major. "Fungicides Evaluated for Control of Rhizoctonia Bottom Rot of Lettuce in 1991 Field Trials." College of Agriculture, University of Arizona (Tucson, AZ), 1992. http://hdl.handle.net/10150/214512.
Full textJensen, Paul. "An evaluation of potential apple replant disease treatments for Quebec /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63295.
Full text