Dissertation (PhD (Agric))--University of Stellenbosch, 2002. / ENGLISH 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.

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[Typewritten] Includes bibliography.

There is currently little knowledge about the dynamics of invertebrates in Australian viticultural ecosystems. This study was conducted in Coonawarra vineyards over three seasons (years) and has focused on identifying natural enemies, their seasonal phenology, multiple species interactions, and potential for the suppression of the pest lepidopteran Epiphyas postvittana (Tortricidae). The work presented in this thesis shows that endemic natural enemies have far greater potential to control E. postvittana than has been realised. An initial survey identified a diverse and abundant range of potential natural enemies. Of these, the species most likely to attack E. postvittana include a predatory mite Anystis baccarum and a number of hymenopteran parasitoids. The most abundant parasitoid in the vineyards was a braconid, Dolichogenidea tasmanica. Understanding the characteristic behaviour of parasitoids in response to host density can help to gauge their potential for pest suppression. The results of large-scale field experiments showed that the response of D. tasmanica to the density of E. postvittana was inversely density-dependent, and that parasitism was consistently higher in Cabernet Sauvignon compared with Chardonnay varieties. Despite the fact that interactions among multiple species of natural enemies can increase or decrease pest suppression, particularly when they share a common prey/host, few multispecies interactions have been investigated. Laboratory studies identified a novel interaction between the predatory mite A. baccarum an abundant predator in the vine canopy, the parasitoid D. tasmanica and host E. postvittana larvae. Although A. baccarum readily ate E. postvittana eggs and free roaming larvae, they could not access larva in their silk leaf rolls. However, the addition of D. tasmanica significantly increased predation of E. postvittana larvae, by altering the behaviour of host larvae and increasing their vulnerability to the mite. Experiments conducted at a landscape level in the Coonawarra showed that D. tasmanica was also present in habitat other than vineyards including native vegetation. However, it was not present in highly disturbed habitats. Although the exact mechanism for this remains unknown, results indicate that viticultural practices and resources in the surrounding landscape can influence the presence of parasitoids. Together, the findings presented in this thesis make a significant contribution towards developing sustainable pest management in Australian viticulture. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320930 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

There is currently little knowledge about the dynamics of invertebrates in Australian viticultural ecosystems. This study was conducted in Coonawarra vineyards over three seasons (years) and has focused on identifying natural enemies, their seasonal phenology, multiple species interactions, and potential for the suppression of the pest lepidopteran Epiphyas postvittana (Tortricidae). The work presented in this thesis shows that endemic natural enemies have far greater potential to control E. postvittana than has been realised. An initial survey identified a diverse and abundant range of potential natural enemies. Of these, the species most likely to attack E. postvittana include a predatory mite Anystis baccarum and a number of hymenopteran parasitoids. The most abundant parasitoid in the vineyards was a braconid, Dolichogenidea tasmanica. Understanding the characteristic behaviour of parasitoids in response to host density can help to gauge their potential for pest suppression. The results of large-scale field experiments showed that the response of D. tasmanica to the density of E. postvittana was inversely density-dependent, and that parasitism was consistently higher in Cabernet Sauvignon compared with Chardonnay varieties. Despite the fact that interactions among multiple species of natural enemies can increase or decrease pest suppression, particularly when they share a common prey/host, few multispecies interactions have been investigated. Laboratory studies identified a novel interaction between the predatory mite A. baccarum an abundant predator in the vine canopy, the parasitoid D. tasmanica and host E. postvittana larvae. Although A. baccarum readily ate E. postvittana eggs and free roaming larvae, they could not access larva in their silk leaf rolls. However, the addition of D. tasmanica significantly increased predation of E. postvittana larvae, by altering the behaviour of host larvae and increasing their vulnerability to the mite. Experiments conducted at a landscape level in the Coonawarra showed that D. tasmanica was also present in habitat other than vineyards including native vegetation. However, it was not present in highly disturbed habitats. Although the exact mechanism for this remains unknown, results indicate that viticultural practices and resources in the surrounding landscape can influence the presence of parasitoids. Together, the findings presented in this thesis make a significant contribution towards developing sustainable pest management in Australian viticulture. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320930 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Graduation date: 2004

The efficiencies of wet sieving/sucrose centrifugation (WS/SC) recovery of Pratylenchus penetrans (59 %), Paratylenchus sp., (80 %), and Criconemella xenoplax (66 %) were established. Baermann funnels (BF) recovered significantly more P. penetrans (p = 0.01) and significantly less (p = 0.01) C. xenoplax than did WS/SC. While densities of P. penetrans in stored soil remained constant over the three days following field sample collection, Paratylenchus sp. and C. xenoplax densities increased significantly on the second day and decreased to their original level on the third day. During mist chamber extraction, P. penetrans continued to emerge from peppermint root tissue for 38 days, but 90 % of the total was recovered after 10 days. The standard core, consisting of 500 g dry soil plus the roots and rhizomes in that soil, was developed to express endoparasitic and ectoparasitic nematode densities in peppermint field soil, roots, and rhizomes. Enumerating nematode densities within the different plantsoil components of a particular volume of soil more closely describes the total nematode population pressure on the plant growing in that volume of soil. Therefore, endoparasitic nematode population levels were expressed as numbers in standard core soil, roots, rhizomes, or total core (soil, root, and rhizome populations combined). P. penetrans populations in peppermint fields peaked in early May, decreased through the summer, peaked again in August, and decreased through the fall to a low winter level. Peaks in the P. penetrans population followed peppermint root weight peaks by 3 to 6 wks. Paratylenchus sp. populations remained at relatively low levels throughout the year except for a pronounced peak in August, which followed the root weight peak by 3 to 6 wks. The C. xenoplax population also peaked 3 to 6 wks after the August root weight peak but fluctuated markedly throughout the remainder of the year. From 70 to 90 % of the total P. penetrans population was in roots in early May, decreased to 40 to 50 % by late June and 20 to 40 % in August. Up to 20 % of the population was in rhizomes on some dates, but the rhizome percentage was usually less than 10. Fewer P. penetrans were recovered from rhizomes during the harsh winter of 1988-89 than during the mild winter of 1989-90. Analysis of point samples (pretreatment, posttreatment, and harvest samples) and area under nematode population curves (AUNPC) were used to compare nematode populations in oxamyl-treated (1.1 kg a.i./ha) and nontreated plots in two peppermint fields through the two growing seasons. Point sample analyses detected significant decreases in treated soil, root, and total standard core P. benetrans populations compared to nontreated populations in several pretreatment and harvest sample dates and in two rhizome harvest sample dates. No treatment differences were observed in Paratylenchus sp. or C. xenoplax populations using this analysis. AUNPC analysis detected significant decreases in several treated root and rhizome P. penetrans populations compared to nontreated populations and in total core populations in field 1 during one growing season and in field 2 during two growing seasons. Significant decreases in C. xenoplax populations were observed in one field during one growing season. Peppermint hay weight was significantly greater in treated than in nontreated plots in one of three fields in 1988 and in one of three fields during 1989. Oil in ml/kg fresh hay weight was significantly lower in treated than in nontreated plots in one of three fields during 1989. No treatment differences were detected in milliliters of oil distilled from 2m² field area. Peppermint oil production is the final measure of a treatment from a mint grower's perspective. Because oxamyl had no effect on mint oil production, AUNPC appears to be a better measure of parasitic nematode pressure on peppermint, since this method of analysis detected fewer significant differences between nematode populations between treated and non-treated plots. / Graduation date: 1991

The effects of fenamiphos on soil and root populations of Pratylenchus penetrans were evaluated in four red raspberry cv. Willamette fields in Northwestern Oregon. Field 1 was a silty clay loam with 53% organic matter (OM). Field 2 and 3 were silty loam soils with 3.25 and 2.55% OM, respectively and field 4 was a silty clay with 7.1% OM. The nematicide, fenamiphos (10 kg a.i./ha) was applied in broadcast or band treatments on November 15, 1989. Additional plots in field 3, received a band-nematicide treatment on December 28, 1989 to evaluate the effect of application date on the control of P. penetrans in red raspberry. Field 4 had plots in sites with and without grass and weed ground cover in the aisles between raspberry rows to examine effects of ground cover on nematicide efficacy. Nematodes from soil and roots were sampled monthly from all plots in each field from October 1989 to October 1990. Soil populations of P. penetrans sampled within rows decreased between the October and December sampling dates in all four fields. Soil populations in 3 fields increased in density during mid-summer and reached their highest peak in the middle of September. A similar pattern occurred in P. penetrans soil populations from plots with or without ground cover in aisles between rows of raspberry in field 4. However, in this field, numbers increased in July and reached their peak density in August. Root populations of P. penetrans from red raspberry reached their highest number during spring and summer at all fields. No significant (P>0.05) differences in effectiveness of fenamiphos were detected between band and broadcast method of application and, also between the 2 application dates. Seasonal mean densities of soil populations from band application was only significantly lower than in nontreated controls in areas with ground cover in field 4, respectively. High variability in the numbers of P. penetrans in soil and roots of raspberry was observed throughout the year. Therefore, conclusions about the effectiveness of fenamiphos were difficult to assess. The efficiency of Baermann funnels was 43.9%, when a known number of P. penetrans was added to soil. Total yields of P. penetrans extracted from raspberry roots by mist chamber root extraction (MCRE) were higher (P = 0.05) than yields extracted by polyethylene plastic bag root incubation (PBRI). Approximately 90% of the total P. penetrans recovered was achieved after three and seven days of extraction for PBRI and MCRE, respectively. However, the extraction efficiency of MCRE was 30% higher than PBRI and the daily recovery lasted 28 and 18 days, respectively. / Graduation date: 1992

Computer decision aids can help integrate and apply diverse sources of information and expertise to problems of integrated pest management (IPM) in agriculture and forestry. AppleMgr combines a rule-based expert system with databases and spreadsheets in a prototype decision aid intended to be expanded and modified for use by extension workers in the Northwest U.S. The program requires an IBMcompatible microcomputer with hard disk. AppleMgr concentrates on the two most important insect pests on apple in the Northwest--codling moth, Cydia, pomonella (L.), and San Jose scale, Quadraspidiotus perniciosus Comstock, and on phytophagous mites, whose control largely depends on predators. The primary goal of AppleMgr is to demonstrate an improved process of decision making in apple IPM. AppleMgr is composed of modules for diagnosis of pest injury, identification of pest and natural enemy specimens, and management. The first two modules arrive at conclusions through backward-chaining inference from user observations. The management module uses backward chaining supplemented with external calculation programs to find the net benefit of a pesticide application. A method is included to predict yield and fruit size from crop samples. Cullage from codling moth and San Jose scale, mite effect on fruit size, probability of biological mite control and pesticide efficacy are predicted from researchers' data and estimates. Selected relative beneficial and adverse side effects of pesticides are presented in spreadsheets. An analysis of packing house records for apple crops from eight orchards at three yields using 1987 and 1988 prices and packing charges showed that net crop value varied by up to $8000 per acre. The variability in crop value and the importance of adverse side effects of pesticides suggest that the commonly-used "action thresholds" for treatment are seriously inadequate. AppleMgr may point the way toward more dynamic and realistic methods of IPM decision making. / Graduation date: 1990

No description available.