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Optimization of a waste polyethylene terephthalate/fly ash hybrid concrete composite in slabsNkomo, Nkosilathi Zinti 08 1900 (has links)
D. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Cracked concrete slabs are a problem due to several factors such as poor maintenance, insufficient reinforcement or steel corrosion leading to crack propagation. There is a need to increase the load-bearing capacity of concrete slabs and increase their life span. The use of waste Polyethylene Terephthalate (PET) fibres and fly ash in a hybrid composite slab dramatically alleviates the problem of crack propagation and failure sustainably. This study aimed to optimize a waste PET fibre/fly ash hybrid cement composite for use in slabs. This study characterized the raw materials used, including fly ash and aggregates. After that, concrete test specimens were fabricated using the PET fibres and fly ash following the full factorial experimental design. The developed specimens were then tested to ascertain their material strength properties. Model development was carried out using Minitab Software Version 14, and subsequent experimental validation was carried out. After that, the PET and fly ash optimisation for maximum favourable response outcome was carried out.
The fly ash was found to belong to the Class F category with particle size ranging from 0.31 μm to 800 μm. The fly ash was mainly spherical and consisted of Ca, Al, P, Si, and trace amounts of Ti and Mg. The spherical shape of the fly ash helped improve the concrete's workability. The river sand had a fineness modulus of 3.69, considered coarse sand. The fine aggregate showed uniform particle size distribution with a uniformity coefficient of 4.007. The coarse aggregate characterisation was carried out and revealed that the aggregate particle size was 13 mm in size. The coarse aggregate had a uniformity coefficient of 4.007, which implied the aggregate was well graded. The coarse aggregate had a high flakiness index of 74.82 % and an acceptable elongation index of 46.72 %.
Full factorial methodology experimental design was employed to fabricate the test specimens by simultaneously varying the independent factors to develop a model for overall response variation. The slump value was observed to increase with the addition of fly ash. However, the addition of PET fibre decreased the slump value with incremental amounts of fibre. The combined effect of fibre addition and fly ash showed a general decreasing slump value for all quantities of fly ash content. The compressive strength of PET fibre only composite had maximum strength at 0.5% fibre addition, and the composite with fly ash alone had the maximum compressive strength at 15%. The combined optimum compressive strength for fibre and fly ash was at 0.5 % and 15 %, respectively, with a 15.54 N/mm2. The split tensile strength decreased with an increase in fibre content. However, the fibre provided crack retardation. Fly ash increased the split tensile strength significantly to a peak of 2.35 N/mm2 for 20 % fly ash addition. The combined addition of fibre and fly ash had an optimum split tensile strength of 2.79 N/mm2 at 0.5 % fibre and 20 % fly ash. The addition of fibre had an optimum split tensile strength at 0.5% of 1.82 N/mm2. The fly ash increased the flexural strength, with optimum strength at 15 %. The combined addition of fibre and fly ash created optimum flexural strength at 0.5% and 30 %, respectively. The trend observed by the rebound number followed that of the compressive strength. However, the non-destructive rebound hammer method gave significantly lower strength values than the destructive test method. The addition of fly ash had the effect of lowering the cost of producing the slab. However, the addition of fibres marginally increased the cost. The combined effect of fibre and fly ash resulted in a significant cost saving.
Numerical optimisation was carried out concerning the fibre reinforced concrete's fresh and hardened mechanical properties. Predictive modified quadratic equations were developed for slump value, compressive, flexural, split tensile strength and total cost. Analysis of variance test carried out for all the responses indicated that the model could predict the slump value and mechanical properties of the fibre reinforced concrete correctly and effectively with a coefficient of determination in the range of 0.4151 to 0.9467. The developed model can predict the required fibre reinforced fresh and hardened properties in order to assist in decision making in construction in slabs. The optimum constituent combination for maximum mechanical strength at the lowest possible cost was found to be 15.7576 % Fly ash and 0.3232 % PET fibre with optimum responses as shown in Table 4-26. These predictions were validated experimentally, and a good correlation was observed between the actual and predicted values based on the observed standard deviations of 0.1335, 0.031, 0.005, 0.676, 0.02 for compressive strength, flexural strength, tensile strength, slump value and cost, respectively. Concrete slabs were optimised for various possible end uses, and the optimum PET fibre % and fly ash % were ascertained as shown in Table 4-27.
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Miljösystemanalys av amerikansk vapenfluga (Hermetia illucens) som fiskfoder : En studie av ett insektsbaserat fiskfoder i ett akvaponiskt systemHammarsten, Hanna January 2019 (has links)
Förenta nationerna förutser en global befolkningsökning med 2 miljarder människor till 2050, vilket motsvara en total befolkningsmängd på nära 10 miljarder människor. Dessutom förväntas ökningen ske oproportionerligt över jorden och koncentreras i delar av världen där livsmedelssäkerheten är låg och produktionen otillräcklig. FN:s livsmedels- och jordbruksorganisation (FAO) uppskattar att det kommer krävas en produktionsökning med 70% för att möta livsmedelsbehovet för den globala populationen. Att odla fisk som alternativ till konventionellt fiske är en möjlighet att möta den ökande efterfrågan på animaliskt protein då de naturliga fiskbestånden minskar. Akvaponiska odling är ett kombinerat odlingssystem av hydroponisk odling och vattenbruk som möjliggör minskade risker kopplade till övergödning och smitning. Dock är fiskodlingarnas konsumtion av foderfisk problematisk. Insekter är ett av många foderalternativ som ofta nämns som en klimatsmart lösning då insekter är platseffektiva att odla och har en hög förmåga att omvandla biomassa till högvärdigt protein. En art som fått extra mycket uppmärksamhet inom detta område är den amerikanska vapenflugan (Hermetia illucens). Syftet med denna studie var att undersöka om implementeringen av ett insektsbaserat fiskfoder med vapenflugelarver kan sänka klimat- och miljöpåverkan från en fiskodling jämfört med att använda ett konventionellt fiskfoder baserat på ingredienser från vildfångad havsfisk. Detta har gjorts genom utförandet av en litteraturstudie av det konventionella fiskfodret och en livscykelanalys av larvproduktionens påverkan inom dessa fyra miljöpåverkansindikatorer: total energianvändning, klimatpåverkan (GWP), foderfiskkonsumtion (FIFO) och försurning. Resultatet av studien visade att det framförallt är lokalen för produktionen som konsumerar energi för uppvärmning, ventilation och belysning. Utöver detta visade sig bearbetning av larverna (torkning) vara en energiintensiv process. Från klimatperspektiv är det själva komposteringsprocessen som förorsakar de största enskilda utsläppen av växthusgaser. Resultatet visar vidare att produktionen av den amerikanska fluglarven presterar bättre för de studerade faktorerna än det konventionella fiskfodret och att den således har potential som foderkomponent. Fallstudien visar att den undersökta akvaponianläggningen kan minska sin påverkan inom samtliga effektkategorier jämfört med ett nyttjande av konventionellt foder. Dock är studiens utfall beroende av vilka förutsättningar som finns gällande produktionens geografiska placering och således vilken elmix som nyttjas samt vilken tillgången är på lämpliga substrat såsom matsvinn. / The United Nations foresees a global population increase of 2 billion people by 2050, corresponding to a total population of nearly 10 billion people. In addition, the increase is expected to be disproportionate over the earth and concentrated to parts of the world where food safety is low and production insufficient. The Food and agriculture organization of the United Nations (FAO) estimates that a production increase of 70% will be required to meet the food needs of the global population. Growing fish as an alternative to conventional fishing is an opportunity to meet the increasing demand for animal protein as the natural fish stocks decrease. Aquaponics is a combined cultivation system of hydroponic cultivation and aquaculture that reduces risks associated with eutrophication, invasive species and diffusion of antibiotics and chemicals. However, the consumption of feed fish is problematic in in both traditional aquaculture and in aquaponic cultivation. Insects are one of many feed alternatives that are often referred to as a climate-smart solution since they are effective to grow from a land use perspective and have a high ability to convert biomass into high-quality protein. One species that has received extra attention in this area is the black soldier fly (Hermetia illucens). The purpose of this study has been to investigate whether the implementation of an insect-based fish feed with black soldier fly larvae can reduce the environmental impacts of an aquaponic cultivation farm compared to using conventional fish feed based on ingredients from wild-caught sea fish. This has been done by carrying out a literature study of the conventional fish feed and a life cycle analysis of the influence of larva production within these four environmental impact indicators: total energy use, climate impact (GWP), feed fish consumption (FIFO) and acidification. The results of this study showed that the main energy use for the production of larvae is energy for heating, ventilation and lighting of the production location. In addition, the processing of the larvae (drying) was showed to be an energy intensive process as well. From a climate perspective, it is the composting process carried out by the larvae that causes the largest individual emissions of greenhouse gases. The result also shows that the production of the black soldier fly larvae performs better within the four environmental impact indicators than the conventional fish feed and thus it has the potential as a more sustainable feed component. The case study shows that the analyzed aquaponic farm can reduce its impact in all studied impact categories compared to using conventional feed. However, the study's outcome depends on the current circumstances regarding geographical location of the production, the electricity mix used as well as the availability suitable substrates such as food waste.
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Why is Nature Able to Mold Some Phenotypes More Readily than Others? Investigating the Structure, Function and Evolution of ßeta-2 Tubulin in Drosophila MelanogasterGolconda, Sarah Rajini 31 May 2018 (has links)
No description available.
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Examining Hessian fly (Mayetiola destructor) management concepts and quantifying the physiological impact of hessian fly feeding on post-vernalization selected cultivars of winter wheat in KansasSchwarting, Holly N. January 1900 (has links)
Doctor of Philosophy / Department of Entomology / R. Jeff Whitworth / The Hessian fly, Mayetiola destructor (Say), has been a historically significant pest of wheat in Kansas. However, it has been 60+ years since research has been conducted examining the flies’ activity throughout the year. Results of pheromone trapping in 4 counties in Kansas shows that Hessian fly (HF) males are actively flying in the fall, at least 1 month after the historical fly-free dates. Therefore, the Hessian Fly-Free Date is no longer valid and should be referred to as the Best Pest Management Date. Using pheromones for fall and spring trapping also indicated that HF is more active throughout the spring than previously thought, with almost continuous fly emergence and numerous emergence peaks in both spring and fall. The use of resistant wheat cultivars has been adapted to protect seedling plants from HF larval feeding in the fall. However, it is unknown if these cultivars are still providing protection after winter vernalization. Greenhouse trials indicated that ‘Armour’, a cultivar considered intermediately resistant, remains resistant under infestation levels of 1 fly/tiller but significant seed weight losses occured under infestations of 3 flies/tiller. In the field, Armour did not provide protection post-vernalization, with plants containing similar numbers of flaxseeds (pupae) as the susceptible cultivar, ‘Fuller’, and having significant losses of culm height (cm), number of spikelets/spike, number of seeds/spike, and seed weight (grams) when infested. ‘Duster’, a cultivar considered highly resistant, appeared to provide resistance to HF larval feeding in both the greenhouse and the field, and even produced significantly heavier seeds when infested with 3 flies/tiller in the greenhouse. These results suggest that post-vernalization screening should be conducted on all HF resistant cultivars to determine if each continues to provide protection. Little information is available showing if and how HF larval feeding on more mature wheat (Feekes 7-10), post-vernalization, impact plants, aside from lodging. Greenhouse and field infestations of a susceptible cultivar, Fuller, showed that significant losses of culm height (cm), number of seeds/spikelet, and seed weight will result from as few as 1 larva /culm. Yield losses averaged 0.13g/spike (65 kg/ha) compared to non-infested plants.
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Hessian fly associated microbes: dynamics, transmission and essentialityBansal, Raman January 1900 (has links)
Doctor of Philosophy / Department of Entomology / Ming-Shun Chen / John C. Reese / Keeping in view the important roles of bacteria in almost every aspect of insect’s life, the current study is the first systemic and intensive work on microbes associated with Hessian fly, a serious pest of wheat crop. A whole body analysis of Hessian fly larvae, pupae, or adults suggested that a remarkable diversity of bacteria is associated with different stages of the insect life cycle. The overriding detection of genera Acinetobacter and Enterobacter throughout the life cycle of Hessian fly suggested a stable and intimate relationship with the insect host. Adult Hessian flies have the most dissimilar bacterial composition from other stages with Bacillus as the most dominant genus. Analysis of 5778 high quality sequence reads obtained from larval gut estimated 187, 142, and 262 operational taxonomic units at 3% distance level from the 1st, 2nd, and 3rd instar respectively. Pseudomonas was the most dominant genus found in the gut of all three instars. The 3rd instar larval gut had the most diverse bacterial composition including genera Stenotrophomonas, Pantoea, Enterobacter, Ensifer, and Achromobacter. The transovarial transmission of major bacterial groups provided evidence of their intimate relationship with the Hessian fly.
The Hessian fly is known to manipulate wheat plants to its own advantage. This study demonstrated that the combination of a decrease in carbon compounds and an increase in nitrogen compounds in the feeding tissues of Hessian fly-infested plants results in a C/N ratio of 17:1, nearly 2.5 times less than the C/N ratio (42:1) observed in control plants. We propose that bacteria associated with Hessian fly perform nitrogen fixation in the infested wheat, which was responsible for shifting the C/N ratio. The following findings made in the current study i.e. the presence of bacteria encoding nitrogenase (nifH) genes both in Hessian fly and infested wheat, exclusive expression of nifH in infested wheat, presence of diverse bacteria (including the nitrogen fixing genera) in the Hessian fly larvae, presence of similar bacterial microbiota in Hessian fly larvae and at the feeding site tissues in the infested wheat, and reduction in survival of Hessian fly larvae due to loss of bacteria are consistent with this hypothesis. The reduction in Hessian fly longevity after the loss of Alphaproteobacteria in first instar larvae, highest proportion of Alphaproteobacteria in insects surviving after the antibiotic treatments and the nitrogen fixation ability of associated Alphaproteobacteria strongly implies that Alphaproteobacteria are critical for the survival of Hessian fly larvae. This study provides a foundation for future studies to elucidate the role of associated microbes on Hessian fly virulence and biology. A better understanding of Hessian fly-microbe interactions may lead to new strategies to control this pest.
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South Africa Class F Fly Ash for roads : physical and chemical analysisHeyns, M.W., Hassan, M. Mostafa January 2013 (has links)
Published Article / Fly Ash is a by-product at thermal power stations, also otherwise known as residues of fine particles that rise with flue gases. An industrial by-product may be inferior to the traditional materials used construction applications, but, the lower the cost of these inferior materials make it an attractive alternative if adequate performance can be achieved. The objective of this study is to evaluate the chemical and physical effectiveness of self-cementing fly ashes derived from thermal power stations for construction applications with combined standards. Using laboratory testing specimens, suitable types of Fly Ashes namely: Kendal Dump Ash, Durapozz and Pozzfill, were tested to the required standards to evaluate the potential properties. All three Fly Ashes have been classified as a Class F Fly Ash, which requires a cementing agent for reactions to take place and for early strength gains in the early stages of the reaction processes. The Fly Ashes conformed to the combination of standards and have shown that the proper reactions will take place and will continue over period of time. The use of fly ash is accepted worldwide due to saving in cement, consuming industrial waste and making durable materials, especially due to improvement in the quality fly ash products.
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The immobilisation of organic waste by geopolymerisationGokhale, Charlene 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: In excess of24 x 106 tons (1997, Eskom) of coal-derived fly ash is produced annually
in South Africa for the production of electric power. A large quantity of this ash is
disposed of as a solid waste in landfills, thus posing a serious environmental problem.
Due to the shortage of landfill sites, new ways of utilising fly ash are needed.
Recently several authors have shown that various combustion fly ashes can be
converted into zeolites to obtain industrial products with applicability In
environmental management. Geopolymerisation has emerged during the last few
years as a possible solution to some waste stabilisation and solidification problems.
Phenolic compounds have been shown to be toxic to soil microorganisms at the partsper-
million level. Indeed several of the organic compounds classified by the U.S.
Environmental Protection Agency as priority pollutants, are phenols. Immobilisation
of phenols by adsorption on zeolites and encapsulation in a geopolymer appears to be
a promising solution to this problem.
This thesis reports a technique for the production of a low-silica sodium zeolitic
material from fly ash (zeolite NaP1), and its application for the stabilisation of
phenols by adsorption and subsequent encapsulation in a geopolymer matrix. A
commercial zeolite, clinoptilolite was also utilised as an adsorbent. Due to their
uniform pore sizes and large surface areas, zeoli tic materials are suitable for ion
exchange and adsorption of certain organic substances. Adsorption data show that the
commercial zeolite, clinoptilolite was an effective adsorbent for organics. Adsorption
data showed that between 51.2ppm and 74.3ppm of chlorophenol or between 15.4ppm
and 32.5ppm of phenol could be adsorbed. Physical encapsulation of the coated
zeolite loaded with organic within a geopolyrneric matrix increased the compressive
strength of the matrix from 28.80 kN to 40.79 kN. Leaching data for the various
geopolymer matrices with encapsulated and loaded zeolites show no organics being
leached from the system at a detection level of 2ppm. According to the SABS these
would have been acceptable organic concentrations within a waste water stream. In utilising waste materials (fly ash and organic waste) and their reactive properties, it
is now possible to create various geopolyrners that are not only strong enough to be
used as constructionlbuilding materials, but are also effective immobilisation systems
for organic waste containment. / AFRIKAANSE OPSOMMING: Meer as 24 x 106 tons (1997, Eskom) vlieg-as word jaarliks deur die verbranding van
steenkool vir die produksie van elektrisiteit geproduseer. Die as, wat tans in groot
hoeveelhede as soliede afval in vaste-afval stortingsterreine gestort word, word gesien
as 'n groeiende omgewingsprobleem.
'n Tekort aan geskikte stortingsterreine maak die ontwikkeling van nuwe gebruike vir
die vlieg-as dringend nodsaaklik. Geopolimerisasie van vlieg-as materiale, 'n proses
wat die laaste paar jaar ontwikkel is, blyk 'n potensiele oplossing te wees vir sommige
afval stabilisering en solidifikasie toepassings.
Daar is bewyse dat fenoliese verbindings, selfs op 'n dele per miljoene (dpm) vlak,
toksies is vir grondorganismes. Verskeie van die komponente wat deur die
Amerikaanse Omgewingsbeskermingsagentskap (US EPA) as prioritats kontaminants
geklassifiseer is, is ondermeer fenole. Die huidige werk ondersoek die adsorbsie van
fenol op zeoliet NaPI en clinoptiloliet, gevolg deur fisiese omsluiting deur
geopolimerisasie.
Verskeie outeurs het onlangs verwys na die omsetting van verskeie verbrandings
vlieg-asse na zeoliete om bruikbare industriele produkte (vir gebruik in die
omgewingsveld) te vorm. Die tesis rapporteer 'n metode vir die produksie van 'n iae
silika natrium zeolitiese material (zeoliet NaP!) uit vlieg-as en die gebruik daarvan in
die stabilisering van fenole. 'n Kommersieel beskikbare zeoliet, clinoptiioliet, is ook
gebruik as adsorbent. Uniforme porie groottes en hoe oppervlak areas maak zeolitiese
materiale geskik vir ioonuitruiling, asook die adsorbsie van verskeie orgamese
verbindings. Deur die fisiese omsluiting van die zeolitiese materiaal binne 'n
geopolimeer matriks, kan materiale met beduidend hoe druksterktes, geproduseer
word. Adsorbsie data het getoon data die kornmersiele zeoliet, klinoptilotiet, 'n
effektiewe adsorbent vir organiese stowwe is. Adsorbsie waardes het gewissel tussen
51.2dpm tot 74.3dpm vir chlorofenol en 15.4dpm tot 32.5dpm vir fenol. Fisiese
enkalsulering van die bebandelde zeoliet (coated fzeo) binne 'n geopolimeer matriks het die saamdrukbaarheidsterkte van die betrokke matriks verhoog van 28.80 kN to
40.79 kN. Logingsdata verkry vir die onderskeie geopolimeer matrikse het getoon dat
geen van die organiese stowwe uit die matrikse vrygestel word nie. Indien die
organiese stowwe wel vrygestel sou word, sou die waterfase konsentrasie onder 2
dpm, binne die aanvaarbare spesifikasie vir uitvloeisels volgens die SABS standard,
gewees het.
Verskeie geopolimere, wat nie slegs sterk genoeg is om as konstruksie materiale te
dien nie, maar addisioneel effektief as immobilisasie medium dien, kan dus uit die
reaktiewe eienskappe van afval materiale (vlieg-as en organiese afval) vervaardig
word.
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Sustainable utilisation of raw sewage sludge (RSS) as a water replacement in cement-based materials containing unprocessed fly ashHamood, Alaa January 2014 (has links)
Prior to the implementation of the European Union Urban Waste Water Treatment Directive (91/271/EEC) in 31 Dec 1998, around a quarter of the sewage sludge produced in the UK was either discharged to surface waters via pipes or disposed from ships at sea. Discontinuing this route together with the quality requirements of the European Waste Water Directive, led to the generation of significant quantities of sewage sludge. It has therefore become required to treat this waste effectively before it can be sent back to the environment. Consequently, this added greater challenges for the environmental agencies, as well as local authorities. The treatment process comprises costly and energy consuming applications including physical, chemical, biological and thermal. In addition to the sewage sludge, the power generation industry produces massive quantities of fly ash from burning coal. In the UK, there is about 5,300,000 tonnes of fly ash that are generated annually, which require to be processed and classified in order to meet the standard requirements before it can be used in the construction applications. The classifying process also involves a series of costly and energy consuming mechanical and physical applications. This research programme has introduced an innovative alternative to the traditional re-use and disposal routes of Raw Sewage Sludge (RSS) and unprocessed fly ash. It has suggested the utilisation of RSS and unprocessed fly ash as raw ingredients for the production of sustainable construction materials. This research programme has therefore examined the performance of cement-based materials containing Raw Sewage Sludge (RSS) as a water replacement and unprocessed fly ash as cement replacement. Mortar and concrete mixes incorporating these materials were tested for their flowability/workability, density, Total Water Absorption (TWA), Ultrasonic Pulse Velocity (UPV), compressive strength, flexural strength, drying shrinkage, sulphate attack and leaching properties. Three series of cement-based materials were studied including mortar mixes with RSS and unprocessed fly ash (Series 1), mortar mixes with RSS and large proportions of unprocessed fly ash (Series 2), and concrete mixes with RSS and unprocessed fly ash (Series 3). The outcomes of the investigation were encouraging in that cement-based materials containing RSS and unprocessed fly ash that were produced demonstrated relatively good engineering, durability and environmental properties in comparison to the control mixes. The inclusion of unprocessed fly ash significantly reduced flowability/workability; however it improved long-term compressive strength for both mixes with RSS and water. The best compressive strength results were recorded when cement was replaced with 10-20% unprocessed fly ash by weight of total binder. The results also showed that sulphate attack resistance improved when fly ash was included. Moreover, safe concentration levels of heavy metals and free ions were detected when leaching test was performed. However, it must be kept in mind that more environmental tests must be performed before any large scale use is undertaken.
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Industrial Pilot Scale Leaching and Recovery of Zinc from Waste-to-Energy Fly Ash using Scrubber LiquidsWagner, Manuela January 2016 (has links)
Previous studies from laboratory experiments and a similar process at a plant in Switzerland, led to the pilot plant project at Renova AB, which will be described in this master thesis. In cooperation with Götaverken Miljö AB it was investigated if fly ash, produced at the Renova Waste-to-Energy plant in Gothenburg, could be treated with own scrubber liquids in order to recover zinc. If successful, Renova might build this tested pilot process in to a big scale. The pilot plant has a scale of 16 times smaller than a future big scale process. The goal of the project is to leach zinc from fly ash and gain a fly ash residue, which is classified as non-hazardous waste. The filtrate from the leaching campaign is treated so that the containing zinc is recovered. The zinc cake end product shall has a quality so that it can be sold to other industries or upgraded to high purity zinc metal. The evaluation of the experiments showed that the pilot plant process was successful. It was possible to leach out zinc by a maximum quote of 74%. The total recovery of zinc could be achieved by a maximum of 72%. The final zinc cake product was achieved through a precipitation and filtration campaign. This thesis evaluates, which process set-ups for zinc recovery through leaching and precipitation & filtration are the best and can be recommended for a big scale process. In addition, it briefly analyses the zinc product quality. Future studies will be necessary within: cost analysis of the process, zinc product quality and an analysis of the ash residue.
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The role of the mediterranean fruit fly, Ceratitis capitata, in Botrytis bunch rot of grapeEngelbrecht, Rene 03 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Botrytis bunch rot of grape is caused by Botrytis cinerea Pers. :Fr. Conidia of the
pathogen, which is dispersed by wind, water droplets and by insects, can penetrate the intact
grape berry cuticle, but disease expression occurs only under predisposing conditions. Since
relatively high infection rates often occur in vineyards, predisposing factors must play a
fundamental role in primary infection and subsequent disease occurrence. Insects can play a
very important role in this regard by depositing inocula at wound sites during feeding and by
providing fresh wounds during their oviposition and feeding activities. The aim of this study
was (i) to determine the potential of the Mediterranean fruit fly to transfer B. cinerea and
other bunch and fruit rot fungi in natura, (ii) to investigate the transport, deposition and
subsequent disease expression on grape berries in vitro, and (iii) to investigate fruit fly
activities and the nature of deposited conidia and mycelia of B. cinerea by aid of digital
photography and epifluorescence microscopy, respectively.
Two Sensus fruit fly traps containing the para-pheromone, Capilure, were installed in
orchards and five neighboring vineyards on four farms in the Stellenbosch region. Ceratitis
fruit flies were collected weekly, identified and counted to determine the fluctuations in fruit
fly population. Following field collection, the fruit flies were plated on Kerssies' B. cinerea
selective medium and the number of flies yielding the pathogen was recorded. Two fruit fly
species, C. capitata and C. rosa, were captured during the study period. Ceratitis rosa
numbers comprised only 1% of the total number of fruit flies captured. Ceratitis capitata
numbers, and the percentage B. cinerea contaminated flies generally increased after harvest in
the different orchards and vineyards. Following harvest, the percentage flies yielding B.
cinerea was higher in vineyards compared to orchards. Furthermore, in each vineyard an
increase in percentage B. cinerea contaminated fruit flies was preceded by a corresponding
increase in its neighboring orchard. The levels of both Penicillium and Alternaria
contaminated fruit flies stayed high throughout the investigation period, especially after
harvest of the orchard cultivars. Low incidence of Aspergillus, Mucor and Rhizopus spp.
were recorded on C. capitata. These findings suggest that the Mediterranean fruit fly may play an important role in the dispersal of inocula of fungi associated with postharvest decay
from early-maturing stone fruit orchards to mid- and late-maturing wine grape vineyards, and
in disease induction under conditions unfavourable for natural infection.
Three experiments were conducted to determine the potential of fruit flies in provoking B.
cinerea decay. In the first experiment, transport of conidia and disease expression were
investigated on rachis segments bearing unwounded berries only. In the second experiment,
the effect of wounding on disease expression was investigated. In the third experiment, the
effect of inoculum type (mycelia and conidia) on transportation and disease expression was
investigated on rachis segments bearing unwounded berries, and on segments with wounded
berries. The table grape cultivar, Dauphine, and the wine grape cultivar, Shiraz, were used at
véraison, two weeks before harvest and harvest, and the transport studies were conducted in
ethanol-disinfected perspex cages. Disease expression was studied in dry (~56% RH),
ethanol-disinfected perspex chambers incubated at 22°C. The isolations from berries revealed
that the flies deposited, without preference, high amounts of B. cinerea at various positions on
the grape berry's surface. The freezing studies showed that the deposited conidia germinated
and penetrated the berry skin at various positions. However, B. cinerea developed more often
at the pedicel end than on the cheek or style end, which indicated a peculiar interaction
between B. cinerea, the fruit fly and host tissue at this part of the berry. This phenomenon
was substantiated by the finding that B. cinerea also developed more often at the pedicel end
of berries that were not frozen. Further evidence for this interaction was found on intact
berries exposed to flies that carried mycelia after feeding on berries without sporulating
colonies of the pathogen, but showing symptoms of slippery skin. Significantly more decay
developed on wounded berries compared to the unwounded berries and more so at the wound
site. In addition, female fruit flies were responsible for significantly more decay development
than male fruit flies. The study thus proved that the Mediterranean fruit fly can promote B.
cinerea disease development under conditions unfavorable to natural infection.
The activities of the Mediterranean fruit fly, Ceratitis capitata, on grape berries were
monitored by aid of digital photography. In addition, the deposition of conidia and mycelia of
Botrytis cinerea at three sites (pedicel end, cheek and style end) on the grape berry,
germination of the fungal structures after dry (±56% RH) and moist (±93% RH) incubation
and wounds inflicted during ovipositioning were examined with an epifluorescence
microscope. The observations revealed that the fruit fly's activities were generally restricted to the grape berry. They visited the grape berry cheek more often, but visitations to the
pedicel end of berries increased substantially from véraison to harvest, indicating the
possibility of nutrient leakages at this site. Microscopy revealed that the flies deposited
conidia singular, in feeding packages and in faecal excrements on the berry surface. The
conidia in feeding packages were ensheathed by salivical fluids and occurred in clusters of 10
to 50 conidia. An average of 60% of the conidia in feeding packages germinated under dry
conditions (±56% RH). Conidia that passed through the intestinal tract of the fruit fly and that
were deposited in faecal excrements were deformed and low in viability. These conidia did
not occur in cluster format, but were proportionally spread with the faeces on the surface of
the grape berry. Conidia that were deposited singular and in faecal excrements did not
germinate unless incubated under moist conditions (± 93% RH). Wounds inflicted by female
fruit flies during ovipositioning were most frequently observed on the cheek. This
predisposition to B. cinerea infection of grape berries by the activities of fruit flies, suggested
an important role for the flies in the initiation of Botrytis bunch rot epidemics in vineyards. / AFRIKAANSE OPSOMMING: DIE ROL VAN DIE MEDITERREENSE VRUGTEVLIEG, CERATITIS CAPITATA,
IN BOTRYTIS CINEREA TROSVERROTTING VAN DRUIWE
Botrytis-trosverrotting van druiwe word deur Botrytis cinerea Pers. :Fr. veroorsaak.
Konidia van die patogeen wat deur wind, waterdruppels en insekte versprei word, kan die
intakte druiweskil binnedring, maar siekte-uitdrukking vind slegs onder spesiale
omstandighede plaas. Aangesien relatief hoë infeksie vlakke algemeen in wingerde voorkom,
moet predisponerende faktore 'n fundamentele rol in die primêre infeksie, en die daaruit
voortspruitende siektetoestand speel. Insekte kan 'n baie belangrike bydrae lewer deur
inokuia tydens voeding by wonde te deponeer. Nuwe wonde kan ook tydens oviposisionering
en voeding ontstaan. Die doel van hierdie studie was om (i) die potensiaal van die
Mediterreense vrugtevlieg om B. cinerea en ander tros- en vrugverrottingswamme in natura
oor te dra, te bepaal; om (ii) die verspreiding, deponering en daaropvolgende siekteuitdrukking
op druiwekorrels in vitro te ondersoek; en om (iii) die aktiwiteite en aard van die
gedeponeerde konidia en miselia met behulp van digitale fotografie sowel as epifluoressensiemikroskopie
waar te neem.
Twee Sensus-vrugtelokvalle met die paraferomoon, Capilure, IS In vrugteboorde en
aangrensende wingerde in die Stellenbosch-omgewing aangebring. Ceratitis-vrugtevlieë is
weekliks versamel, geïdentifiseer en getel om fluktuasies in die vrugtevliegpopulasie te
bepaal. Na die veldversameling is die vrugtevlieë op Kerssies se B. cinerea-selektiewe
medium uitgeplaat. Gedurende die studie is twee spesies vrugtevlieë, C. capitata en C. rosa,
gevang. Na oesstyd het die aantal Ceratitis-vrugtevlieë en die persentasie vrugtevlieë, besmet
met B. cinerea, in die verskillende boorde en wingerde toegeneem. Na oestyd was die
persentasie vrugtevlieë wat B. cinerea gedra het, hoër in die wingerde as in die boorde. Elke
toename in die persentasie B. cinerea-besmette vrugtevlieë in 'n wingerd is voorafgegaan
deur 'n ooreenkomstige toename in die aangrensende vrugteboord. Die aantal vrugtevlieë
besmet met Penicillium en Alternaria spp. het tydens die navorsingstydperk deurgaans hoog
gebly, veral nadat die vrugteboord-kultivars geoes is. Die voorkoms van Aspergillus-,
Mucor- en Rhizopus spp. op Ceratitis-vrugtevlieë was deurgaans laag. Hierdie bevinding wys
daarop dat vrugtevlieë 'n belangrike rol speel in die verspreiding van swarninokula, wat met na-oes verrotting geassosieer word, van vroegrypwordende steenvrugteboorde na mid- en
laatrypwordende wyndruifwingerde.
Drie eksperimente is in vitro onderneem om vrugtevlieë se potensiaal om B. cinereaverrotting
te veroorsaak te bepaal. In die eerste eksperiment is ragi met slegs ongewonde
korrels gebruik om die oordrag van konidia en siekte-ontwikkeling te ondersoek. In die
tweede eksperiment is die effek van verwonding op siekte-ontwikkeling ondersoek. In die
derde eksperiment is die effek van inokulumtipe (miselia en konidia) op verspreiding en
siekte-ontwikkeling ondersoek deur ragis-segmente met gewonde korrels sowel as ragissegmente
met ongeskonde korrels te gebruik. Die tafeldruif-kultivar Dauphine en die
wyndruif-kultivar Shiraz, by kleurbreuk, twee weke voor oes en by oestyd, is in die
eksperimente gebruik. Die oordragstudies is in etanol-ontsmette perspex-hokke uitgevoer.
Siekte-ontwikkeling is bestudeer in droeë (±56% RH), etanol-ontsmette perspex-kamers en
geinkubeer by 22°C. By ondersoek is gevind dat vlieë, sonder voorkeur, groot hoeveelhede
B. cinerea op verskeie dele op die druiwekorrel-oppervlak deponeer. Bevriesingstudies het
aangetoon dat die gedeponeerde konidia op verskeie dele van die korrelontkiem en die skil
binnedring. Botrytis cinerea het egter meer dikwels by die korrelsteelkant as by die
stempelkant, of op die wang, ontwikkel. Hierdie bevinding het 'n eiesoortige interaksie
tussen B. cinerea, die vrugtevlieg en gasheerweefsel by die korrelsteelkant van die korrel
aangetoon. Die verskynsel is gestaaf deur die bevinding dat B. cinerea ook meer dikwels by
die korrelsteelkant van die korrels wat nie gevries is nie, ontwikkel het. Verdere bewys van
hierdie interaksie is gevind by ongeskonde korrels wat aan die vlieë wat miselia gedra het
blootgestel is. Die siekte het beduidend meer dikwels op gewonde as ongewonde korrels en
verder aansienlik meer dikwels op die wondoppervlakte ontwikkel. Dit was ook duidelik dat
vroulike vrugtevlieë baie meer vir verrotting verantwoordelik was as manlike vrugtevlieë.
Die studie bewys dus dat Mediterreense vrugtevlieë die ontwikkeling van B. cinerea kan
bevorder in omstandighede wat ongunstig is vir natuurlike infeksie.
Die aktiwiteite van die Mediterreense vrugtevlieg C. capitata op die druiwekorrels is met
behulp van digitale fotografie waargeneem. Verder is die deponering van konidia en miselia
van B. cinerea op die verskillende dele (korrelsteelkant, wang en stempelkant) van die korrel,
ontkieming van die swamstrukture na droeë (±56% RH) en nat (±93% RH) inkubasie en
wonde wat tydens oviposisionering veroorsaak is, met epifluoressensie-mikroskopie
ondersoek. Die waarnemings het onthul dat die vrugtevlieg se aktiwiteite gewoonlik tot die druiwekorrel beperk is. Hulle het korrelwange meer dikwels besoek. Besoek aan die
korrelsteelkant het aansienlik toegeneem van kleurbreuk tot oestyd, wat op die moontlikheid
van voedingstof-lekkasie by die deel aandui. Mikroskoopstudies het aangedui dat vlieë
konidia enkel, in voedingspakkies en in fekale uitskeidings op die korreloppervlakte
deponeer. Die konidia in die voedingspakkies is deur speekselvloeistof omhul en het in
groepe van 10 tot 50 konidia voorgekom. Gemiddeld 60% van die konidia in
voedingspakkies het in droeë omstandighede (±56% RH) ontkiem. Konidia wat deur die
spysverteringskanaal van die vrugtevlieg gegaan het en in die fekale ekskresie gedeponeer is,
was misvorm en het lae lewensvatbaarheid gehad. Laasgenoemde konidia was nie in groepe
gedeponeer nie, maar is proporsioneel met die feces op die oppervlak van die druiwekorrel
versprei. Konidia wat enkel en in feces gedeponeer is, het nie ontkiem nie, tensy toestande
vogtig (±56% RH) was. Wonde wat deur die vroulike vrugtevlieë tydens oviposisionering
veroorsaak is, is meer dikwels op die wang van die korrelopgemerk. Hierdie predisposisie
van druiwekorrels tot B. cinerea-infeksie, meegebring deur die aktiwiteit van die vrugtevlieg,
dui daarop dat die rol wat die vrugtevlieg in die inisiëring van Botrytis trosverrottingepidemies
in wingerde speel, van beduidende belang is.
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