1,720,958 research outputs found
Control of the woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), using entomopathogenic fungi
Get PDFThesis (MScConsEcol)--Stellenbosch University, 2019.ENGLISH ABSTRACT: Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), or woolly apple aphid (WAA), is a serious pest of apple trees (Malus domestica Borkhausen), attacking both the root system and the arboreal parts of the tree. Current management of WAA in apple orchards relies on the use of both biological and chemical control. However, biological control using the principal parasitoid of the WAA, Aphelinus mali (Heldemann) (Hymenoptera: Aphelinidae), was found to be ineffective. The use of chemical control has also proven to be negative, as biotypes of the WAA have developed resistance to the chemicals used.
The use of entomopathogenic fungi (EPF) has been identified as promising biological control method against a wide array of insect pests. The main aim of the current study was to conduct a survey of EPF in the local apple orchards of the Western Cape province, and to screen their ability to control the root colonies of the WAA, under optimum laboratory conditions. The above was achieved by collection of soil and WAA-infested root samples from six apple farms. The EPF were baited from collected soil samples, using susceptible insect hosts, and directly from WAA females collected from the infested root samples. Successfully isolated fungi were grown on agar plates and screened for their pathogenicity against insects. The isolated EPF were identified both morphologically and molecularly, which include Beauveria bassiana, Isaria fumosorosea, Metarhizium brunneum, Metarhizium pinghaense, Metarhizium robertsii and Purpureocillium lilacinum.
The second aim of the study was to screen the six isolated EPF for their virulence against the WAA under optimum laboratory conditions. The above was achieved by conducting screening, concentration-dose-response and exposure-time-response bioassays. Metarhizium pinghaense and M. brunneum proved to be the most effective species against the root colonies of WAA, indicating that the local isolates of EPF have potential for the biological control of the WAA.
The final aim of the current study was to test for the persistence of M. pinghaense and M. brunneum on apple bark over a period of 3 weeks under laboratory conditions, and to determine whether the fungal conidia would attach to crawlers, or the fourth-stage nymphs, of the WAA as they move up tree trunks from the roots to the aerial parts of the apple trees. The above was done by means of spraying apple bark with a standard conidial concentration of 1.0 x 107 conidia/ml of both M. pinghaense and M. brunneum, respectively. The persistence of fungal conidia on the apple bark was measured using codling moth larvae as an indicator. The results indicated M. pinghaense to have better persistence on the apple bark over a period of 3 weeks than did M. brunneum. Further analysis of persistence, whereby the root colonies of the WAA were exposed to the dried conidia of M. pinghaense on apple bark, showed that M. pinghaense was capable of inducing mortality of about 39-82% in colonies of WAA under optimum laboratory conditions, when exposed for a period of 10 days.
The current study has highlighted both the diversity of soilborne EPF in the local apple orchards of the Western Cape, and their potential to be successfully integrated in managing the presence of the WAA colonies in apple orchards. The local isolate of M. pinghaense has shown to be the best candidate for managing WAA. Therefore, future research should focus on testing the efficacy of the local isolate of M. pinghaense against the WAA, under both glasshouse and field conditions.AFRIKAANSE OPSOMMING: Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), ook bekend as die appelbloedluis (WAA), is ʼn ernstige pes van appelbome (Malus domestica Borkhausen) wat skade veroorsaak aan die wortelstelsel, takke en blare. Die luis word tans bestuur in appelboorde deur die gebruik van chemiese en biologiese beheermiddels. Biologiese beheer deur die gebruik van die hoofparasiet van die WAA, Aphelinus mali (Heldemann) (Hymenoptera: Aphelinidae), is egter getoets en daar was gevind dat dit oneffektief is in die beheer van die luis. Daar was ook bewys dat die gebruik van chemiese middels oneffektief is, aangesien sommige biotipes van WAA weerstand ontwikkel het teen die chemikalieë wat gebruik word.
Die gebruik van entomopatogeniese swamme (EPF) is geïdentifiseer as ʼn belowende, effektiewe metode vir die beheer van verskeie insek peste. Die huidige studie was gefokus daarop om ʼn opname te doen van EPF in die plaaslike appelboorde van die Wes-Kaap provinsie en dan te toets of hul die vermoë het om wortel kolonies van WAA te beheer in optimale laboratorium omstandighede. Om dit te toets, was grond en wortels wat geïnfekteer was met WAA, versamel van ses appelplase. Die EPF was toe geïsoleer van die grondmonsters deur vatbare insekte te gebruik as lokinsekte. EPF is ook geïsoleer van die wortels deur WAA wyfies te versamel vanaf die geïnfekteerde wortelmonsters. Swamme wat suksesvol geïsoleer is, is dan gegroei op agarplate, waarna hul vermoë om insek peste te beheer getoets is. Die EPF wat geïsoleer is, is geïdentifiseer deur morfologiese en molekulêre tegnieke en sluit in Beauveria bassiana, Isaria fumosorosea, Metarhizium brunneum, Metarhizium pinghaense, Metarhizium robertsii en Purpureocillium lilacinum.
Die tweede doelwit van die studie was om die effektiwiteit van die ses geïsoleerde EPF te toets op appelbloedluise in optimale laboratorium omstandighede. Om dit te toets was die EPF aangewend teen verskillende konsentrasies en die appelbloedluise blootgestel aan die swamme vir verskillende tydperke. Die twee EPS spesies, Metarhizium pinghaense en M. brunneum was mees effektief teen die wortel kolonies van ABL, wat beteken dat die plaaslike EPS isolate potensiaal het vir die beheer van die ABL.
Die derde doelwit van die studie was om te toets of M. pinghaense en M. brunneum kan oorleef op appelboombas vir ʼn periode van drie weke in optimale laboratorium omstandighede, asook om vas te stel of die swamme se spore kan vassit aan die kruipers of die vierde stadium nimfe soos wat hul op beweeg teen die boomstam vanaf die wortels na die takke. Om bogenoemde te toets, was appelboom bas gespuit deur gebruik te maak van ʼn standaard spoor konsentrasie van 1.0 x 107 spore/ml van M. pinghaense of M. brunneum. Die oorlewing van die swam spore op die bas was getoets deur kodlingmot larwes te gebruik as indikatore. Die resultate het getoon dat M. pinghaense langer infektief gebly het op die bas as M. brunneum, oor ʼn tydperk van 3 weke. Verdere analises is uitgevoer waar die wortel kolonies van die WAA blootgestel is aan die gedroogde spore van M. pinghaense op appel bas en het getoon dat M. pinghaense in staat was om sterftesyfers van 39-82% te veroorsaak in WAA kolonies, na blootstelling vir 10 dae, in optimale laboratorium omstandighede.
Die huidige studie beklemtoon die diversiteit van EPF in die plaaslike appelboorde van die Wes-Kaap, asook hul potensiaal om suksesvol geïntegreer te word in die bestuur van WAA getalle in appelboorde. Die studie het getoon dat die plaaslike isolaat, M. pinghaense, die beste kandidaat is uit die wat getoets is, vir die beheer van WAA. Toekomstige navorsing moet dus fokus daarop om die effektiwiteit te toets van M. pinghaense teen WAA in beide glashuis- en veld omstandighede.Master
Control of the obscure mealybug, Pseudococcus viburni (Hemiptera: Pseudococcidae) using entomopathogenic fungi and nematodes
Get PDFThesis (PhDConsEcol)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), the obscure mealybug, is a serious
cosmopolitan, polyphagous agricultural insect pest of deciduous fruit crops. In South
Africa, the mealybug negatively affects apple and pear production. Feeding of the mealybug on the
arboreal parts of fruit trees results in different types of damage, such as early flower and fruit
drop, leaf and fruit discoloration and, in severe cases, the premature death of the host plant
shoot. On apples and pears, various life stages of the mealybug are often found in the fruit core
and calyx, and on the pedicel. The mealybug extracts and ingests large amounts of phloem sap when
feeding, then excretes the excess sap as a carbohydrate-rich sugary substance, which is known as
honeydew, which falls onto the fruit, leaves and bark. This results in severe secondary damage, as
it promotes the growth of sooty mould. Infestation of the fruit and the presence of sooty
mould on the fruit have severe economic implications, as both stained and infested
fruits are likely to be rejected or downgraded in pack- houses. Currently, the management
of obscure mealybug in orchards relies on the use of both biological and chemical
control. However, current management strategies have proven to be ineffective, as the
mealybug has developed resistance to a range of chemical insecticides. Both
entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPN) are effective biological
control agents of various agricultural insect pests, as they cause epizootics in various insect
orders. The main aim of this study was to assess the potential of both local and commercial EPF
species and of local in vivo- and in vitro-cultured species of EPN as possible
biological control agents of P. viburni. The pathogenicity of the entomopathogens was assessed
under laboratory conditions, with the EPF being tested at a conidial concentration of 1 × 10⁷
conidia/ml, and EPN at a concentration of 200 infective juveniles (IJs) per insect. From the study,
two local EPF isolates, namely Metarhizium pinghaense (5HEID) and M. robertsii (6EIKEN) were
identified as the most effective EPF isolates against P. viburni, resulting in >90% insect
mortality, a week after exposure to the entomopathogens. The local in vivo-cultured Heterorhabditis
indica (SGS) was found to be the most effective EPN isolate against P. viburni, causing 79% insect
mortality, 48 h post inoculation. Further evaluation assessing the effect of combined application
of M. pinghaense or M. robertsii with H. indica against
P. viburni was conducted under laboratory conditions, using both sequential and
simultaneous exposure methods. For the sequential method, the entomopathogens were each applied in
turns, using first either the EPF or the EPN, followed by the other entomopathogen, at different
time intervals. For the simultaneous method, the mealybugs were exposed to both EPN and EPF
simultaneously. The combined application of H. indica with M. pinghaense or M. robertsii was
observed to result in increased mortality of P. viburni, relative to when they were applied
individually. The simultaneous
application of H. indica and M. pinghaense was the most effective combination method of the two
entomopathogens against P. viburni, resulting in 95% mortality five days post
inoculation. The
sequential method of application of H. indica and M. robertsii was the most effective, resulting in
>85% mortality of P. viburni after four and three days of exposure. The interaction
between the entomopathogens, when used in combination, was found to have an additive effect in all
combination exposures. The infective conidia of M. pinghaense and M. robertsii were mass
cultured, using agricultural grains as solid substrates. Rice grains, inoculated using
blastospores, were the best for mass culture and production of conidia of both M. pinghaense and M.
robertsii. Oil carriers (liquid paraffin, coconut oil, canola oil and olive) and a mineral
carrier (diatomaceous earth) were investigated as potential formulations for mass-produced
conidia of both M. pinghaense and M. robertsii. The viability of the formulated conidia was
assessed over a period of eight weeks, and the efficacy of the formulation against P. viburni being
assessed at the end of eight weeks. Oil carriers were found to be the most effective formulation
for conidia of both the fungal isolates, maintaining conidial viability of >95% over time.
The conidia in all the oil formulations also induced high mortality, ranging between 60%
and 90% for M. pinghaense, and 70% and 90% for M. robertsii, when used against P. viburni. The
current study provides insight into the efficacy of both EPF and EPN as possible biological control
agents of P. viburni. Further long-term evaluation of the efficacy of the tested isolates of
M. pinghaense, M. robertsii and H. indica, used individually or in combination, against
P. viburni under field conditions, will provide insight into the potential success of using the
entomopathogens for the management of the mealybug in orchards, as well as providing information
regarding the possible integration of the entomopathogens as biocontrol agents in an
integrated pest management system against mealybugs.AFRIKAANSE OPSOMMING: Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), die appelwitluis, is ʼn
ernstige kosmopolitiese insekpes van landboukundige gewasse, veral van sagtevrugte. In
Suid-Afrika het hierdie witluise veral ʼn negatiewe invloed of appel- en peerproduksie. Voeding van
die witluis op die blare en vrugte kan lei tot ʼn reeks van skade, soos vroeë blom- en vrugval,
verkleuring van blare en vrugte en, in ernstige gevalle, die vroegtydige dood van die gasheerplant.
Op appels en pere word verskillende lewensfases van die witluis dikwels aangetref in die vrugkern
en –kelk, sowel as op die stam. Die witluise neem groot hoeveelhede floëemsap op tydens voeding en
skei dan oortollige sap uit as heuningdou, ʼn koolhidraatryke suikerstroop, wat op die
vrugte, blare en bas aanpak. Heuningdou kan lei tot sekondêre skade aangesien dit die groei van
roetskimmel bevorder. Infestasie deur witluise en die voorkoms van roetskimmel op die
vrugte het ernstige ekonomiese gevolge, aangesien gevlekte sowel as witluisbesmette vrugte in
pakhuise verwerp of afgradeer sal word. Tans berus die bestuur van appelwitluis in boorde op die
gebruik van beide chemiese en biologiese beheer. Die huidige beheerstratgieë, maar veral chemie, is
ondoeltreffend, aangesien witluise weerstand teen ʼn reeks insekdoders ontwikkel het. Beide
entomopatogeniese swamme (EPF) en nematodes (EPN) word as effektiewe biologiese beheermiddels van
verskillende landbou insekplae beskou, aangesien dit binne verskillende insekordes epidemies kan
veroorsaak. Die hoofdoel van hierdie studie was om die potensiaal van beide plaaslike en
kommersiële EPF-spesies, sowel as die plaaslike in vivo- en in vitro-geteelde spesies van EPN, as
moontlike biologiese bestrydingsagente van P. viburni te evalueer. Die patogenisiteit van die
entomopatogene is onder laboratoriumtoestande beoordeel, met die EPF wat getoets is teen 'n
spoorkonsentrasie van 1 × 10⁷ spore/ml en EPN teen 'n konsentrasie van 200 infektiewe larwes
(IJs) per insek. Uit die studie is twee plaaslike EPF-isolate van Metarhizium pinghaense
(5HEID) en M. robertsii (6EIKEN) geïdentifiseer as die mees effektiewe EPF-isolate teen P. viburni,
wat lei tot > 90% inseksterftes 'n week na blootstelling aan die entomopatogene. Die plaaslike in
vivo-geteelde Heterorhabditis indica (SGS) was die doeltreffendste EPN-isolaat teen P. viburni, wat
79% inseksterftes veroorsaak het, 48 uur na inokulasie. Verdere evaluering van die effek van die
gekombineerde toediening van die mees effektiewe EPF-isolate, M. pinghaense en M.
robertsii, met die effektiewe EPN-isolaat, H. indica, teen P. viburni is uitgevoer onder
laboratorium toestande, met behulp van beide opeenvolgende en gelyktydige kombinasie
blootstellingsmetodes. Vir die opeenvolgende metode is die entomopatogene om die beurt toegedien
deur eers die EPF of die EPN te gebruik, gevolg deur die ander entomopatogeen, met verskillende
tydsintervalle. Vir die gelyktydige metode is die witluise gelyktydig aan beide EPN en EPF
blootgestel. Die gekombineerde toediening van H. indica met M. pinghaense of M. robertsii het
gelei tot 'n toename in sterftes van
P. viburni, relatief tot wanneer dit afsonderlik toegedien is. Die gelyktydige toediening van H.
indica en M. pinghaense was die doeltreffendste kombinasiemetode van die twee entomopatogene teen P.
viburni, wat gelei het tot sterftes van 95%, vyf dae na inokulasie. Die
opeenvolgende toedieningsmetode van H. indica en M. robertsii was die doeltreffendste, wat tot meer
as 85% sterftes van P. viburni gelei het vier en drie dae na blootstelling. Daar is gevind dat die
interaksie tussen die entomopatogene in alle kombinasieblootstellings 'n additiewe effek
het. Massaproduksie van infektiewe spore van M. pinghaense en M. robertsii met verskeie
grane as soliede substrate is ondersoek. Ryskorrels, geïnokuleer met blastospore, het die beste
resultate vir massaproduksie van beide M. pinghaense en M. robertsii gelewer. Formulasies
van die massa geteelde spore van M. pinghaense en M. robertsii in oliedraers (vloeibare
paraffien, klapperolie, canola olie en olyfolie) en ‘n minerale draer (diatoomaarde) is
getoets om te bepaal wat die beste formulasie is om die patogenisiteit en raklewe
van massa geteelde swamspore vir toekomstige kommersiële veldtoediening teen P.
viburni te behou. Die lewensvatbaarheid en effektiwiteit van die spoorformulasies
teen P. viburni is vir beide EPF-isolate is oor 'n tydperk van agt weke ge-evalueer, Daar is gevind
dat oliedraers die doeltreffendste formulasie van die swamspore van beide die swam- isolate is, wat
meer as 95% lewensvatbaarheid behou. Die spore in al die olieformulasies het ook 'n hoë P. viburni
sterftesyfer veroorsaak, wat gewissel het tussen 60% en 90% vir M. pinghaense, en 70% en 90% vir M.
robertsii. Die huidige studie bied insig rakende die effektiwiteit van beide EPF en EPN as
moontlike biologiese beheeragente van P. viburni. Verdere lang termyn evaluering van die
doeltreffendheid van die getoetste isolate van M. pinghaense, M. robertsii en H.
indica, afsonderlik of in kombinasie aangewend, teen P. viburni onder veldtoestande word benodig.
Dit sal insig verskaf oor die moontlike sukses van die gebruik van entomopatogene vir die bestuur
van die witluis in boorde, asook inligting oor die moontlike integrasie van entomopatogene as
biologiese
beheeragente in 'n geïntegreerde plaagbestuurstelsel teen witluise.Doctora
Formulation of Metarhizium pinghaense and Metarhizium robertsii and the infection potential of the formulations against Pseudococcus viburni (Hemiptera: Pseudococcidae) after storage
No full textFormulation of entomopathogens refers to the mixing of various inert ingredients, like clays and mineral oils, with the active ingredients which are the entomopathogens. Successful formulation enhances the survival of the entomopathogen and also eases their transportation, storage, preparation and application. The aim of this study was to develop a formulation to maintain the longevity and pathogenicity of the mass-produced conidia of local Metarhizium pinghaense and M. robertsii, for above-ground future commercial field application against Pseudococcus viburni. The objectives were to develop a cost-effective protocol for formulation of infective propagules and to test their effectiveness under laboratory conditions. The conidia of both isolates were formulated using four different oils (liquid paraffin, coconut, canola and olive oils) as liquid carriers, and diatomaceous earth as a mineral carrier. Conidial viability and pathogenicity were assessed over a period of eight weeks. In the study, it was observed that the conidia formulated in oil carriers maintained a high conidial viability and survival rate of >95 % over a period of eight weeks for both isolates, relative to when formulated in mineral carriers, or when stored as dry conidial powder. The conidia in all the oil formulations were also observed to induce high mortality, ranging between 60 % and 90 % for M. pinghaense, and between 70 % and 90 % for M. robertsii, when used against P. viburni. The ability of conidia of both isolates to maintain viability and pathogenicity, following storage in the oil formulations, increased the likelihood of the local isolates being successfully integrated as biological control agents for management of P. viburni under field conditions
Infection of insects and persistence of Metarhizium (Hypocreales: Clavicipitaceae) species on apple bark
No full textEntomopathogenic fungi (EPF) are cosmopolitan soil borne pathogens that cause epizootics in various insect
orders. EPF isolates of Metarhizium brunneum and M. pinghaense have shown the potential for use as biological
agents of important agricultural insect pests. The aim of the current study was to test for the persistence of
M. brunneum and M. pinghaense on apple bark over a period of three weeks, under laboratory conditions. Apple
bark was sprayed with conidial suspensions of both fungi, at a standard infective conidial concentration of
107 conidia/ml. The persistence, or survival, of the conidia on apple bark was measured using codling moth
larvae (CM) (Cydia pomonella) and females of woolly apple aphid (WAA) (Eriosoma lanigerum) as indicator
species. The results showed that conidia of M. pinghaense can induce mortality of insect pests through contact
with an EPF-treated substrate, with mortality of 39% to 82% for WAA over a period of 10 days post application,
and with mortality of 3% to 68% for CM over a period of 7 days, after application to apple bark. Further
evaluation showed that the conidia of M. pinghaense persisted longer on apple bark, up to 63%, than did
M. brunneum, up to 11%, three weeks post application of the conidial suspensions. The study provides insights
into the potential persistence of fungal isolates on apple bark over time post application. Further evaluation of
the persistence of the isolates on apple bark under both glasshouse and field conditions should be conducted
The occurrence of entomopathogenic fungi in apple orchards and their biocontrol potential against Eriosoma lanigerum
No full textEriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), woolly apple aphid (WAA) is an important pest on apples globally and a key pest of apple production in South Africa. The aphid has developed some level of resistance against several chemical insecticides. Entomopathogenic fungi (EPF) have been identified as promising biological control agents against a wide array of insect pests. The main aim of this study was to conduct a survey in local apple orchards in the Western Cape province for EPF and to use isolates to test the susceptibility of WAA under optimum laboratory conditions. Soil samples were collected from apple orchards and EPF, baited and isolated using larvae of Galleria mellonella and Tenebrio molitor. Six EPF species: Beauveria bassiana, Cordyceps fumosorosea, Metarhizium brunneum, M. pinghaense, M. robertsii and Purpureocillium lilacinum were identified from the soil samples. The results from bioassays showed that Metarhizium robertsii and M. pinghaense isolates were the most effective with an average percentage mortality of > 90%. Metarhizium brunneum also proved to be effective when used against the insect with an average percentage mortality of > 80%, while B. bassiana and C. fumosorosea were the least effective with average percentage mortality of 52% and 48%, respectively. The LT50 and LT90 of M. robertsii (2.12; 4.19) and M. pinghaense (2.05; 4.45) showed to require similar mortality time in days of E. lanigerum. The results obtained in the study have provided an insight into the diversity of EPF species across apple orchards of the Western Cape and shown the efficacy of the Metarhizium isolates as potential biological control agents of the WAA
Effect of visible light and ultraviolet light on the pathogenicity of entomopathogenic fungi to false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae) larvae
No full textEntomopathogenic fungi (EPF) are effective and environment-friendly insect biological control agents. Ultraviolet (UV) light is known to have an effect on the survival of fungal conidia, and natural sunlight is potentially one of the most damaging factors undermining EPF persistence and pathogenicity. This study aimed to test the infection potential of an isolate of Beauveria bassiana and five Metarhizium species after exposure to different light treatments, on soil and leaf surfaces under laboratory and field conditions, using Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as the test host. Conidia were exposed either to growth light alone, which emits the same visible light as the sun, but excluding UV light, or directly exposed to UV light for 12 h. The results indicated no negative effect on the infection potential of the conidia of most species tested. The conidia of the two Metarhizium pinghaense (5HEID and TH149) isolates showed the greatest tolerance to visible light and UV radiation exposure on both soil and leaf surfaces. Exposure of M. pinghaense isolates to visible light on soil surfaces showed pathogenicity of > 80% for both isolates, and of between 58% and 88% after exposure to UV light. On leaf surfaces, three Metarhizium isolates, M. pinghaense (5HEID and TH149) and M. majus (TH153) had > 90% pathogenicity following exposure to UV light, and M. pinghaense (TH149) and M. robertsii (6EIKEN) showed greater tolerance of > 70%, under laboratory conditions. However, the pathogenicity of the EPF isolates was very low in field trials, indicating that further trials on the use of formulations and adjuvants with the isolates are needed to improve long-term persistence and efficacy under field conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
