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Effectiveness of trap crops for the control of stinkbugs (Heteroptera pentatomidae) in edible Cucurbitaceae species, in Limpopo Province, South AfricaLukhwareni, Humbulani 02 1900 (has links)
Four trap crops were tested for their ability to intercept stinkbugs (Heteroptera pentatomidae) in a cucurbit field crop at Waterpoort, Limpopo Province. The experimental trap crops were: Sunnhemp (Crotolaria juncea), okra (Abelmoschus esculentum), mustard mixture (Brassica hirta and Brassica juncea) and cowpea (Vigna unguiculata). The surveys were based on visual counts of stinkbugs from all the trap crops. Stinkbugs were collected from trap crops in a field crop trial of cantaloupe (Cucumis melo). The correlation between Brassica hirta and Brassica juncea with other trap crops had a great variance. The repeated B. hirta and B. juncea inner row experiment in 2012 interestingly lured the green stinkbug (Nezara viridula) into the cantaloupe field.
Amongst the entire trap crops, stinkbugs recovered from Brassica hirta and Bassica juncea, exceeded the average of the other three trap crops. The number of adult N. viridula captured had significantly increased in March 2012 and started to drop on the B. hirta and B. juncea mixture in the first week of April. During this increase, the crops were at the seeding stage.
The perimeter trap-cropping system practiced for all four trap crops varied in the attraction of stinkbugs along the perimeter of the field and inner row. B. hirta and B. juncea attracted a high number of N. viridula along the perimeter but fewer in the inner row. The B. hirta and B. juncea recorded the highest number of N. viridula in the inner rows and outer rows, compared to the other four trap crops, followed by V. ungiuculata. This study has demonstrated a significant potential of using trap crops as biological alternative for managing stinkbug pests in cucurbit crops. / Agriculture and Animal Health / M. Sc. (Agriculture)
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Quantification of spray coverage on grape bunch parts and the incidence of Botrytis cinereaBrink, Jan-Cor (Johannes Cornelius) 04 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Various studies revealed that Botrytis cinerea, the causal pathogen of Botrytis bunch
rot, is mostly associated with pedicels, rachises, laterals and berry bases, and not with berry
skins as previously understood. Provided that sufficient coverage of inner bunch parts was
achieved, laboratory studies have shown that fungicides can effectively reduce the amount of
B. cinerea at the various positions in bunches, and prevent infection and symptom expression
at all growth stages. The same efficacy was, however, not achieved with the same fungicides
when using conventional spraying methods in vineyards. Poor disease control on fruit and
leaves in vineyards is attributed to inappropriate timing of fungicide applications and/or
insufficient coverage of susceptible tissue. Previously, spray coverage evaluations in South
Africa were based on the use of water-sensitive cards. A variety of other methods have been
used to assess spray coverage in vineyards, but none of these methods could assess spray
deposits on a very small, three-dimensional area of interest such as the susceptible grape
bunch parts. The methods were furthermore dependent on human objectivity, which lacks
quantitative measuring and speed of measurement. Suitable technology to determine spray
coverage on susceptible bunch parts is, therefore, not available.
The aim of this study was to develop a protocol to visualise and quantify spray
deposits in grape bunches, specifically on the inner bunch parts and to use the protocol to
determine the effect of different levels of spray cover on artificially inoculated B. cinerea
grape bunches, in order to facilitate future determination of minimum effective coverage
levels for effective B. cinerea control.
A spray coverage assessment protocol using fluorometry, photomicrography and
digital image analyses was developed to measure spray coverage on susceptible grape bunch
parts. Among several fluorescent pigments tested, a yellow fluorescent pigment (SARDI
Fluorescent Pigment) from Australia was selected on the basis of its small particle size (2.45 -
4.90 μm). Bunches were sprayed at pea size and bunch closure with different volumes of a
mixture of fenhexamid and the yellow fluorescent pigment. Sprayed parts from bunches were
illuminated under black light (UV-A light in the 365 nm region) and visualised under a stereo
microscope at 20 x magnification. Photos of the berry skin, pedicel and rachis were taken
with a digital camera (Nikon DMX 1200). Image analysis of photos was done with Image-
Pro Discovery version 4.5 for Windows (Media Cybernetics) software. The total area of
deposited pigment in selected areas of interest (AOI) was calculated. The percentage area
covered was subsequently calculated for each AOI. Good correlation was evident between
the parameters, sum of objects and percentage area covered. Bunch parts at pea size generally
had higher coverage values than at bunch closure. Spray applications earlier in the season
would therefore result in higher and more effective spray coverage of the susceptible bunch
parts. Similar deposition trends were observed on the inner bunch parts (pedicel and rachis).
These were, however, significantly different from berry skins, which had significantly higher
levels of spray deposits than the inner bunch parts. The variance component analysis
indicated that the highest variance was observed for berries and bunches, and substantially
less for image readings. For the same accuracy, means for percentage coverage values of at
least 10 bunches per treatment (1 part per bunch and 3 readings per part) will be sufficient.
In order to determine the biological efficacy of different levels of spray coverage on B.
cinerea incidence on grape bunches, bunches were sprayed at pea size and bunch closure with
different volumes of a mixture of fenhexamid and a yellow fluorescent pigment and the
percentage fluorescent pigment coverage on pedicels was determine. Bunches were
subsequently dusted with dry airborne conidia of B. cinerea in a settling tower and incubated
for 24 h at high relative humidity (98%). Infection was determined by estimating the amount
of B. cinerea infections occurring on sprayed bunch parts with isolations on to paraquat and
Kerssies mediums. Linear regressions for the part x stage combinations of percentage B.
cinerea incidence on different bunch parts were fitted on mean coverage levels. An increase
in spray cover caused linear reductions in levels of B. cinerea on susceptible bunch parts.
Higher B. cinerea incidences were recorded at pea size. Furthermore, higher B. cinerea
incidences were found on paraquat medium for both stages, than on Kerrsies medium. The
information gathered from this study will be used to facilitate future determination of
minimum effective coverage levels for effective B. cinerea control in grape bunches.
In these validation experiments, the results clearly showed that the protocol can be
used to determine the effect of different levels of spray coverage on B. cinerea incidence and
that an increase in spray coverage will decrease B. cinerea incidence. The information
gathered from this study will be used to facilitate future determination of minimum effective
coverage levels for effective B. cinerea control in grape bunches and subsequently be used as
benchmarks to evaluate spray application in vineyards. / AFRIKAANSE OPSOMMING: Vaalvrot by wingerde word veroorsaak deur Botrytis cinerea. Verskeie studies het
getoon/gewys dat die oorsaaklike patogeen meestal geassosieer word met die pedisel, ragis,
laterale en die korrelbasis, en nie met die korrelskil soos voorheen beweer nie. Laboratorium
studies het getoon dat swamdoders wel effektief is om B. cinerea by alle trosdele te verminder
en simptoomontwikkeling te voorkom tydens alle groeistadia, mits die binne-trosdele
voldoende spuit bedekking ontvang het. Dieselfde effektiwiteit is egter nie gevind in
wingerde met konvensionele spuittegnieke nie. Onvoldoende siektebeheer van vrugte en
blare van wingerde kan toegeskryf word aan verkeerde spuit skedulering en/of swak
spuitbedekking van vatbare gasheerweefsel. Evaluering van spuitbedekking is voorheen in
Suid Afrika deur middel van water-sensitiewe papier gedoen. Verskeie ander metodes is al
gebruik om spuitbedekking te evalueer in wingerde, maar nie een van hierdie metodes kan
gebruik word om spuitbedekking op ’n baie klein, drie-dimensionele oppervlak, soos die
vatbare trosdele, te evalueer nie. Verder was die tegnieke afhanklik van menslike
objektiwiteit, en gevolglik ontbreek kwantitatiewe meting en metingspoed. Daar is dus nie
geskikte tegnologie vir die evaluering van spuitbedekking op vatbare trosdele nie.
Die doel van hierdie studie was die ontwikkeling van ‘n protokol vir die visualisering
en kwantifisering van spuitbedekking op spesifiek die binne-tros dele en om die protokol dan
te gebruik om die effek van verskillende vlakke van spuitbedekking op B. cinereageinokuleerde
druiwetrosse te bepaal,
Protokol vir evaluasie van spuitbedekking op vatbare druifdele is ontwikkel deur
gebruik te maak van fluorometrie, fotomikrografie en digitale beeldanalise. Van die
verskillende fluoresensie pigmente wat getoets is, is ‘n geel flouresensie pigment (SARDI
Flourescent Pigment) van Australië gekies op grond van sy klein partikelgrootte (2.45 - 4.90
μm). Druiwetrosse is gespuit tydens ertjie- en trostoemaakstadia met verskillende volumes
van ’n mengsel van fenheksamied en die geel fluorosensie pigment. Die gespuite druifdele is
dan verlig onder swartlig buise (UV-A lig in die 365 nm spektrum) en gevisualiseer deur ’n
stereo mikroskoop by 20x vergroting. Foto’s van die korrelskil, pedisel en ragis is met ‘n
digitale kamera (Nikon DMX 1200) geneem. Beeldanalise is gedoen met ImagePro
Discovery weergawe 4.5 vir Windows (Media Cybernetics) sagteware. Die totale area
neerslag van die pigment is in geselekteerde areas bereken. Die presentasie area bedek is
bereken vir elkeen van hierdie areas. Goeie korrelasie is gevind tussen die parameters aantal
fluoresserende partikels en die persentasie bedekte area. Trosdele tydens ertjie-stadium het in
die algemeen hoër waardes gehad as by trostoemaak. Dit blyk dus dat spuittoediening vroeg
in die seisoen meer effektief sal wees vir die bedekking van vatbare trosdele. Soortgelyke
bedekkings patrone is gevind by die binne trosdele (pedisel en ragis). Dit het egter
betekenisvol verskil van die korrelskil, wat betekenisvol meer spuitbedekking as die binne
trosdele gehad het. ’n Variasie komponent analise het getoon dat die meeste variasie gevind
is tussen korrels en trosse, en heelwat minder vir die beeld analise lesings. Om dieselfde
akkuraatheid te behou, is ten minste 10 trosse per behandeling (1 deel per tros en 3 lesings per
deel) nodig.
Vir die bepaling van biologiese effektiwiteit van verskillende vlakke van
spuitbedekking op B. cinerea voorkoms op druiwe, is druiwe gespuit tydens ertjie- en
trostoemaak-stadia met verskillende volumes van ’n mengsel van fenheksamied en die geel
fluorosensie pigment. Die persentasie fluoresensie pigment is bepaal op die pedisels. Trosse
is vervolgens geinokuleer met droë luggedraagde konidia van B. cinerea in ’n inokulasietoring
en geïnkubeer vir 24 h by hoë relatiewe humiditeit (98%). Die voorkoms van B.
cinerea infeksie op gespuite tros dele is bepaal deur middel van isolasies op paraquat en
Kerssies medium. Liniêre regressies vir trosdeel x stadium kombinasies van persentasie B.
cinerea voorkoms op verskillende trosdele is gepas vir gemiddelde bedekkings waardes. ’n
Verhoging in spuit bedekking het ‘n liniêre vermindering van B. cinerea voorkoms op vatbare
trosdele veroorsaak. Verder is hoër vlakke van B. cinerea op paraquat medium as op Kerssies
medium vir beide die groeistadia gevind. Die kennis wat verkry is uit hierdie studie sal
gebruik word om minimum effektiewe spuitbedekkingsvlakke vir die beheer van B. cinerea
op druiwetrosse te bepaal.
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Epidemiology and control of Pseudocercospora angolensis fruit and leaf spot disease on citrus in ZimbabwePretorius, Mathys Cornelius 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Fruit and Leaf Spot Disease (FLSD) of citrus, caused by Phaeoramularia angolensis, is
found only in 18 countries in Africa, the Comores Islands in the Indian Ocean and Yemen in
the Arabian peninsula. The major citrus export countries in Africa are Morocco, South Africa,
Swaziland, and Zimbabwe. Zimbabwe is the only country affected by FLSD. FLSD is a
disease of major phytosanitary and economic importance and its devastating effect on citrus is
highlighted by the fact that the damage is cosmetic, which renders the fruit unmarketable.
Total crop losses are not uncommon in Kenya. The aims of the present study, therefore, was
was to determine the occurrence of P. angolensis in Zimbabwe and neighbouring
Mozambique, to compare these isolates with the Cercospora Fresen. isolates from Swaziland
and South Africa, to determine the epidemiology of the pathogen and to implement an
effective control strategy to prevent the spread of FLSD.
Leaf samples with citrus canker-like lesions collected in the early 1990’s in Zimbabwe
were found to be infected by the fungus, Phaeoramularia angolensis. Surveys were
undertaken to determine the spread and intensity of FLSD in Zimbabwe and Mozambique. In
Zimbabwe, P. angolensis was limited to an area above the 19° south latitude, predominantly
the moist areas and not the low-lying drier parts of the country. In Mozambique, no P.
angolensis symptoms were found. Observations during the survey indicated that no proper
management systems were implemented by Zimbabwean growers.
A cercosporoid fungus causing a new Fruit and Leaf Spot Disease on Citrus in South
Africa was identified. From morphological and rDNA sequence data (ITS 1, 5.8S and ITS 2),
it was concluded that the new disease was caused by Cercospora penzigii, belonging to the
Cercospora apii species complex. The genera Pseudophaeoramularia and Phaeoramularia
are regarded as synonyms of Pseudocercospora, and subsequently a new combination was
proposed in Pseudocercospora as P. angolensis. Cercospora gigantea was shown to not
represent a species of Cercospora, while Mycosphaerella citri was found to be
morphologically variable, suggesting that it could represent more than one taxon.
A control strategy for the control of FLSD was evaluated in the study. The data showed
that P. angolensis in Zimbabwe can be managed successfully by the removal of all old and neglected orchards, and on timely fungicide applications. Trifloxystrobin + mancozeb +
mineral spray oil (20 g + 200 g + 500 ml/100 l water) applied in November, January and
March was the most effective treatment. Three applications of benomyl + mancozeb +
mineral spray oil (25 g + 200 g + 500 ml/100 l water) applied during the same period, was
the second most effective treatment, and two applications (November and January) of
trifloxystrobin + mineral spray oil (20g + 500 ml/100 l water) and difenoconazole (40 g) per
100 l/water applied twice in November and January, the third most effective treatment.
The spore trap and weather data showed that P. angolensis needs high moisture and
temperatures in excess of 25°C for disease development. It is concluded that P. angolensis in
Zimbabwe can be managed successfully by implementing a holistic approach, which should
be supported by the authorities, organised agriculture and all technical personnel involved in
citrus production. / AFRIKAANSE OPSOMMING: Blaar- en vrugvleksiekte (BVVS) op sitrus, veroorsaak deur Phaeoramularia
angolensis, kom in 18 lande in Afrika voor asook die Comores Eilande in die Indiese Oseaan
en Yemen op die Arabiese skiereiland. Marokko, Suid Afrika, Swaziland en Zimbabwe is
die belangrikste uitvoerders van sitrus in Afrika. Van dié lande het slegs Zimbabwe blaar en
vrugvleksiekte op sitrus. Hierdie siekte is van fitosanitêre en ekonomiese waarde en die
nadelige effek van die siekte, wat slegs kosmetiese van aard is, is venietigend aangesien
vrugte onbemarkbaar is. Totale opbrengsverliese is nie ongewoon in lande soos Kenya nie.
Die doelwitte van die studie was dus om die voorkoms van P. angolensis in Zimbabwe te
bepaal, om die Cercospora Fresen. isolate vanaf Swaziland en Suid-Afrika met mekaar te
vergelyk, om die epidemiologie van die siekte vas te stel en om ‘n effektiewe beheermaatreël
teen die siekte te ondersoek.
Blaarmonsters met kankeragtige letsels wat in die vroeë 1990’s in Zimbabwe gevind
is, het getoon dat die blare geinfekteer is met die swam, Phaeoramularia angolensis.
Ondersoeke is geloots om die verspreiding en intensiteit van BVVS in Zimbabwe en
Mosambiek te bepaal. In Zimbabwe was gevind dat P. angolensis beperk was tot gebiede bo
die 19° Suid breedtegraad, wat die hoër vogtiger gebiede insluit eerder as die droeër,
laagliggende gebiede. Geen P. angolensis simptome kon in Mosambiek gevind word nie.
Tydens die opnames was dit duidelik dat geen geskikte beheerstrategieë toegepas word deur
Zimbabwe se produsente nie.
‘n Nuwe cercosporoid swam, wat blaar en vrugvleksiekte op sitrus is in Suid Afrika
veroorsaak is geidentifiseer. Morfologiese en rDNA volgorde (ITS 1, 5.8S en ITS 2) data het
getoon dat die siekte veroorsaak word deur Cercospora penzigii wat tot die Cercospora apii
spesie kompleks behoort. Die genus Pseudophaeoramularia kan as sinoniem van
Pseudocercospora beskou word en ‘n nuwe kombinasie word voorgestel in
Pseudocercospora as P. angolensis. Cercospora gigantea het getoon dat dit nie ‘n spesie van Cercospora kon verteenwoordig nie terwyl Mycosphaerella citri varieërend voorkom en
meer as een takson kan verteenwoordig.
‘n Beheerstrategie vir die beheer van BVVS is ondersoek. Die data wys dat P. angolensis
in Zimbabwe doeltreffend beheer kan word deur die uitroeiing van ou en verwaarloosde
bome, en deur goed beplande fungisied bespuiting. Trifloxystrobin + mancozeb + minerale
spuitolie (20 g + 200 g + 500 ml/100 l water), wat in November, Januarie en Maart toegedien
is, was die mees effektiefste behandeling. Drie bespuitings van benomyl + mancozeb +
minerale spuitolie (25 g + 200 g + 500 ml/100 l water) wat oor dieselfde tydperk toegedien
is, was die naas beste behandeling. Trifloxystrobin (20 g) + minerale spuitolie (500 ml) per
100 l/water en difenoconazole (40 g) per 100 l/water, beide as twee bespuitings toegedien in
November en Januarie, het die derde beste resultaat opgelewer.
Die spoorlokval en klimatologiese data het getoon dat P. angolensis vogtige toestande en
temperature hoër as 25°C benodig vir siekteontwikkeling. Die afleiding uit die studie is dat
P. angolensis suksesvol beheer kan word indien ‘n holistiese benadering gevolg word en alle
rolspelers naamlik die owerheid, georganiseerde landbou en tegniese personeel die proses
ondersteun.
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The characterization and control of Phomopsis cane and leaf spot on vineMostert, Lizel 12 1900 (has links)
Thesis (MScAgric.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Phomopsis cane and leaf spot disease of grapevine is an economically important disease
in many of the vine-growing areas of the world. Four different Phomopsis spp. have
previously been associated with this disease. The present study investigates the
taxonomic significance of the different taxa found on grapevines in South Africa, as well
as the endophytic growth and fungicide sensitivity of Phomopsis viticola isolates. The
thesis is compiled of several different parts, which deal with specific, but related topics,
and hence some duplication has been unavoidable.
Understanding the epidemiology of a disease is important for the correct timing of
disease control. To investigate the endophytic growth of P. viticola, asymptomatic
shoots were collected at eight different growth stages. Nodes, internodes, leaf petioles,
leaves, tendrils and bunch peduncles were investigated. Two Phomopsis spp., taxon 1 and
2 were identified in this study. The Phomopsis viticola-complex had a relative
importance of 9% and accounted for 3% of the isolations. P. viticola (taxon 2) is mainly
isolated from the nodes and internodes. Inoculations of healthy, young vine tissue
confirmed taxon 2 to be a virulent pathogen, suggesting that it is a latent pathogen rather
than an endophyte. In contrast, taxon 1 appeared to be a true endophyte, and did not
seem to be an important pathogen on vines.
The true identity of the causal organism of Phomopsis cane and leaf spot disease
was investigated by collecting samples from 58 different vineyards in the grapevine
growing areas of the Western Cape. P. viiicola occurred in grapevine material collected
from Lutzville to Swellendam, but was not found in the Oudtshoorn and Orange River
grapevine areas. Diaporthe perjuncta (taxon 1), P. vutcola (taxon 2), taxon 3 and a
Phomopsis species commonly associated with shoot blight of peaches in the U.S.A., P.
amygdali, were identified among the South African grapevine isolates. Examination of
the Australian culture designated as taxon 4 found it to be a species of Libertella, thus
excluding it from the P. viticola-complex. An Italian isolate was found to represent a
species of Phomopsis not previously known from grapevines, and this was subsequently
described as taxon 5. Species delimitation was based on morphological and cultural
characteristics, stem inoculations and the formation of the teleomorph in vitro. The
identity of each morphological taxon was confirmed by means of phylogenetic analyses
of the nuclear ribosomal DNA internal transcribed spacers (ITS 1 and ITS2) and the 5'
end partial sequence of the mitochondrial small subunit (mtSSU). P. amygdali,
associated with peach shoot blight in the U.S.A., was isolated once only and appeared to
be of lesser importance in this disease complex. Furthermore, taxa 1 (Diaporthe
perjuncta) and 3 were also rarely encountered and proved to be non-pathogenic,
indicating their non-functional role in Phomopsis cane and leaf spot disease. Taxon 2
(Phomopsis viticolas was common and widely distributed in diseased vineyards. This
taxon was associated with the typical disease symptoms and proved to be pathogenic.
Morphologically taxon 2 corresponded best with P. viticola, which was also neotypified
in this study. Taxon 2 was mostly isolated from buds and nodes, indicating that these are
important sites in which the fungus survives during winter. Molecular data indicated that
taxon 3 and P. amygdali were not host specific to grapevine.
The currently used foliar fungicides were compared to the new strobilurin
fungicides. The effects of nine fungicides (azoxystrobin, flusilazole, folpet, fosetyl-
Al+mancozeb, kresoxim-methyl, mancozeb, penconazole, spiroxamine and
trifloxystrobin) were tested in vitro on inhibition of mycelial growth. The following EC50
(ug/ml) values were obtained: azoxystrobin (0.350), flusilazole (0.007), folpet (4.489),
fosetyl-Al+mancozeb (3.925), kresoxim-methyl (1.665), mancozeb (2.891), penconazole
(0.023), spiroxamine (0.321) and trifloxystrobin (0.051). Additionally, azoxystrobin,
folpet, kresoxim-methyl, mancozeb, propineb and trifloxystrobin were tested for their
ability to inhibit spore germination in vitro. The subsequent EC50 (ug/ml) values were
obtained: azoxystrobin 0.123), folpet (0.510), kresoxim-methyl (0.0037), mancozeb
(0.250), propineb (0.156) and trifloxystrobin (0.003). The results reported in part 4
showed that the strobilurin fungicides inhibited the mycelial growth and spore
germination of P. viticola. However, further trials need to be conducted to verify these
findings under field conditions. In the present study taxa 1, 3 and P. amygdali were
infrequently isolated, suggesting that they played a less prominent role in the P. viticolacomplex. / AFRIKAANSE OPSOMMING: Streepvleksiekte van wingerd is 'n ekonomies belangrike siekte wat in die meeste
wingerdproduserende gebiede van die wêreld voorkom. Vier Phomopsis spesies is in die
verlede met dié siekte geassosieer. Hierdie studie ondersoek die taksonomiese
belangrikheid van die verskillende taksa wat op wingerd in Suid Afrika gevind word,
asook die endofietiese groei en fungisiedsensitiwiteit van die Phomopsis vitico/a isolate.
Hierdie tesis bestaan uit verskeie dele met spesifieke, maar verwante onderwerpe wat tot
onafwendbare duplisering lei.
Dit is belangrik om die epidemiologie van 'n siekte te verstaan sodat korrekte en
tydsberekende siektebeheer toegepas kan word. Die endofietiese groei van P. vitico/a is
ondersoek deur simptoomlose lote by agt verskillende groei stadiums te versamel.
Nodusse, internodusse, blaarstele, blare, rankies en trosstele is ondersoek. Twee
Phomopsis spp., takson 1 en 2 is geïdentifiseer. Die Phomopsis vitico/a-kompleks het
3% van die isolasies uitgemaak en 'n relatiewe belangrikheid van 9% getoon. P. vitico/a
(takson 2) is meestal uit die nodus en internodus geïsoleer. lnokulasies van gesonde, jong
wingerdweefsel het bevestig dat takson 2 'n virulente patogeen is en dat die takson eerder
'n latente patogeen as 'n endofiet is. In teenstelling hiermee is takson 1 'n ware endofiet
en 'n onbelangrike patogeen op wingerd.
Die ware identiteit van die veroorsakende organisme van streepvlek is ondersoek
deur plantmateriaal vanaf 58 verskillende wingerde in die wingerproduserende gebiede
van die Wes-Kaap te versamel. P. vitico/a is in wingerdmateriaal vanaf Lutzville tot
Swellendam aangetref, maar nie in die Oudtshoorn en Oranjerivier wingerd produserende
gebiede nie. Diaporthe perjuncta (takson 1), P. vitico/a (takson 2), takson 3 en P.
amygdali is in die Suid Afrikaanse wingerdisolate geïdentifiseer. P. amygdali word met
lootverskroeiing van perske bome in die V.S.A. geassosieer. Die Australiese isolaat wat
benoem is as takson 4, is met die huidige ondersoek gevind om 'n spesie van Libertella
te wees. Takson 4 is daarvolgens uit die P. vitico/a-kompleks gelaat. 'n Italiaanse isolaat
het 'n nuwe spesie van Phomopsis op wingerd verteenwoordig en is vervolgens as takson
5 beskryf. Spesie-onderskeiding is op morfologiese en kulturele eienskappe,
staminokulasies en die vorming van die teleomorf in vitro gebaseer. Die identiteit vanelke morfologiese takson is met behulp van filogenetiese analises van die nukleêre
ribosomale DNS intern transkriberende spasieerders (ITS 1 en ITS2) en die 5' punt
gedeeltelike nukleotied volgorde van die mitochondriale klein subeenheid (mtSSU)
bevestig. P. amygdali is slegs een keer geïsoleer en blyk van minder belang in die
siektekompleks te wees. Takson 1 (Diaporthe perjuneta) en takson 3 het ook min
voorgekom en is nie-patogenies, wat hul nie-funksionele rol in streepvleksiekte aandui.
Takson 2 (P. viticola) is algemeen geïsoleer en kom wyd verspreid voor. Hierdie takson
is geassosieer met die tipiese siektesimptome en is ook patogenies. Morfologies stem
takson 2 met P. viiicola ooreen en is ook geneotipifiseer in hierdie studie. Takson 2 is
meestal vanaf die ogies en nodusse geïsoleer, wat daarop dui dat hierdie belangrike setels
is waar die swam tydens die winter oorleef. Die molekulêre data toon aan dat takson 3 en
P. amygdali nie gasheerspesifiek tot wingerd is nie.
Die swamdoders wat tans teen streepvlek gebruik word, is met die nuwe
strobilurin swamdoders vergelyk. Die effek van nege swamdoders (azoksistrobin,
flusilasool, folpet, fosetyl-Al + mancozeb, kresoxirn-metiel, mankozeb, penconasool,
spiroksamien en trifloksistrobin) is in vitro op die inhibisie van miseliumgroei getoets.
Die volgende EKso-waardes (g/ml) is verkry: azoxystrobin (0.350), flusilasool (0.007),
folpet (4.489), fosetiel-Al + mankozeb (3.925), kresoxirn-metiel (l.665), mankozeb
(2.891), penkonasool (0.023), spiroksamien (0.321) en trifloxystrobin (0.051).
Azoxystrobin, folpet, kresoxim-rnetiel, mankozeb, propineb en trifloksistrobin is ook in
vitro getoets vir hul inhibisie op spoorontkieming. Die volgende EKso-waardes is verkry:
azoxystrobin (0.123), folpet (0.510), kresoxim-metiel (0.0037), mankozeb (0.250),
propineb (0.156) en trifloxystrobin (0.003). Die resultate vervat in deel 4 toon dat die
strobilurin swamdoders die miseliumgroei en spoorontkieming van P. viticola inhibeer.
Toetsing in die veld word egter benodig om die effektiwiteit van die middels te bevestig.
In hierdie studie is taksa I, 3 en P. amygdali selde geïsoleer, wat aangedui het dat hierdie
taksa 'n minder belangrike rol in die P. viticola-kompleks speel.
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The detection of cherry leaf-roll nepovirus and the use of molecular markers for germplasm identification in walnuts (Juglans regia L.)Mkhize, Thokozani M 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The aim of this study was to combine two common diagnostic tools:
serological kits and genetic fingerprinting to identify cherry leaf-roll nepovirus
(CLRV), and to establish a marker system to characterize walnut germplasm.
The detection of plant viruses is difficult. Restrictions are imposed for
quarantine purposes on the importation of plant material from foreign
countries. Modern techniques such as a PCR based screening method for
CLRV are required to ensure material do not harbour viruses. A primer pair
was designed to amplify a 430 bp non-coding homologous region. For the
choice of primers, consensus sequences were considered and areas where
the sequence data shared 98.5% homology, were chosen. The sensitivity of
this detection method was 100-fold higher when compared to the ELISA. The
PCR fragment was verified by nucleotide sequencing.
AFLP technology was used to identify polymorphic fragments for 6 walnut
cultivars and a rootstock, and SCARs were developed from AFLP specific
bands. The AFLP technique distinguished all the walnut cultivars and the
rootstock. However, conversion of AFLP fragments to SCAR markers for the
development of a simple robust technique for cultivar discrimination, was not
successful. Using 27 AFLP primer combinations, polymorphic fragments as
high as 47.8% were scored. The reason for the lack of efficient conversion
was as the result of the AFLP technique. The SCAR primers were generated
from sequences internal to the AFLP primers but the specificity of the markers
was in the AFLP primers not the internal sequence.
In this study using AFLP, walnut cultivars were found to be closely related.
The AFLP primer pairs used, provided polymorphic fragments. From these
fragments, 7 SCAR markers were developed. It was expected that these
SCARs derived from the AFLP markers would detect slight differences
between cultivars. The Paradox SCAR marker was the only one that could
divide the cultivars into two groups. When Chandler SCAR products were
digested with the restriction enzyme Rsal, the same banding pattern as that of
Paradox SCAR products was observed. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om twee algemene opsporingstegnieke te
kombineer: serologiese toetsstelle en genetiese vingerafdrukke om cherry
leaf-roll nepovirus (CLRV) te eien en om In merkersisteem te ontwikkel wat
okkerneut kiemplasma kan karakteriseer.
Die opsporing van plant virusse is baie moeilik. As gevolg van kwarantyn
vereistes, word daar beperkinge geplaas word op die invoer van plant
materiaal vanuit die buiteland. Moderne tegnieke soos hierdie een wat op
PKR berus, word benodig om te verseker dat CLRV nie in plantmateriaal
teenwoordig is nie. In Stel inleiers is ontwerp wat In 430 bp nie-koderende
homoloë area amplifiseer. Hiervoor is konsensus volgordes bestudeer en
slegs die volgordes wat 98,5% homologie getoon het, is gekies. In
vergelyking met ELISA was die sensitiwiteit van hierdie deteksie metode 100
maal beter. DNA volgordebepaling is op die resulterende fragment gedoen
om die PKR produk te verifieer.
AFLP tegnologie is gebruik om polimorfiese fraqmente vir 6 okkerneut
kultivars en 'n onderstok te identifiseer en SCARs is uit hierdie fragmente
ontwikkel. Die AFLP tegniek kon tussen al die okkerneut kultivars en die
onderstok onderskei. Die omskakeling van die AFLP fragmente in SCAR
merkers om sodoende In eenvoudige kragtige tegniek vir kultivar
onderskeiding te ontwikkel, was egter nie suksesvol nie. Met die gebruik van
27 AFLP inleier kombinasies, kon polimorfiese fragmente van so hoog as
47.8% verkry word. Die rede hoekom omskakeling onsuksesvol was lê by die aard van die AFLP tegniek. Die SCAR inleiers is ontwikkel uit volyordes
intern tot die AFLP inleiers, maar die spesifisiteit van die merkers het juis in
die AFLP inleiers gelê en nie in die interne volgordes nie.
In hierdie studie, met die gebruik van AFLP, is gevind dat okkerneut kultivars
baie naby verwant is. Die AFLP inleierstelle wat gebruik is, het polimorfiese
fragmente gelewer. Uit hierdie fragmente is 7 SCAR merkers ontwikkel. Daar
is verwag dat die SCARs wat uit die AFLP merkers ontwikkel is, klein verskille
tussen kultivars sou opspoor. Dit was egter net die Paradox SCAR merker
wat die kultivars in twee groepe kon verdeel. Restriksie ensiem vertering met
Rsalop die Chandler SCAR produkte het dieselfde bandpatrone as die van
die Paradox SCAR produkte gelewer.
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Overexpression and evaluation of an antimicrobial peptide from Heuchera sanguinea (Hs-AFP1) for inhibition of fungal pathogens in transgenic tabaccoDe Beer, Abre 04 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Seed germination is the most vulnerable time in a plant's life cycle, since the thick protective
seed coat ruptures and the moist and humid soil environment not only favours seed
germination, but also the growth and development of plant pathogens. Infection of plant seeds
during germination, however, is the exception rather than the rule. Plant seeds have
- - -developed a--cemplex preformed defense mechanism that includes anttfungal agents thatdiffuse
into the surrounding environment to form a protective layer around the seed. This
protective layer prevents fungal and bacterial pathogens from infecting the young seedling.
Over the last decade, scientists have studied the defense mechanisms of different
seeds in an effort to understand and ultimately to introduce and/or manipulate these
mechanisms in plants as part of the plant's endogenous disease resistance to pathogens.
Various chemical compounds, peptides and proteins that showed strong in vitro activities
against various fungi were isolated in these efforts. The mere demonstration of in vitro activity
alone, however, is not sufficient to assign a defense role to these antifungal agents. Typically,
mutant plants that have lost the ability to produce the antifungal agent, or mutants that are
overproducing the agent, have been used to correlate the mutant phenotype to either a
decline or increase in disease resistance respectively. Genetic transformation and the
subsequent development of transgenic plants have made an unprecedented impact in this
regard, specifically in understanding the role of specific defense-related proteins and their
interaction with plant pathogens.
In this study, the antifungal peptide, Hs-AFP1, from Heuchera sanguinea, a plant
defensin, was evaluated in a heterologous in planta environment as a defense protein with
potential for engineering disease resistant crops. The in vitro assays performed with Hs-AFP1
against Botrytis cinerea showed antifungal activities of 88% growth inhibition at a
concentration of 8 J,lg/ml of the purified peptide, while inducing a characteristic
hyperbranching effect on the Botrytis hyphae. Tobacco was subsequently transformed with a
construct, pFAJ3068, expressing Hs-AFP1 under the strong constitutive 35S promoter. The
peptide was targeted to the apoplastic region with the signal peptide from Mj-AMP2, an
antimicrobial peptide from Mirabilis jalapa. Due to reports of peptide instability in transgenic
plant systems, two additional constructs were prepared and transformed into tobacco to
anticipate possible Hs-AFP1 instability in the heterologous tobacco environment. A putative
peptide stabilization construct, pHs-EXG1, consisted of a fusion between Hs-AFP1 and the
antifungal exo-glucanase (encoded by EXG1) from Saccharomyces cerevisiae. A control
construct, pMj-EXG1, expressing EXG1 targeted to the apoplastic region with the Mj-AMP2
signal peptide, was also prepared and transformed into tobacco to normalize the background
antifungal activity as a result of the exoglucanase in the fusion construct lines. Tobacco was successfully transformed with pFAJ3068, pHs-EXG1 and pMj-EXG1,
resulting in transgenic tobacco lines designated THs, THE and TME respectively. Transgene
expression was confirmed for the THs and THE transgenic lines. The translation of these
transcripts into proteins was also confirmed with Western blot analysis. Moreover, the
heterologous production of Hs-AFP1 in tobacco led to an increase in disease resistance to
B. cinerea in the THs lines in comparison with the untransformed tobacco controls. An
increase of up to 42% in disease resistance was observed in an in planta detached leaf
assay. Crude protein extracts from the THs lines were also analyzed in an in vitro quantitative
fungal growth assay. This assay confirmed the results obtained with the disease resistance
assay, with crude protein extracts exhibiting up to 40% fungal growth inhibition. The
incubation of B. cinerea in the presence of crude protein extracts from THs lines resulted in
hyperbranching of the fungal hyphae, which is characteristic of Hs-AFP1 activity.
From these analyses it was clear that the heterologously expressed Hs-AFP1 was
quite stable in the transgenic environment. The fusion between Hs-AFP1 and EXG1 did not
increase the stability of Hs-AFP1, but rather led to a loss of the Hs-AFP1 activity. All the
analyses performed showed the THE lines to be reduced in their ability to inhibit fungal
infection in comparison to the THs line. Also, microscopic analysis of the effects of the crude
THE extracts on B. cinerea growth showed no hyperbranching activity, again confirming the
loss of peptide activity due to the fusion to EXG1. This is in agreement with previous work, in
which sarcotoxin 1A was fused to a reporter gene and also lost activity.
Although integration of the Mj-EXG1 expression cassette was confirmed, no mRNA
levels could be detected with Northern blot or RT-PCR analysis of the TME lines. These lines
also did not show any in vitro antifungal activities, probably indicating post-transcriptional
gene silencing. This silencing was overcome in the fusion constructs that were expressed in
the THE plant lines. These lines also showed EXG1 protein activity, as measured by
~-glucosidase assays. Although the THE lines did not serve the functions originally
envisaged, they fortuitously showed that a fusion strategy might stabilize glucanase
expression in a transgenic environment. A variety of glucanases have been shown to be
prone to gene silencing when overexpressed in a plant environment and the yeast glucanase
can now be added to that list if it is not present as a fusion protein.
Overall, this study confirmed that Hs-AFP1 is involved in plant defense systems and
provided valuable information on the stability of small peptides in a heterologous environment.
The positive results obtained with overexpressed Hs-AFP1 on fungal inhibition in this study
merits further investigations into the use of this peptide in the engineering of disease-resistant
crops. / AFRIKAANSE OPSOMMING: Saadontkieming is die mees vatbare tyd vir siekteontwikkeling gedurende 'n plant se
lewenssiklus. Die saadhuid bars en die vogtige grondkondisies bevoordeel nie net
saadontkieming nie, maar ook die groei en ontwikkeling van plantpatogene. Infeksie van
plantsade tydens ontkieming is egter die uitsondering eerder as die reël. Plantsade besit
komplekse -veraeaigingsfueganfsmes-reen moontlike - patoqeeninteksies. Die meqanismes
sluit die produksie van antifungiese agense, wat tydens saadontkieming na die omliggende
omgewing diffundeer om 'n beskermende sone om die ontkiemende saad te vorm, in. Die
gevolglike antifungiese sone beskerm die saad teen infeksie deur bakterieë en swamme.
Gedurende die laaste dekade het navorsers baie aandag aan die bestudering van
plantsaadverdedigingsmeganismes gegee. Dié kennis word gebruik om die verdedigingsmeganismes
beter te verstaan, asook om dié meganismes te manipuleer en/of oor te dra aan
plantspesies met inherente swak weerstandsmeganismes wat gereeld aan
plantpatogeeninfeksies onderhewig is. Navorsing op plantsade het tot die isolasie van
verskeie chemiese agense, peptiede en proteïene, wat sterk in vitro aktiwiteite teen 'n wye
reeks swampatogene vertoon, gelei. Die vermoë van dié agense om swamme in 'n in vitro
omgewing te inhibeer, is alleen egter nie 'n bewys dat hulle 'n rol in plantverdeging speel nie.
Studies waar mutante gebruik word, is gewens om addisionele bewys te lewer dat die
substanse 'n rol in plantverdediging vervul. Sodanige mutante sluit plantlyne, waarin die geen
van belang gemuteer is of ooruitgedruk word om so die rol van die geen in 'n in planta
omgewing te bepaal in. In hierdie toepassings het genetiese transformasie en die daarstelling
van transgeniese plante 'n ongeëwenaarde bydrae gelewer.
In dié studie is die antifungiese peptied, Hs-AFP1, wat aan die peptiedgroep van plant-
"defensins" behoort en van Heuchera sanguine a afkomstig is, in 'n heteroloë in planta
omgewing geëvalueer as 'n verdedigingspeptied met die potensiaal om in die generering van
transgeniese siektebestande gewasse gebruik te word. Die antifungiese aktiwiteit van
Hs-AFP1 is teen Botrytis cinerea in 'n in vitro reaksie geëvalueer, waar die toediening van
8 ,",g/mlgesuiwerde Hs-AFP1 peptied aanleiding gegee het tot 'n 88% afname in hifegroei van
B. cinerea. Hipervertakkings van swamhifes, 'n kenmerkende eienskap van Hs-AFP1
aktiwiteit, kon duidelik waargeneem word. Tabakplante is voorts getransformeer met 'n
konstruk, pFAJ3068, wat die koderende geen van Hs-AFP1 onder die sterk konstitutiewe
CaMV 35S promotor bevat het. Die peptied is met behulp van die seinpeptied wat afkomstig
is van die Mirabilis jalapa antimikrobiese peptied, Mj-AMP2, na die apoplastiese omgewing
geteiken. Voorheen is gerapporteer dat transgeniese peptiede in die heteroloë omgewing
soms onstabiel is. Dit het gelei tot die generering van twee addisionele konstrukte om die
moontlikheid van peptiedonstabiliteit te ondervang. 'n Stabiliseringskonstruk, pHs-EXG1, bestaande uit In versmelting tussen Hs-AFP1 en In antifungiese eksoglukanase van
Saccharomyces cerevisiae, gekodeer deur EXG1, is in tabakplante getransformeer. In
Kontrolekonstruk, pMj-EXG1, met die EXG1-geen saam met die Mj-AMP2-seinpeptied, is ook
voorberei en in tabakplante getransformeer. Dit is gebruik om die antifungiese aktiwiteit van
die eksoglukanase in die antifungiese aktiwiteitstoetse van die stabiliseringskonstruk te
kwantifiseer en te normaliseer.
Tabak is suksesvol met pFAJ3068, pHs-EXG1 en pMj-EXG1 getransformeer, wat
onderskeidelik gelei het tot die sogenaamde THs, THE en TME transgeniese tabaklyne.
Transgeentranskripsie en -translasie in die THs en THE tabaklyne is onderskeidelik deur
Noordelike- en Westelike-kladanalises bevestig. Die aktiewe uitdrukking van Hs-AFP1 het die
vermoë van tabakplante om B. cinerea infeksies te weerstaan, met tot 42% verhoog in
vergelyking met ongetransformeerde kontrole tabakplante tydens 'n in planta
siekteweerstandstoets. Totale proteïenekstrakte van THs tabaklyne is voorts ook in In in vitro
inhibisietoets geëvalueer, wat gelei het tot resultate wat goed met dié van die in planta toetse
ooreenstem. Die totale proteïenekstrakte het swamgroei met 40% geïnhibeer en die
kenmerkende hipervertakking van Hs-AFP1-aktiwiteit is ook mikroskopies waargeneem.
Resultate wat verkry is vanaf al die analises wat op die transgeniese THs tabaklyne
uitgevoer is, het aangedui dat Hs-AFP1 baie stabiel in die heteroloë tabakomgewing is en
peptiedstabiliteit was dus nie In probleem, soos verwag is nie. Die fusie tussen Hs-AFP1 en
EXG1 het dus nie die stabiliteit van die reeds stabiele Hs-AFP1 peptied verder verbeter nie,
maar het wel tot die verlies van Hs-AFP1 aktiwiteit gelei. Die antifungiese analises van die
THE tabaklyne het verder bevestig dat dié lyne selfs swakker inhibisie van B. cinereainfeksies
tot gevolg gehad het, as ongetransformeerde tabakplante. Mikroskopiese analises
van totale THE proteïenekstrakte het voorts ook geen kenmerkende hipervertakkings in die
swamhifes vertoon nie, wat alles daarop dui dat die Hs-AFP1-deel van die fusieproteïen as
gevolg van die fusie met EXG1 geïnaktiveer is. Dié resultaat is in lyn met vorige navorsing,
wat getoon het dat In ander peptied, sarcotoxin 1A, sy antifungiese aktiwiteit verloor indien dit
met In verklikkergeen versmelt word.
Alhoewel integrasie van die pMj-EXG1-konstruk in die TME-tabaklyne bevestig is, kon
geen mRNA met Noordelike-klad- of trutranskriptase-PKR (RT-PKR)-analises waargeneem
word nie. Die TME plant het ook geen antifungiese aktiwiteit in in vitro toetse getoon nie en dit
het geblyk dat die pMj-EXG1-konstruk aan geenafskakeling in die heteroloë tabakomgewing
onderworpe was. Dié afskakelingseffek is egter in die THE plante oorkom, aangesien
laasgenoemde sterk EXG1 proteïenaktiwiteit met J3-glukosidase aktiwiteitstoetse vertoon het.
Alhoewel die THE plante nie die stabiliteit van Hs-AFP1 verbeter het nie, het dit onwerwags
tot die stabilisering van EXG1 in In heteroloë omgewing gelei. Versmeltingstegnologie kan
dus moontlik gebruik word as 'n strategie om ander glukanases, wat bekend is vir
geenafskakeling in transgeniese omgewings, heteroloog uit te druk. In die geheel gesien, het dié studie getoon dat Hs-AFP1 'n onbetwiste rol in
plantverdedigingsmeganismes speel en daar is voorts ook meer kennis oor die stabiliteit van
peptiede in 'n heteraloë plantomgewing ingewin. Die positiewe resultate t.o.v. die verhoogde
siekteweerstand in die transgeniese THs plantlyne regverdig ook die verdere bestudering van
dié peptied om transgeniese siekteweerstand in gewasse te bewerkstellig.
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Modifying an artificial diet for mass rearing mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), using locally available maize mealRini, Lulama Angela 03 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann) (Diptera:
Tephritidae) is well-known as a destructive pest of fruit worldwide. Various control
methods have been used against this insect. The sterile insect technique (SIT) is used
as an important and successful technological method for controlling or eradicating
this pest in many countries. A key factor to successfully apply SIT is dependent on the
availability of efficient and economical rearing methods.
Artificial insect diets with low cost bulking agents have been of interest to many
researchers. The present study investigated the use of locally available maize meal as
a bulking agent in such diets. Maize meal is used for human consumption (in South
Africa) and contains small amounts of protein. This makes the reduction of imported
torula yeast as an ingredient of the diet and source of protein possible, thereby
reducing the cost of the diet.
The larval development of the Medfly reared on artificial diets was studied in
small and large-scale tests. The effect of the diets on larval production was evaluated
using pupal recovery, pupal weight, flight ability, sex ratio, fecundity and egg
fertility.
The results of the small-scale tests showed that the diet containing maize meal
could be used to produce Medfly more economically than the standard Krige diet used
by the ARC Infruitec-Nietvoorbij Research Institute at Stellenbosch. However, in
large-scale tests the ingredients quantities of the diets used were not the same as those
of small scale-tests. The cost of the modified larval diet was not reduced in large-scale
tests. This was ascribed to the number of eggs used in the tests to produce one million of fruit flies. The maize meal with reduced number of eggs require more diet to
produce one million flies therefore, making it more expensive and less viable. When
similar amounts of eggs were used, the diet appears to be a suitable alternative as the
result obtained was almost similar to those of the Krige diet. / AFRIKAANSE OPSOMMING: Die Mediterreens vrugtevlieg ("Medfly"), Ceratitis capitata (Wiedemann)
(Diptera: Tephritidae) is wêreldwyd 'n skadelike plaag. Die steriele insek tegniek
(SIT) het in baie lande 'n belangrike en suksesvolle manier geword om die plaag te
beheer en uit te roei. Die belangrikste voorvereiste vir die suksesvolle toepassing van
SIT is die beskikbaarheid van doeltreffende en ekonomiese teelmetodes.
Meeste navorsers is geïntereseerd in kunsmatige diëte met 'n goedkoop
vulstof. Hierdie studie is ontwerp om die gebruik van plaaslik beskikbare mieliemeel
as vulstof te ondersoek. In Suid-Afrika word dit vir menslike gebruik aangewend en
bevat klein hoeveelhede proteïene wat 'n vermindering van die ingevoerde torula gis
moontlik kan maak, en sodoende die koste van die dieët kan verminder.
Die ontwikkeling van Medfly larwes op kunsmatige diëte is bestudeer In
kleinskaalse en grootskaalse eksperimente. Die invloed van die diëte op larwale
produksie is evalueer deur gebruik te maak van van papie-ontwikkeling, papie-gewig,
vliegvermoë, geslagsverhouding, volwasse voortplantingsvermoë en
eiervrugbaarheid.
Die resultate van die kleinskaalse toetse het aangetoon dat die mieliemeel
dieët gebruik kan word om Medfly meer ekonomies as met die standaard Krige dieët,
wat in die ARC Infruitec-Nietvoorbij navorsings instituut by Stellenbosch gebruik
word, te teel. By die grootskaalse toetse was die koste nie laer nie. Dit word
toegeskryf aan die aantal eiers wat gebruik is om 'n miljoen vlieë te produseer. Die
mieliemeel dieët met 'n verminderde aantal eiers benodig meer dieët om 'n miljoen
vlieë te produseer, wat dit duurder en minder lewensvatbaar maak. Wanneer
soortgelyke hoeveelhede eiers gebruik was, het dit geblyk dat die dieët 'n opsie is,
want die resultaat was soortgelyk aan dié van die Krige dieët.
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EFFECTS OF SOIL SOLARIZATION AND ANTAGONISTIC BACTERIA ON MACROPHOMINA PHASEOLINA AND SCLEROTIUM ROLFSII (ARIZONA).MIHAIL, JEANNE DENYSE. January 1983 (has links)
An evaluation was made of soil solarization to control Macrophomina phaseolina and Sclerotium rolfsii under the climatic conditions of the Sonoran Desert region of Arizona. Tarping of moist soil with clear polyethylene in the summer was most effective in raising soil temperatures, while tarping during the fall and spring were less efficient. In one summer trial, the maximum temperatures achieved were 7-8 C higher than control plots at 1, 15, and 30 cm depths. In none of the tests was the application of tarp effective in reducing M. phaseolina populations to non-detectable levels. After a six-week summer solarization treatment, S. rolfsii was controlled at the 15-cm but not the 30-cm depth. During a fall treatment control of S. rolfsii was achieved only at the 1-cm depth. After solarization, seeds of Euphorbia lathyris were planted in solarized and control plots. The incidence of M. phaseolina-associated mortality among seedlings planted in solarized plots was always the same as the control plot with the highest disease incidence. The utility of this technique may be limited by the heat tolerance of the target organisms. Studies of bacterial antagonists were initiated to determine their utility in enhancing pathogen control after the solarization treatment. Screening 43 bacterial isolates showed that seven of Pseudomonas fluorescens and one of Serratia marcescens exhibited some form of antagonism toward M. phaseolina, S. rolfsii and Verticillium dahliae in vitro. Antagonism was manifested as a complete inhibition of fungal development or reduced hyphal development coupled with suppression of sclerotial development. The action of the antagonists was found to be fungitoxic or fungistatic rather than fungicidal. None of the four P. fluorescens isolates tested were effective in preventing M. phaseolina infection of E. lathyris seedlings. The ability of these bacteria to prevent sclerotial formation while still permitting hyphal growth may be a useful technique for studying the two phases of the fungal life cycle separately.
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Optimisation of fungicide spray coverage on grapevine and the incidence of Botrytis cinereaBrink, Johannes Cornelius (Jan-Cor) 03 1900 (has links)
Thesis (PhD(Agric))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Despite adherence to fungicide spray schedules and label recommendations, table
and wine grape producers invariably suffer crop losses when environmental conditions
are conducive to fruit and foliar pathogens. Registered fungicides are effective and poor
control is often attributed to: 1) improper spray timing, 2) reduced sensitivity to
fungicides in the pathogen populations, and 3) poor spray deposition. Spray timing,
management of fungicide resistance and the epidemiology of Botrytis cinerea have been
thoroughly researched under South African conditions on grape crops. However, limited
research regarding spray deposition exists in South Africa, probably due to a lack of
proper spray deposition assessment protocols.
To determine minimum spray deposition quantity and quality levels needed for
effective B. cinerea control, bunches and leaves of table (Waltham Cross) and wine
grapes (Chenin blanc) were sprayed at various stages using different volumes with a
precision spray gun. A deposition assessment protocol using fluorometry,
photomicrography and digital image analyses was improved. Deposition values correlated
favourably with Botrytis infection. Increasing spray volume increased spray deposition;
however, at a certain point, deposition quality remained constant and B. cinerea
infections did not decrease significantly with increasing spray volume, indicating the
importance of both spray deposition quantity and quality. Fluorescent pigment area that
effected 75% control of B. cinerea infection (FPC75 values) was calculated for leaves,
pedicels and receptacles at different growth stages. The FPC75 values obtained in this
study can be used as benchmarks to evaluate future spray application.
In order to study the optimisation of spray deposition with existing application
technology (air blast and air shear sprayers) in commercial vineyards, spray deposition
quantity and quality values were assessed from leaves and structural bunch parts of wine
(Chenin blanc) and table grapes (Waltham Cross) and compared with FPC75 values.
Spray trials were conducted at different growth stages at current best-practice
recommendations, and with a range of spray volumes but with spray mixture
concentration amended accordingly (i.e. fixed dosage per hectare). Spray trails indicated that deposition levels following current best-practice spray application were sub-optimal
to control B. cinerea infections on bunches and leaves.
Deposition values between air blast and air shear sprayers were generally similar.
The air blast sprayer resulted in higher deposition levels with diluted spraying and
increased spray volume; however, when dosage per hectare was kept constant, no
significant differences were calculated between spray volumes (250-1000 L/ha),
indicating that this sprayer can as effectively but more efficiently be used at lower spray
volume. The air shear were not as efficient at higher spray volumes (>500 L/ha), but was
superior at low volume concentrate application (≈250 L/ha at 4× concentration). This
study clearly demonstrated the efficacy and cost-saving potential in optimising spray
application with respect to application technology. / AFRIKAANSE OPSOMMING: Wingerdprodusente kan oesverliese ondervind indien omgewingstoestande
bevorderlik is vir swampatogene. Siektes word onvoldoende beheer ten spyte van die
nakoming van korrekte swamdoder aanbevelings. Geregistreerde swamdoders is
effektief, mits die vatbare plantdele voldoende spuitbedekking ontvang. Onvoldoende
siekte beheer kan gewoonlik toegeskryf word aan: 1) verkeerde spuit tydsberekening, 2)
vermindere sensitiwiteit in patogeen-populasies teen swamdoders, en 3) swak
spuitbedekking. Spuit tydsberekening, die bestuur van weerstand teen swamdoders en die
epidemiologie van Botrytis cinerea is deeglik onder Suid-Afrikaanse toestande nagevors.
Nietemin is daar beperkte navorsing oor spuitbedekking, waarskynlik weens 'n gebrek aan
behoorlike spuitbedekking assesseringsprotokol.
Om te bepaal hoeveel spuitbedekking (% area bedek deur fluoresserende pigment)
nodig is om 75% van B. cinerea infeksies (FPC75 waardes) op vatbare wingerddele te
beheer, is druiwetrosse en blare van tafel- en wyndruiwe (Waltham Cross en Chenin
blanc, onderskeidelik) op verskillende groei stadiums en spuitvolumes in die laboratorium
gespuit. ‘n Assesseringsprotokol van spuitbedekking op vatbare druifdele en blare is
ontwikkel deur gebruik te maak van fluorometrie, fotomikrografie en digitale
beeldanalise. Spuitbedekking het goed met Botrytis infeksies gekorreleer. Toenemende
spuitvolume het bedekking laat toeneem, maar egter net tot 'n sekere punt, waar die
kwantiteit van die bedekking nog toegeneem het, maar die kwaliteit van bedekking en B. cinerea infeksies nie beduidend toegeneem het nie. Dit is ‘n aanduiding van die
belangrikheid van beide die kwantiteit en kwaliteit van spuitbedekking. Die FPC75
waardes wat in hierdie studie verkry is, kan as drempelwaardes om toekomstige
spuittoediening te evalueer, gebruik word.
Ten einde spuitbedekking met bestaande tegnologie (druk en waaierpomp
spuitmasjiene) te optimiseer, is kommersiële wyn- en tafeldruiwe (Chenin blanc en
Waltham Cross, onderskeidelik), volgens huidige spuit aanbevelings vir wingerde tydens
verskillende groeistadiums en met ‘n reeks van verskillende spuitvolumes gespuit. Die
konsentrasie van die spuitmengsel is dienooreenkomstig gewysig, i.t.v. ‘n vaste dosis per
hektaar ongeag die spuitvolume. Bedekkingswaardes is met FPC75 waardes vergelyk en
het aangedui dat kommersiële spuit aanbevelings aan produsente sal lei tot sub-optimale
beheer van B. cinerea op beide blare en druiwetrosse.
In die algemeen was bedekkingswaardes vir beide druk- en waaierpomp
spuitmasjiene soortgelyk. Vir die waaierpomp teen verskillende spuitvolumes en
aanbevole konsentrasie het ‘n toename in spuitvolumes tot hoër beddekingswaardes gelei,
maar indien die dosis per hektaar van die spuitmengsel konstant behou is, is geen
betekenisvolle verskille tussen spuitvolumes (250-1000 L/ha) voorspel nie. Hierdie dui
aan dat die waaierpomp net so doeltreffend, maar meer effektief teen laer spuitvolumes
gebruik kan word. Die drukpomp was nie so doeltreffend teen hoër spuitvolumes (> 500
L/ha) nie, maar was aansienlik beter by lae volume konsentraat toediening (≈ 250 L/ha op
4 × konsentrasie). Die studie toon duidelik die doeltreffendheid en moontlike kostebesparing
moontlikhede deur bespuiting relatief tot bespuitingstegnologie te optimiseer. / Department of Plant Pathology, National Research Foundation, THRIP, Deciduous Fruit
Producers’ Trust, Winetech, Bayer, BASF, Dow Agrosciences, DuPont, Syngenta, Nexus,
Terason, UAP and Wenkem for financial assistance
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Ácaros predadores do Estado de São Paulo, com ênfase em Laelapidae (Acari: Mesostigmata), com potencial de uso no controle de pragas de solo / Predatory mites of the State of São Paulo, with emphasis on Laelapidae (Acari: Mesostigmata) potentially useful for the control of soil pestsFreire, Renata Angélica Prado 23 March 2007 (has links)
A fauna edáfica em ecossistemas naturais é grande e variada, envolvendo em escala considerável os ácaros. Dentre os vários grupos de ácaros presentes no solo, destaca-se a Ordem Mesostigmata, por compreender um grande número de espécies, muitas das quais predadoras de outros artrópodes edáficos. Diversas pragas agrícolas, como espécies de ácaros, tripes e dípteros da família Sciaridae vivem no solo ou nele passam parte do seu ciclo. Tem-se verificado em outros países que algumas dessas pragas são atacadas e podem em certos casos ser controladas por predadores Mesostigmata. Entre os predadores mais estudados deste grupo estão os pertencentes à família Laelapidae. O Brasil tem sido citado como um país de "mega-diversidade" biológica. Compete aos pesquisadores despenderem esforços no sentido de detectar a possibilidade de uso prático desta diversidade. Os objetivos deste trabalho foram a elaboração de um catálogo com informações taxonômicas para espécies de Laelapidae pertencentes às subfamílias Hypoaspidinae e Melittiphinae que ocorrem no mundo, a identificação dos gêneros de ácaros Mesostigmata edáficos e das espécies de ácaros da família Laelapidae coletados em trabalhos anteriores e que permaneciam não identificados na coleção acarológica do Laboratório de Acarologia da Escola Superior de Agricultura "Luiz de Queiroz"-Universidade de São Paulo, a descrição de espécies novas de Laelapidae encontradas naquele material; a elaboração de chaves taxonômicas para auxiliar na distinção dos gêneros mencionados no catálogo elaborado e das espécies determinadas neste estudo, a avaliação preliminar do uso prático de predadores encontrados naturalmente no Estado de São Paulo para o controle de pragas edáficas e o desenvolvimento de um método para a produção massal de uma espécie daquele grupo. Foram realizadas buscas em bancos de dados para a detecção de bibliografia para a elaboração do catálogo, o qual é de grande utilidade para o desenvolvimento de trabalhos com a família Laelapidae, reunindo informações taxonômicas e referências a gêneros e espécies dispersos na literatura internacional. Esse catálogo contém informações sobre 792 espécies que constituem as subfamílias Hypoaspidinae e Melittiphinae. Com base nas características dos ácaros coletados e na literatura, foram elaboradas chaves taxonômicas, fundamentais para pesquisadores que trabalham com Mesostigmata de solo do Estado de São Paulo. Foram coletados ácaros predadores da família Laelapidae em áreas naturais para a realização de testes que indicaram seu potencial de uso em programas de controle biológico de pragas edáficas de várias culturas. Cosmolaelaps sp. n. e Stratiolaelaps scimitus (Womersley) mostraram um bom potencial como agentes de controle biológico sobre pragas de solo. Estimulados pelos resultados obtidos por pesquisadores em outros países com o uso de ácaros Laelapidae no controle de pragas edáficas, e em função da presente demanda de agricultores paulistas, desenvolveu-se também neste trabalho um método de criação massal de um daqueles predadores, Stratiolaelaps scimitus. / The edaphic fauna in natural ecosystems is large and diverse, involving the mites in large scale. Among the groups of soil mites, the Order Mesostigmata is of great importance, because it contains a large number of species, many of which are predators of other edaphic arthropods. Several agricultural pests, as mites, thrips and Sciaridae flies, live in the soil or spend part of their cycles in it. It has been verified in other countries that some of these pests are attacked and in some cases can be controlled by Mesostigmata predators. Some of the best studies predators of this group are species of Laelapidae. Brazil has been cited as a country of " biological megadiversity" . It is expected that the Brazil?s researchers dedicate efforts to detect the possible practical use of this diversity. The objectives of this work were the publication of a catalog with taxonomic information on the world species on the subfamilies Hypoaspidinae and Melittiphinae (Laelapidae), the identification of the genera of edaphic Mesostigmata and of the species of laelapids collected in previous works and remaining unidentified in the acarology collection of the Acarology Laboratory of Escola Superior de Agricultura "Luiz de Queiroz" -Universidade de São Paulo, the description of new species of Laelapidae found in that material, the construction of taxonomic keys to assist in the separation of the genera mentioned in the catalog and of the species determined in this study, the preliminary evaluation of the practical use of predators naturally occurring in the State of São Paulo for the control of edaphic pests and the development of the mass production of a species of that group. Literature searches were conducted to detect publications to be included in the catalog, which is of great importance for the development research on Laelapidae, for putting together taxonomic information and references on the genera and species of this family that is disperse in international literature. Based on the characteristics of the collected mites and literature information, taxonomic keys, fundamental tools for researchers that work with edaphic Mesostigmata of the State of São Paulo, were prepared. Laelapid species were collected in natural areas to test their potential use in programs of biological control of edaphic pests. Stimulated by the results of authors of other countries in relation to the use of laelapid mites in the control of edaphic pests, and because of the present demand of growers of the State of São Paulo, a method of mass production of those predators was also developed in this work.
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