Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Several attempts have been made to reduce Botrytis cinerea grey mould in vineyards and
in storage by means of biological control. However, the so called "silver bullet" approach in
utilising a single antagonist, has its limitations when compared with synthetic fungicides.
Often the antagonist has a limited spectrum of activity and the duration of its effectiveness is
less than that provided by synthetic fungicides. Furthermore, antagonists are more likely to
be effective in preventing initial infection rather than resumption of latent infection.
Therefore, due to the various infection sites in grape bunches utilised by B. cinerea and the
fact that the pathogen can remain latent in the grapevine tissue, it may be possible to obtain
effective control of the pathogen by integrating fungicides and different biological control
agents each aimed at a different site in grape bunches, protecting the bunch at the various
phenological stages of growth and under different micro climatic conditions. In this study the
potential of three fungal antagonists (Glioc/adium roseum, Uloc/adium atrum and
Trichoderma harzianum) and one yeast (Trichosporon pullulans) to colonise different sites in
grape bunches, and to reduce B. cinerea infection, was investigated in commercial vineyards.
As the biological control agents were used in an integrated system, the effect of various
fungicides frequently applied to local vineyards on the organisms was also investigated.
Fungicide trials were conducted taking into account two possible scenarios. Firstly, the
possible effect of fungicides applied to the vineyard after an application of the biological
control agent or shortly before the application of the biocontrol agent. This entailed exposing
the biocontrol agents to relatively low concentrations of the active ingredient of the
fungicides, similar to the residue levels to which these organisms would be exposed under
field conditions. Secondly, the possibility of applying the organisms and the fungicides at the
same time by making use of spray tank mixtures. This meant exposing the biocontrol agents
to relatively high doses of the active ingredient of the various fungicides. Mycelial growth
and germination tests were performed on agar in Petri dishes to determine the effect of
fungicides. It was assumed that if the fungicide effectively inhibits the antagonist at 2.5 !-lg a.Uml, the fungicide and antagonist can not be used in an integrated programme. Based on
this criterium, T harzianum can not be applied to vineyards with penconazole,
mancozeb/metalaxyl, pyrifenox or mancozeb. In addition T harzianum can not be applied as
tank mixtures with iprodione. However, T harzianum can be used in conjunction with
pyrimethanil, folpan, iprodione, fosetyl-Al and copperhydroxide, provided the chemicals and
the antagonist are applied alternately. Gliocladium roseum can not be applied in a tank
mixture with pyrimethanil and penconazole, but can be used on grapevine in conjunction with
penconazole, pyrifenox, pyrimethanil, iprodione and fosetyl-Al. Ulocladium atrum can not
be applied with pyrimethanil and iprodione. Ulocladium atrum can be applied in conjunction
with penconazole, pyrifenox, pyrimethanil, iprodione, fosetyl-Al and mancozeb. The fungus
can be applied in a tank mixture with penconazole and pyrifenox.
The antagonists were applied as conidial suspensions to bunches at various phenological
stages in commercial vineyards planted with the wine grape cultivar Chardonnay in the
Stellenbosch region, or the table grape cultivar Dauphine planted in Paarl region. Bunches
were collected 2 wk after application, surface-sterilised and used for determining antagonist
colonisation and B. cinerea infection at specific sites in the bunches. In Chardonnay, the
antagonists colonised the different sites, but colonisation during the three seasons was
inconsistent and sporadic. Ulocladium atrum and G. roseum colonised floral debris to a
degree in the 1996 season. However, in the 1997 season these two antagonists did not
develop from floral debris. Trichoderma harzianum colonised floral debris extensively in the
1996 season. In the 1997 season colonisation by T harzianum dropped, but unlike G. roseum
and U atrum, T harzianum occurred at a low level in flowers. Ulocladium atrum only
colonised bunches during bloom, and was not found in bunches monitored from pea-size
stage to véraison. This finding suggests that the saprophyte colonised moribund and dead
flower parts occurring in bunches during full bloom to the pre-pea size stage, and is not likely
to be found in living tissue. Gliocladium roseum colonised grape berries and pedicels to
some degree and T harzianum colonised these grape parts extensively. Botrytis cinerea
occurred inconsistently and at low frequencies in the different sites in bunches. It was
therefore not possible to comment on the effectivity of the various antagonists in the three
seasons during which the trials were performed. However, it was noted that, during the peasize
stage in 1996, when high levels of B. cinerea were recorded, T harzianum controlled
these infections in the pedicels more effectively than any other treatment. / AFRIKAANSE OPSOMMING: ONDERDRUKKING VAN BOTRYTIS CINEREA DEUR ANTAGONISTE IN
LEWENDE, AFSTERWENDE EN DOOIE WINGERDWEEFSEL
Die benadering om Botrytis cinerea verrotting van wingerd met behulp van 'n enkele
biologiese beheeragent in plaas van met sintetiese fungisiede te beheer, het sekere
beperkinge. Antagoniste het dikwels 'n beperkte spektrum van aktiwiteit, en die duur van hul
effektiwiteit is minder as dié van fungisiede. Antagoniste is gewoonlik ook minder effektief
in die beheer van latente infeksie. Die patogeen het verder die opsie om druiwetrosse deur
verskillende infeksieweë te koloniseer. Fungisiede kan druiwetrosse beter teen infeksie deur
veelvuldige infeksieweë beskerm as 'n enkele antagonis. In die lig hiervan is die beheer van
die patogeen deur 'n kombinasie van fungisiede en verskillende biologiese beheeragente, wat
elk gemik is om 'n ander infeksiepunt in die druiwe te beskerm, ondersoek. Drie swamagtige
antagoniste (Glioc/adium roseum, Uloc/adium atrum en Trichoderma harzianum) en een gis
(Trichosporon pullulans) is in die ondersoek gebruik.
Voorloper ondersoeke, waar twee moontlike scenarios in ag geneem is, is met fungisiede
uitgevoer. In die eerste scenario is die effek van fungisiede, aangewend op wingerd kort vóór
aanwending van die biologiese beheeragent, of kort ná aanwending, ondersoek. Hierdie
proef het die blootstelling van die biologiese beheeragent aan relatief lae konsentrasies van
die aktiewe bestanddeel van die fungisied, vergelykbaar met residuvlakke waaraan die
organismes onder veldtoestande blootgestel sou word, behels. Tweedens is die moontlikheid
om antagoniste en fungisiede gelyktydig as spuitpompmengsels toe te dien, ondersoek. In
hierdie proef is die biologiese beheeragente aan relatief hoë dosisse van die aktiewe
bestanddeel van verskillende fungisiede blootgestel. Miseliumgroei en ontkiemingstoetse is
op agar in Petribakkies uitgevoer om die effek van die fungisiede te bepaal. As kriterium is
aanvaar dat indien 'n fungisied die antagonis effektief by 2.5J..lglml aktiewe bestanddeel
inhibeer, die fungisied en antagonis nie in 'n geïntegreerde program gebruik kan word nie.
Gebaseer op hierdie kriterium kan T harnzianum nie aangewend word in 'n wingerd wat met
penconazole, mancozeb/metalaxyl, pyrifenox of mancozeb behandel is nie. Ook kan T
harzianum nie in 'n spuitpompmengsel met iprodione aangewend word nie. Trichoderma harzianum kan egter saam met pyrimethanil, folpan, iprodione en fosetyl-Al gebruik word,
mits dié chemikalieë en die antagonis afwisselend aangewend word. Glioc/adium roseum
kan nie in 'n spuitpompmengsel met pyrimethanil en penconazole aangewend word nie, maar
kan saam met penconazole, pyrifenox, pyrimethanil, iprodione en fosetyl-Al gebruik word.
Uloc/adium atrum kan nie saam met pyrimethanil, iprodione en fosetyl-Al gebruik word nie.
Die swam kan wel in 'n spuitpompmengselmet penconazole en pyrifenox aangewend word.
In verdere proewe is die antagoniste as spoorsuspensies op trosse op verskillende
groeistadia in kommersiële wingerde, wat met die wyndruitkultivar Chardonnay of die
tafeldruifkultivar Dauphine aangeplant is, ondersoek. Trossies is twee weke na toediening
versamel, oppervlakkig gesteriliseer en gebruik om vlakke van antagoniskolonisasie en B.
cinerea infeksie op spesifieke nisse in die trosse te bepaal. In die geval van Chardonnay het
die antagoniste die verskillende nisse gekoloniseer, maar die kolonisasie was sporadies en nie
konstant gedurende die drie seisoene van ondersoek nie. Uloc/adium atrum en G. roseum het
blomdeeltjies tot 'n beperkte mate in die 1996 seisoen gekoloniseer, maar nie in die
daaropvolgende seisoen nie. Daarteenoor het T. harzianum blomdeeltjies ekstensief in die
1996 seisoen gekoloniseer, en in 'n beperkte mate in die daaropvolgende seisoen.
Uloc/adium atrum kon nie trosse van ertjiekorrelgrootte tot deurslaan vestig nie. Hierdie
bevinding dui daarop dat die saprofiet afsterwende en dooie blomdeeltjies, wat van volblom
tot ertjiekorrelstadium in die trosse voorkom, koloniseer, maar dat dit nie in lewende weefsel
voorkom nie. Daarteenoor het T. harzianum die verskillende trosdele ekstensief
gekoloniseer. Botrytis cinerea het gedurende die drie seisoene wisselvallig en teen lae
frekwensies in die verskillende nisse in die trosse voorgekom. Dit was gevolglik nie
moontlik om 'n konkrete afleiding oor die effektiwiteit van die verskillende antagoniste as
biobeheeragente van B. cinerea te maak nie.
In die geval van Dauphine was die onderskeie organismes swak koloniseerders van
blomdeeltjies. Trichoderma harizanum kon egter die lewende trosdele koloniseer.
Kolonisasievlakke was laag en was nooit meer as 50% nie. In beide seisoene het die
kolonisasievermoë van T. harzianum drasties ná trostoemaak gedaal. Daarteenoor het beide
G. roseum en U atrum tydens al die ontwikkelingstadia die lewende trosdele swak
gekoloniseer. Botrytis cinerea het ook uiters sporadies en teen baie lae vlakke voorgekom. Die bevindinge het getoon dat klimaatsomstandighede wat in tafeldruifwingerde in die
Wes-Kaap heers, nie geskik is vir die vestiging van die biologiese beheeragente wat in die
studie ondersoek is nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52472 |
| Date | 12 1900 |
| Creators | Volkmann, Anette (Anette Sigrid) |
| Contributors | Holz, G., Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 111 p. : ill. |
| Rights | Stellenbosch University |
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