Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The commercial cultivation of Proteaceae is an important industry in the Western Cape,
however, farmers are challenged with arthropod infestation which compels them to solely
rely on chemical pesticides. Past studies in South Africa have shown that Proteaceae
comprise a rich and diverse arthropod fauna. However, as most of these studies were
conducted on wild Proteaceae, they may not be representative of cultivated proteas.
Moreover, most of these species remained unidentified due to lack of identification expertise.
These past studies, however, form a useful baseline for arthropod studies in proteas, e.g. the
feeding guilds found in proteas. The aim of this research was to conduct an intensive and
extensive survey of the arthropod-fauna associated with commercially-cultivated proteas
across an entire year. Specifically, this survey was designed to document the composition of
the arthropod fauna (creating a comprehensive reference collection for pest management
purposes) and to assess whether the arthropod fauna differed between seasons and pesticide
treatments.
Infructescences, inflorescences and foliage of mainly commercial Proteaceae were sampled
for arthropods seasonally for a period of twelve months by collection of plant material and
direct searching. Seven commercial protea blocks, and a wild protea block (remnant patch of
fynbos vegetation), were used as the sampling sites, and two sprayed blocks were used for
assessing pesticide efficacy. Individual arthropods were identified as far as possible, with
37% identified to species level. A species accumulation curve showed that rare (minor)
arthropod species made up of 70% of arthropods occurring in cultivated proteas.
More than 8 700 individuals from more than 140 species and about 80 families were
collected and identified, revealing that cultivated proteas have a rich and diverse insect fauna.
These arthropods represent the full range of plant-feeding guilds: leaf miners, leaf chewers,
flower bud borers, sap suckers and seed feeders. Flower visitors/free living guild was the
most abundant (72%) and speciose (25%). In addition to phytophages, there was a large suite
of insect predators and parasitoids. A large number of the arthropods were endemic to the
Cape Floristic Region (CFR) and some (7.86%) have a pest status, in that they cause
significant damage to the protea plants (for example, 60% of Safari sunset cultivar
(Leucadendron salignum x L. laureolum) new flush stems and leaves were affected by
Epichoristodes acerbella (Tortricidae). Capys alphaeus (Lycaenidae) and Phyllocnistis sp.
(Phyllocnistidae) appear to be specialist pests, as they attack mainly Protea cynaroides and
Susara cultivar (Protea magnifica x P. susannae) respectively.
Arthropod abundance did not differ significantly between seasons, although significant
seasonal effects were observed in species richness when the protea cultivars were examined
separately. Pesticide application did not affect arthropod abundance, but did decrease species
richness in sprayed blocks. Pesticides appeared to negatively affect minor (rare) species
disproportionately, probably due to their lack of prior exposure to pesticides and hence
sensitivity. Due to this inefficacy of pesticides in cultivated proteas, an increasing emphasis
on the importance of non-chemical control measures, and our improved knowledge of the
predatory and parasitic species in this system, integrated pest management strategies deserve
greater research attention.
Monitoring and use of threshold values for arthropod pests were suggested here, as well as
the use of biological, cultural, physical and chemical (optimal use) control. For instance, in
cultural control, polycropping and intercropping in proteas to increase plant diversity in the
monocultures to promote a higher density of predators and parasitoids can be used. Certain
flowering plants are known to provide greater temporal and spatial distribution of nectar and
pollen sources, which can increase parasitoid reproductive potential and abundance of
alternative hosts/prey when the pest species are scarce or at an inappropriate stage. / AFRIKAANSE OPSOMMING: Die kommersiële verbouing van Proteaceae (proteas) is 'n belangrike bedryf in die Wes-Kaap.
Menige plantasie wemel egter van artropodes, wat boere noop om slegs van chemiese
plaagdoders gebruik te maak. Vorige studies in Suid-Afrika toon dat proteas die gasheerplant
vir 'n ryke en diverse artropodefauna is. Aangesien die meeste van hierdie studies egter op
wilde proteas uitgevoer is, weerspieël dit moontlik nie die stand van sake met verboude
proteas nie. Weens 'n gebrek aan kundigheid om die artropodes te eien word baie van die
spesies boonop nooit uitgeken nie. Dié studies voorsien egter 'n nuttige grondlyn vir 'n
ondersoek na die artropodes op proteas, veral vir die bestudering van die gilde wat van die
protea leef (“the feeding guild”). Hierdie navorsing het ten doel om 'n intensiewe en
omvattende opname te maak van die artropodefauna wat oor die tydperk van 'n jaar op
kommersieel verboude proteas voorkom. Die opname is meer bepaald ontwerp om die
samestelling van die artropodefauna te bestudeer (deur 'n omvattende verwysingsversameling
vir plaagbestuurdoeleindes te skep), en om vas te stel of seisoene en plaagbehandelings enige
beduidende uitwerking op die artropodefauna het.
Oor 'n tydperk van 12 maande is seisoenale monsters van die vrug- en bloeistadia, saadkoppe
en blare van hoofsaaklik kommersiële proteas gesoek en ingesamel. Sewe kommersiële
proteablokke sowel as 'n blok wilde proteas het as proefpersele gedien, en twee bespuite
blokke is gebruik om die doeltreffendheid van plaagdoder te beoordeel. Individuele
artropodes is so noukeurig moontlik uitgeken – 37% tot op spesievlak. Volgens 'n
spesieakkumulasiekurwe maak seldsame (kleiner) artropodespesies sowat 70% van die
artropodes uit wat op verboude proteas voorkom.
Die meer as 8 700 individue van meer as 140 spesies en sowat 80 families wat ingesamel en
uitgeken is, toon die rykheid en diversiteit van die artropodefauna op verboude proteas.
Hierdie artropodes verteenwoordig die volle reeks plantvreterspesies – van blaardelwers en
blaarkouers tot blomknopboorders, sapsuiers en saadvreters. Blombesoeker-/vrylewende
spesies was die volopste (72%) en mees divers (25%). Buiten plantvreters was daar ook 'n
groot aantal roofinsekte en parasitoïede. Baie van die artropodes was inheems, en sommige
(7,86%) het boonop plaagstatus, aangesien hulle beduidende skade aan die proteaplant aanrig.
[By ongeveer 60% van die Safari Sunset-kultivar (Leucadendron salignum x L. laureolum) is
nuwe stamme en blare byvoorbeeld deur die Epichoristodes acerbella (Tortricidae)
aangetas.] Capys alphaeus (Lycaenidae) en Phyllocnistis sp. (Phyllocnistidae) blyk
spesialisplae te wees wat onderskeidelik hoofsaaklik die Protea cynaroides en die Susarakultivar
(Protea magnifica x P. susannae) in die visier het.
Artropodegetalle het nie juis tussen seisoene gewissel nie, hoewel 'n afsonderlike ondersoek
van die proteakultivars 'n beduidende seisoenale uitwerking op spesierykheid aan die lig
gebring het. Eweneens het die toediening van plaagdoder nie die artropodegetalle verminder
nie, maar wel spesierykheid op die bespuite blokke verswak. Plaagdoders blyk besonder
negatiewe uitwerking op kleiner (seldsame) spesies te hê – waarskynlik omdat dié spesies nie
voorheen aan plaagdoders blootgestel was nie, en dus gevoelig is daarvoor. Weens die
oënskynlike ondoeltreffendheid van plaagdoders op verboude proteas, verg 'n toenemende
klem op die belang van niechemiese beheermaatreëls, 'n behoefte aan meer kennis van die
roof- en parasitiese spesies in die stelsel, en die vraag na geïntegreerde plaagbeheerstrategieë,
meer navorsing.
Die studie moniteer en gebruik drempelwaardes vir artropodeplae, sowel as biologiese,
kulturele, fisiese én chemiese (‘optimalegebruik’-) plaagbeheer. Met kulturele beheer kan
poli- en interverbouing van proteas byvoorbeeld gebruik word om plantdiversiteit in die
monokulture te verbeter, ten einde só 'n hoër digtheid van roofspesies en parasitoïede in die
hand te werk. Sekere blomplante bied kenmerkend 'n wyer tyd- en ruimtelike verspreiding
van nektar- en stuifmeelbronne, wat parasitoïede se voortplantingsvermoë en die getalle van
alternatiewe gashere/prooi kan verbeter wanneer die plaagspesies skaars is of in 'n
ontoepaslike stadium verkeer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6805 |
| Date | 03 1900 |
| Creators | Sasa, Archbold |
| Contributors | Samways, Michael John, University of Stellenbosch. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 219 p. ; ill. |
| Rights | University of Stellenbosch |
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