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dc.contributor.advisorLouw, S. VDM.en_ZA
dc.contributor.authorHugo, Elizabeth Aletta
dc.date.accessioned2018-04-19T11:05:41Z
dc.date.available2018-04-19T11:05:41Z
dc.date.issued2000-11
dc.identifier.urihttp://hdl.handle.net/11660/8216
dc.description.abstractEnglish: Biodiversity is a non-detachable part of the concept of sustainable agriculture. The reliance on only a few crop species in the agricultural landscape poses special problems and risks due to biotic hazards. To enhance diversity, agriculture must diversify crop production and exploit under-utilized and new crops. Amaranthus hybridus is such a crop and has great potential due to its hardiness and high nutritional value. Acceptable crop yield depends on the influence of insects. Some sort of pest management thus forms an integral part of agriculture. Due to detrimental effects on the environment and the high cost of pesticides, farmers are looking for alternative low cost methods, which will provide a long-term solution for pest problems. Cultivation practices are one such method, which aim to enhance natural enemy performance. This study was conducted near the Tempe airport, 20 km northwest of Bloemfontein (SE 2926Aa) in the Free State. A monoculture trial was run in 1997 and 1998, a mixed crop setup in 1998 and a staggered planting date culture in 1999. Monoculture, the most widely used method of farming in the Free State, reduces a complex natural ecosystem to a single plant species environment, resulting in more visual and chemical stimuli for flying phytophagous species, prompting them to land more readily than in a more diverse plant environment. Thus, large populations of phytophages occur in the mono culture, some of which, due to favourable microelimate could develop to pest status. Mixed cropping is a more diverse plant system, thus presenting a greater diversity of niches and consequently a higher diversity of arboreal phytophages and natural enemies. Adjusting planting and harvesting time, such as staggered planting dates, can be used to escape pest damage and keep it below economic levels. By planting early sure pests population peaks can be avoided. The terrestrial insect community is also of major importance, since many predators are groundliving. Terrestrial insects are influenced by the microelimate and shelter provided by plants and preferred stands in which these factors are at an optimum. In this study it was found that predators are most effective in large, sparse stands. To conserve natural enemies it is important to incorporate permanent habitats like border areas where they can overwinter, build up population numbers and from which they can disperse to newly planted crops. This study promotes conservation biological control, which aims at using and enhancing beneficiais, which are already present, by using different cultivation practices. Farmers often lack the biological and ecological information necessary to develop better pest management. This study was aimed at providing that information to obtain maximum yield in the long term with lower production costs.en_ZA
dc.description.abstractAfrikaans: Biodiversiteit is "n onafskeibare konsep in volhoubare landbou. Daar is sekere gevare en risikos aan verbonde deur net 'n paar gewasse te plant. Landbou moet eerder 'n verskeidenheid gewasse of nuwe gewasse produseer ten einde biodiversiteit te bevorder. Amaranthus hybridus (morogo) is 'n nuwe gewas wat groot potensiaal het a.g.v. sy hoë voedingswaarde en gehardheid. Insekte beinvloed aanvaarbare gewas opbrengs en daarom is een of ander vorm van plaagbestuur 'n integrale deel van landbou. Insekdoders het soms "n nadelige uitwerking op die omgewing en is ook baie duur, daarom soek boere alternatiwe metodes met laer kostes wat langtermyn oplossings vir plaag probleme sal bied. Verbouingspraktyke is een van die alternatiewe metodes en stel ten doelom die effektiwiteit van natuurlike vyande te verbeter. Die huidige studie is gedoen naby die Tempe Lughawe, 20 km noordwes van Bloemfontein (SE 2926Aa) in die Vrystaat. Verskillende verbouingspraktyke is gebruik, nl. 'n monokultuur in 1997 en 1998, 'n wisselbou opset in 1998 en opeenvolgende plant datums in 1999. Monokulture is die algemeenste landbou metode in die Vrystaat. Dit reduseer egter 'n komplekse natuurlike ekosisteem na 'n enkel plant spesie omgewing wat meer visuele en chemiese stimuli vir vlieënde fitofage bied en hulle dus meer aanspoor om te land as in 'n diverse sisteem. Groot getalle fitofage insekte het dus in die monokultuur voorgekom en a.g.v. gunstige omstandighede kan van hulle plaag status bereik. Wisselbou is "n meer diverse plantsisteem met groter diversiteit van nisse en dus ook 'n hoër diversiteit van fitofage en natuurlik vyande. Die aanpassing van plant- en oestye, bv. opeenvolgende plant datums, kan gebruik word om plaagskade te beperk en onder ekonomiese vlakke te hou. Deur vroeg te plant word plaagskade dus verhoed omdat plaag spesies nog nie op daardie stadium piek getalle bereik het nie. Die terrestriële insek gemeenskap is ook belangrik, omdat baie predatore grondlwened is. Hierdie insekte word beïnvloed deur mikroklimaat en skuiling wat deur die plante verskaf word en verkies dus stande waar hierdie faktore optimaal is. In die studie is gevind dat terrestriële predatore groot, yl geplante stande bo digte klein stande verkies. 'n Ander aspek wat belangrik is vir bewaring is om permanente habitatte, bv. randgebeide, vir voordelige insekte daar te stel. Hierdie areas moet geskik wees vir oorwintering, populasie groei en moet 'n platform skep vanwaar hierdie insekte kan versprei sodra gewasse geplant word. Hierdie studie is gebasseer op bewarings biologiese beheer, wat reeds teenwoordige, nuttige insekte gebruik en bevorder deur verskillende verbouingspraktyke Boere het dikwels nie die nodige biologiese en ekologiese inligting wat beter plaag beheer sal verseker nie. Hierdie studie stel ten doelom daardie inligting te verskaf ten einde maksimum opbrengs met laer produksie koste op die langtermyn te lewer.af
dc.description.sponsorshipNational Research Foundation (NRF)en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectAmarantbus hybridusen_ZA
dc.subjectMonocultureen_ZA
dc.subjectMixed croppingen_ZA
dc.subjectStaggered planting datesen_ZA
dc.subjectArboreal insectsen_ZA
dc.subjectTerrestrial insectsen_ZA
dc.subjectRefugiaen_ZA
dc.subjectBorder areasen_ZA
dc.subjectDiversityen_ZA
dc.subjectFeeding guildsen_ZA
dc.subjectAmaranths -- South Africa -- Free Stateen_ZA
dc.subjectAmaranths -- Diseases and pestsen_ZA
dc.subjectDissertation (M.Sc. Zoology and Entomology))--University of the Free State, 2000en_ZA
dc.titleGuild structure and seasonal distribution of insects associated with Amaranthus Hybridus under diverse cultivation practices in the Central Free Stateen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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