The diversity and ecology of mites (acari) in vineyards

Vermaak, Mia (2019-03)

Thesis (MScConsEcol)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The common grapevine (Vitis vinifera L.) is the main species used for wine making, with South Africa being one of the top wine exporting countries. Grapevine is vulnerable to a range of pests, one of these being mites. Plant-parasitic mites are extremely damaging pests with a rapid generation time, high fecundity and a tendency to over-exploit their hosts. Disconcertingly, the diversity of mites in vineyards in South Africa is virtually unknown. Surveys have been done with predatory mites and phytophagous mites being recorded, but no recent studies focussing on their ecology, pest status and seasonal cycles have been collected. The aim of this study was to survey phytophagous and predatory mite diversity and to investigate pest status of the plant feeding mites of South African grapevine, including the recently introduced, invasive Brevipalpus lewisi. Sampling was done over a two-year period and included four conventional farms and one organic farm found in the Winelands region of the south Western Cape, South Africa. Each conventional farm contained a motherblock, nursery and commercial vineyard while the organic vineyard only consisted of a commercial vineyard. At each site vine branches were collected on a regular basis from November 2016 to April 2018. During the winter months weed and cover crop samples were also collected at the conventional farms. Mites were collected from vine leaves with a mite brushing machine. Weeds and cover crops were inspected with a microscope and mites were collected from them with a fine brush. Mites were slide mounted and identified. The predatory mite diversity from plant samples was much higher than expected. Eueseius addoensis and Typhlodromus praeacutus were the most abundant predatory mites found in the commercial vineyards and nursery material with T. praeacutus and Neoseiulus barkeri the most common in motherblocks. Brevipalpus species were the abundant phytophagous mites, with Tetranychidae being less abundant. Brevipalpus lewisi was the most dominant species. It did not cause any visual symptoms of damage on the vine. Brevipalpus lewisi did not seem to have natural enemies that were at sufficient densities to affect any control. The seasonal cycles for the predatory and phytophagous mites were established over a period of two seasons; from November 2016 to May 2017 and from November 2017 to April 2018. In commercial vineyards E. addoensis and T. praeacutus were the only predatory mites that were present throughout the entire season. The other predators were present for one or two months. Motherblocks and nurseries had sporadic occurrences of predators. In all three vineyard blocks B. lewisi was dominant throughout the seasons. The organic vineyard survey showed a high diversity of predatory mites and an absence of plant-feeding mites. The dominant predators were also E. addoensis and Typhlodromus saevus. In this study it was found that the main grapevine mites did not migrate to alternate hosts like the cover crops and weeds during winter. Mites that were found on both ground cover and vines were Tydeus grabouwi and Tetranychus ludeni. The findings of this study forms baseline data to develop management strategies to be used in the wine industry. Understanding the diversity and seasonal cycles of the mites occurring on grapevine will make for better decision making in pest control.

AFRIKAANSE OPSOMMING: Die wingerdplant (Vitis vinefera L) is die vernaamste plantspesies wat by wynproduksie in SuidAfrika, een van die voorste wynuitvoerlande, betrokke is. Die wingerdplant is vatbaar vir ‘n reeks plae, waarvan myte ‘n belangrike een is. Plantparasitiese myte kan groot skade aanrig weens hul hoë voortplantingstempo, hoë vrugbaarheid en hul geneigdheid om hul gashere uit te buit. Ongelukkig is die diversiteit van myte wat in wingerde voorkom, feitlik onbekend. Voorlopige opnames is al van plantvretende myte en roofmyte gemaak, maar geen navorsing is al oor hul ekologie, plaagstatus en seisoenale siklusse gedoen nie. Die doel van hierdie studie was om ‘n opname te maak van die plantvretende en roofmyte, en om die plaagstatus te bepaal van die plantvretende myte wat in Suid-Afrikaanse wingerde voorkom. Die status van Brevipalpus lewisi wat onlangs bekendgestel is, is ook ondersoek. Monsters is oor ‘n typerk van twee jaar op vier konvensionele plase en een organiese plaas in die Wynlandstreek van die Suidwes-Kaap in die provinsie Wes-Kaap in Suid-Afrika versamel. Op elke konvensionele plaas was daar ‘n moederblok, ‘n kwekery en ‘n kommersiële wingerd. Die organiese plaas het slegs ‘n kommersiële wingerd gehad. Wingertakke is op elk van hierdie plase op ‘n gereelde tydperk van November 2016 tot April 2018 versamel. Gedurende die wintermaande is onkruid en dekgewasse op die vier konvensionele plase ook versamel. Myte is met die hulp van ‘n mytborselmasjien van wingerdblare versamel. Die onkruid en dekgewasse is met ‘n mikroskoop ondersoek en die myte is met ‘n fyn kwas verwyder. Al die myte is op skyfies gemonteer en geïdentifiseer. Die diversiteit van roofmyte in die wingerde was hoër as wat verwag is. Eueseius addoensis en Typhlodromus praeacutus was die volopste roofmyte in die kommersiële wingerde en kwekerye met T. praeacutus en Neoseiulus barkeri die volopste in die moederblokke. Brevipalpus-spesies was die dominante plantvretende myte terwyl Tetranychidae skaarser was. Brevipalpus lewisi was die vernaamste plantvretende spesies. Hierdie spesies het geen natuurlike vyande nie, en geen fisieke simptome van skade is op die wingerdblare opgemerk nie. Die seisoenale siklusse vir die roofmyte en plantvretende myte was vasgestel oor ‘n tydperk van twee seisoene; van November 2016 tot Mei 2017 en van November 2017 tot April 2018. In die kommersiële wingerde was E. addoensis and T. praeacutus die enigste roofmyte wat gedurende die hele seisoen teenwoordig was. Al die ander roofmyte was vir slegs een of twee maande teenwoordig. Die roofmyte in die moederblokke en kwekerye het sporadies voorgekom. By al drie wingerdblokke was B. lewisi regdeur die seisoen dominant. Die organiese studie het ‘n hoë diversiteit roofmyte getoon en ‘n afwesigheid van plantvretende myte. Die vernaamste roofmyte was E. addoensis en Typhlodromus saevus. In die studie is gevind dat wingerdmyte nie na alternatiewe gasheerplante soos onkruid en dekgewasse migreer nie. Die myte wat wel op dekgewase sowel as wingerde aangetref is, was Tydeus grabouwi en Tetranychus ludeni. Die bevindings van hierdie navorsingstudie vorm die grondslag waarop pesbestuurstrategieë ontwikkel kan word om die wynbedryf en myt-ekologie te bevorder. Danksy begrip van die diversiteit en seisoenale siklusse van myte wat op wingerdblare voorkom, kan beter besluite geneem word vir die bestuur van peste.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105600
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