Distribution of pests of blueberries in South Africa and re-description and behaviour of the blueberry bud mite Acalitus vaccinii (Eriophyidae)

Ngubane, Nompumelelo Pretty (2018-12)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Blueberries (Vaccinium spp. (Ericaceae)) are native to North America. Their production in South Africa was established about 32 years ago. South Africa exports about 80% of produced blueberries to the northern hemisphere. The blueberry industry is small compared to other fruits and challenges facing this industry includes limited use of pesticide on soft fruits and the lack of research on this crop. The aim of the present study was to document the main factors that affect arthropod species richness, abundance and communities in blueberry orchards of South Africa. Factors investigated included orchard location, season, production type (open fields versus production in tunnels) and pesticide usage (organic versus inorganic farming). Arthropods were collected from six farms in the Mpumalanga and Western Cape Provinces using vacuum and clipping sampling methods. Arthropods were grouped into dominant feeding guilds to assess the impact of these factors on pests and beneficial taxa. There was a significant variation in arthropod numbers throughout the year with numbers of all taxa peaking during warmer months. Different localities often had different arthropod species, numbers and composition. Fields with fewer predators and parasitoids tended to have higher number of plant feeding species. Production of blueberries in tunnels did not necessarily reduce pest numbers, but rather, different pest species reacted differently towards these production methods. Organic fields housed similar numbers of phytophagous species as inorganic fields indicating that pesticide usage does not necessarily aid in pest control on blueberries. Organic production is therefore advocated to maximise numbers of beneficial species while also resulting in greater profitability. As the South African blueberry industry grows, more pests will likely be reported. In 2014, the blueberry bud mite, Acalitus vaccinii Keifer (Acari: Trombidiformes: Eriophyidae) was reported for the first time at one farm in Mpumalanga Province. Internationally it is known as one of the most significant pests of blueberries. In South Africa it caused nearly 80% reduction in fruit yield within two years of detection. Identification of eriophyoid mites requires a high level of expertise and this challenge is intensified by a lack of identification keys and good quality species descriptions. The species description of A. vaccinii was published in 1939 and no longer meets modern standards for species description in this group. I therefore revised the original descriptions, and described all stages of the mite including the female, male and immatures. The male was described here for the first time. The original description was improved by addition of information and characters using new microscopy techniques such as phase contrast light microscopy and scanning electron microscopy. I also compiled a key to all Eriophyoidea species known on blueberries around the world to aid future identification. The biology of A. vaccinii in South Africa is discussed. This study investigates the role of beneficial taxa and pest species in blueberry orchards in South Africa. It thus provides baseline information to aid in development of pest management strategies in blueberry orchards in South Africa, with particular emphasis on the newly introduced blueberry bud mite.

AFRIKAANSE OPSOMMING: Bloubessies (Vaccinium spp. (Ericaceae)) is inheems tot Noord Amerika. Produksie in Suid Afrika het omtrent 32 jaar gelede begin. Suid Afrika voer ongeveer 80% van sy bloubessie produksie uit na die noordelike halfrond. Die bloubessie industrie is klein vergeleke met ander vrugte en uitdaagings met hierdie industrie sluit die gelimiteerde gebruik van gifstowwe en die gebrek van navorsing op hierdie gewas in. Die doel van die huidige studie was om die hoof faktore wat n effek het op artropood spesie rykheid, hoeveelheid en populasies in bloubessie boorde in van Suid Afrika te dokumenteer. Ondersoekte faktore het boord lokaliteit, seisoen, produksie tipe (oop veld teenoor produksie tonnels) en gifstof gebruik (organies teenoor anorganiese boerdery) ingesluit. Arthropoda was versamel vanaf ses verskillende plase in die Mpumalanga en in die Wes Kaap provinsies met behulp van ‘m blaar suigtoestel en knip-versamel metodes en gegroepeer in dominante voedingsgroepe. Daar was merkbare variasie in artropood getalle gedurende die jaar met meete taxa wat gepiek het gedurende die warmer maande. Verskillende lokaliteite het meestal verskillende spesies, getalle en komposisies gehad. Velde met minder predatore en parsitoïdes was geneig om hoër getalle plantvoedende spesies te huisves. Produksie van bloubessies in tonnels het nie noodwendig laer pegetalle gehad nie nie, maar eerder, verskillende pes spesies het verskillend gereageer op verskillende produksie metodes. Organiese velde huisves soortgelyke hoeveelhede plantvoedende spesies as anorganiese velde. Dus, die gebruik van kiemdoder help nie noodwendig met pes beheer op bloubessies nie. Organiese produksie word dus geadviseer om getalle voordelige spesies te optimiseer en terselfdertyd groter winsgewendheid te bevoordeel. Soos die Suid Afrikaanse bloubessie bedryf groei, sal daar waarskynlik meer peste gerapporteer word. In 2014, was die bloubessie bot myt, Acalitus vaccinii Keifer (Acari: Trombidiformes: Eriophyidae) gerapporteer op een ‘n plaas in die Mpumalanga Provinsie. Internasionaal is dit bekend as as een van die mees beduidende peste op bloubessies. In Suid Afrika het dit amper 80% reduksie in vrug opbrengs in slegs twee jaar van monitoring veroorsaak. Identifikasie van eriophoied myte benodig höe vlak van kundigheid en dit word verder bemoeilik deur ‘n tekort aan goeie identifikasie sleutels. Die spesie beskrywing van A. vaccinii was gepubliseer in 1939 en voldoen nie aan modrne standaarde vir spesie beskrywing nie. Dus het ek die oorspronklike beskrywings hersien en alle lewensfases, insluitend vroulike, manlike en onvolgroeides, herbeskryf. Die manlike vorm word hier vir die eerste keer beskryf. Die oorspronklike beskrywing was verbeter deur die byvoeging van informasie en karaktertrekke met behulp van nuwe mikroskoop tegnieke soos fase kontras lig mikroskopie en elektron miskroskopie. Ek het ook n sleutel vir alle Eriophyoidea spesies bekend vanaf bloubessies ter wereld saamgestel. Die biologie van A. vaccinii in Suid Afrika word bespreek.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105062
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