Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: In surveys carried out on poultry farms in the Western Cape Province, South Africa, the larvae of the flies Musca domestica L., Fannia canicularis (L.) and Leptocera sp. were found to be numerous. The majority of M domestica larvae and the mite Proctolaelaps sp. were recovered from manure with temperatures between 20 and 26°C while the larvae of F. canicularis and Leptocera sp. were mostly found between 14 and 22°C. Predominant predatory arthropods in the manure were the histerid Carcinops pumilio (Erichson), the staphylinid Philonthus sordidus (Gravenhorst) and the mite Macrocheles muscaedomesticae (Scopoli). These had a manure temperature tolerance of between 12 and 31°C. Macrocheles muscaedomesticae and P. sordidus preferred fresh manure, whilst C pumilio preferred aged manure. Therefore these two predators could complement one another in integrated pest management programmes. From a study of the vertical cross-sectional profile of the manure cone it was clear that the larvae of the prey species M domestica and F. canicularis and predator P. sordidus distinctly occupy the crest of the manure cone. The succession of arthropods in accumulating poultry manure and the effect of manure height on their numbers was studied. The prey species M domestica and F. canicularis were the first colonizers followed by the predators P. sordidus and M muscaedomesticae. Carcinops pumilio was a late colonizer. The numbers of M domestica and F. canicularis larvae were negatively correlated with the increase in manure height whilst the numbers of the predators C pumilio and M muscaedomesticae were positively correlated with this. The total developmental time of C pumilio from egg to adult emergence at 30°C was 20.5 days. Two larval instars were recorded. The immature stages sustained about 50% mortality before adult emergence. Carcinops pumilio adults can live up to 130 days at 30°C and had a Type I survivorship curve. The intrinsic rate of natural increase (rm) was 0.064943 and net reproduction rate (Rs) was 20.191.The rate of oviposition was directly proportional to body size and weight. Increase in density had a dampening effect on fecundity and led to an increase in developmental time. Thus density will be a critical factor in any mass rearing programme for this predator of fly larvae. In addition, an increase in density stimulated the dispersal of C. pumilio. A crowding level of 50 C. pumilio adults per 200ml container resulted in the least dispersal which did not exceed 2.5% per day, compared with up to 24.0% at a crowding level of 400. The predation rate of flies by C. pumilio in the laboratory decreased with an increase in predator density, but increased with an increase in starvation. Starvation had no effect on predation rate of M muscaedomesticae. A technique exploiting Drosophila melanogaster Meig. as a source of prey was successfully developed for rearing C. pumilio, which could be of commercial value. Drosophila melanogaster appeared to be an ideal candidate as a source of prey for mass rearing C. pumilio due to its short developmental time of about ten days. It is also inexpensive and easy to breed, and has a very high biotic potential. Carcinops pumilio that were fed on artificial diet had a prolonged developmental time and increase in weight, and laid fewer eggs than those fed on natural diet. C. pumilio completed its development on the artificial diet and both the F, and F2 generations fed on an artificial diet were able to lay eggs. This could be the first step towards finding an artificial diet that would allow continuous rearing of C. pumilio and their availability at all times for utilization in the biological control of houseflies. / AFRIKAANSE OPSOMMING: In opnames wat op pluimveeplase in die Westelike Kaapprovinsie, Suid-Afrika uitgevoer is, is gevind dat die vliegsoorte Musca damestica L., Fannia canicularis (L.) en Leptacera sp. volop is. Die meeste van die M. damestica larwes en die myt Practalaelaps sp. is versamel in hoendermis met temperature tussen 20 en 26°C en die larwes van Ficanicularis en Leptacera tussen 14 en 22°C. Die volopste predatoriese arthropode in die mis was die histerid Carcinaps pumilia Erichson, die staphylinid Philanthus sardidus (Gravenhorst) en die myt Machrascheles muscaedamesticae (Scopoli). Hulle temperatuurtoleransie in die mis was tussen 12 en 31°C. Machrasceles muscaedamesticae en P. sardidus het vars mis verkies, terwyl C. pumilio voorkeur aan ouer mis gegee het. Gevolglik behoort hierdie twee predatore mekaar te komplementeer in programme van ge-integreerde plaagbestuur. In Studie van die vertikale deursnee-profiel van die miskeel het duidelik getoon dat die prooispesies M. damestica en en F canicularis en die predator P. sardidus in die kroon van die miskeel voorkom. Die opeenvolging van die arthropode in die ophopende hoendermis en die invloed van mishoogte op hulle getalle is bestudeer. Die prooispesies M damestica en F canicularis was die eerste koloniseerders, gevolg deur die predatore P. sardidus en M muscaedamesticae. Carcinaps pumilia was In laat koloniseerder. Die getalle van die larwes van M damestica en F. canicularis was negatief gekorreleer met die toename in mishoogte terwyl die getalle van die predartore C. pumilia en M. muscaedamesticae positief daarmee gekorreleer was. Die totale ontwikkelingstyd van C. pumilia van eier tot die volwassene se verskyning was 20.5 dae by 30°C. Twee larwale instars is gevind. Die onvolwasse stadia het 50% mortaliteit ondergaan voor die verskyning van die volwassenes. Die volwassenes van C. pumilia kan tot 130 dae lank by 30°C lewe en het In Tipe 1 oorlewingskurwe gehad. Die intrinsieke tempo van natuurlike toename (rm) was 0.064943 en die netto reproduksietempo (Rs) 20.191. Die tempo van eierlegging was in direkte verhouding tot die liggaamsgrootte en massa. Toename in digtheid het 'n onderdrukkende effek op vrugbaarheid gehad en tot 'n toename in ontwikkelingstyd gelei. Digtheid sal dus 'n kritieke faktor wees III emge program van massateling vir hierdie predator van vlieglarwes. Daarmee saam het 'n toename in digtheid die verspreiding van C. pumilio gestimuleer. By 'n digtheid van 50 C. pumilio volwassenes per houer het die verspreiding nie 2.5% oorskrei nie, in vergelyking met tot 24.0% by 'n dightheid van 400. Die predasietempo van vliee deur C. pumilio in die laboratorium het afgeneem met 'n toename in predatordigtheid, maar toegeneem met 'n toename in verhongering. Verhongering het nie 'n invloed gehad op die predasietempo van M. muscaedomesticae nie. 'n Tegniek met Drosophila melanogaster Meig. as bron van prooi in die teling van C pumilio is suksesvol ontwikkel en dit kan van kommersiele waarde wees. Dit blyk dat D. melanogaster ideaal kan wees as 'n bron van prooi in die massateling van Cpumilio vanwee sy kort ontwikkkelingstyd van ongeveer tien dae. Die spesies is ook goedkoop en maklik om te teel, en het 'n baie hoe biotiese potensiaal.Care inops pumilio wat op 'n kunsmatige dieet gevoed het, het 'n verlengde ontwikkelingstyd en gewigstoename gehad, en het minder eiers gele as die wat op 'n natuurlike dieet gevoed het. C. pumilio het sy lewensloop op die kunsmatige dieet voltooi en beide die FJ en F2 generasies wat op die kunsmatige dieet gevoed het, was in staat om eiers te Ie. Dit kan die eerste stap wees in 'n poging om 'n kunsmatige dieet te vind wat dit sal moontlik maak om C. pumilio aaneenlopend te teel sodat dit deurlopend beskikbaar kan wees vir gebruik in die biologiese beheer van huisvliee,

Thesis (PhD) -- Stellenbosch University, 1989. / ENGLISH ABSTRACT: Arthropod communities of five proteaceous species viz. Protea repens. P. neriifolia. P.cynaroides, Leucospermum cordifolium and Leucadendron /aureolum were studied. A faunal list of the insects was compiled according to the feeding guilds of insects. Six phytophagous guilds were recognized: flower visitors, thrips, endophages, ectophages, sap-suckers, and ants. The guild composition, species packing and seasonal distribution for the free-IMng insects, spiders and other arthropods were investigated on the different plant species. The ants, flower visitors and sap-sucking species found on the plant species, were very similar, but the number of leaf chewing species common to all the plant species was low, suggesting that some species were monophagous. Insect abundance increased during the wet winter months when the plants were in flower. Of the total number of herbivores collected, flower visitors represented 69,5%, leaf feeders 14,5% and sap-suckers 16,1 %. The chewers constituted 60,1% of the total herbivore. biomass. Leaf damage increased with age ; young leaves were practically free of herbivore damage, while older leaves were stm acceptable as food. The degree of insect damage differed amongst the plant species varying from 2% to 15%. The following leaf characteristics were investigated to determine the factors involved in defence against insect herbivory : total phenolic content, protein precipitating ability, cyanogenesis, nitrogen content, leaf toughness, woodiness and fibre content lt appears that the plant species use different mechanisms to protect their leaves. The infructescences of Protea repens were exploited by the larvae of four Coleoptera and four Lepidoptera species. The community structure of these phytophagous insects was determined largely by negative interactions. Various strategies are followed (e.g. niche segregation in time and space) to lessen interspecific competition. / AFRIKAANSE OPSOMMING: 'n Studie van die arthropoocl gemeenskap op vyf proteasoorte, naamlik Protea repens. P. neriffolia. P. cynaroides. Leucospennum cordffolium en Leucadendron laureolum is gedoen. 'n Faunalys van insekte volgens hul voedingsgDdes is saamgestel. Die insekte is in ses fitofage gDdes verdeel naamlik blombesoekers, blaaspootjies, endovoeders, ektovoeders, sapsuiers en miere. Die samestelling van die gDdes, spesie-rangskikking en seisoenale verspreiding is bepaal vir die vrylewende insekte, spinnekoppe en ander arthropode. Die miere, blombesoekers en sapsuierspesies wat op die plantsoorte gevind is, is byna dieselfde, maar verslalle in die blaarvoederspesies is gevind wat 'n aanduiding is dat sommige spesies monofaag mag wees. Gedurende die nat wintermaande toon die insekgetalle 'n toename. Blombesoekers verteenwoordig 69,5%, blaarvoeders 14,5% en sapsuiers 16,1% van die aantal insekherbivore wat versamel is. Die kouers vorm 60,1% van die totale herbivoor biomassa Soos die blare verouder, neem die skade op die blare toe; jong blare toon byna geen skade nie, terwyl ouer blare steeds geskik is vir insekvoedsel. Die insekskade op die blare wissel by die verslallende plante tussen 2% en 15%. Om te bepaal watter blaareienskappe moontlik 'n rol kan speel in blaarverdediging teen insekte is die volgende ondersoek: totale fenoliese inhoud, die vermoe om proteiene te presipiteer, sianogenese. stikstofinhoud, blaartaaiheid, houtagtigheid en veselinhoud. Dit wil voorkom asof die plante verskillende meganismes gebruik om die blare te beskerm. Saadkoppe van Protea repens word deur vier Coleoptera en vier Lepidoptera spesies benut Die gemeenskapstruktuur van die boarders word tot 'n groat mate bepaal deur negatiewe interaksies. Verskeie strategiee word gevolg (bv. nissegregasie in ~ en ruimte) om kompetisie tussen spesies te verminder.

Thesis (MScConsEcol)--Stellenbosch University, 1970. / AFRIKAANSE OPSOMMING: Verskeie aspekte van die biologie van die wingerdfilloksera is bestudeer. Die ondergrondse lewensiklus is in spesiale teelbakke waargeneem en die ontwikkelingstydperk van elke stadium word afsonderlik aangegee. Dit is bepaal dat die ontwikkeling van n eier tot n volwasse radicicolae-wyfie gemiddeld 22 dae duur en dat die ontwikkeling van n eier tot n alata gemiddeld 30 dae duur. Die leeftyd en tydperk van eierlegging van n volwasse wyfie asook die aantal eiers wat geproduseer word, word aangegee. Verskillende gegewens wat in verband met oorwintering verkry is, word bespreek. Die tyd van voorkoms van die verskillende stadia van die radicicolae-siklus in die natuur, is bepaal. Die aktiewe · stadium duur vanaf September tot Mei, die oorwinterende stadium vanaf April tot Oktober en nimfe kom voor vanaf November tot April. Met die gegewens verkry, is die aantal generasies per jaar teoreties bepaal. Filloksera is tot op n diepte van 1.2 m in die grond gevind. Daar is vasgestel dat verskillende grondtipes n invloed op die fillokserabesmetting het. Die besmetting neem af soos die persentasie fyn plus medium sandinhoud van n grond styg. Opnames het getoon dat 95% van die wingerde met Jacquez as onderstok in die Stellenbosch-area besmet is en dat ongeveer 25% van alle wingerde in die Olifantsrivier-besproeiingsgebied besmet is. Met behulp van sekere vangapparate is alatae vir die eerste keer in Suid-Afrika in die natuur versamel. Die leeftyd en eierproduksie van alatae en verskillende aspekte van die voorkoms van die galicolae-siklus word bespreek. Twee metodes is toegepas om morfologiese rasse van filloksera·te onderskei. Met behulp van een van die metodes kon verskille tussen die populasies van die twee geografies verskillende areas wat ondersoek is, aangetoon word. / ENGLISH ABSTRACT: None

Thesis (MScAgric)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Colonies of Planococcus ficus (Signoret) were reared from three different areas, Hex River Valley, Robertson and Stellenbosch. An insectary colony and a table grape colony from Nietvoorbij experimental farm were also included in the study. A range of concentrations of chlorpyrifos was applied topically to individuals from the different colonies. The Stellenbosch population had the lowest LDso, although it was not significantly different from that of the insectary and Robertson colonies. The Hex River Valley and table grape colonies had a significantly higher LDso than the Robertson, Stellenbosch and insectary colonies, although the relative tolerance was 1.5, which would probably not result in significant control failure in the field. However, this does indicate that there is potential for the development of resistance to chlorpyrifos in the vine mealybug in South Africa. / AFRIKAANSE OPSOMMING: Kolonies van Planococcus ficus (Signoret), is versamel en geteel uit drie verskillende areas, Hex.riviervallei, Robertson en Stellenbosch. 'n Bestaande insektarium kolonie van die Lanbou Navorsings Raad en 'n tafeldruif kolonie vanaf Nietvoorbij proefplaas is ook ingesluit in die studie. 'n Reeks konsentrasies van chlorpyrifos is topikaal aangewend aan individue van die verskillende kolonies. Die Stellenbosch populasie het die laagste LDso getoon alhoewel dit nie betekenisvol verskil het van die LDso van die insektarium - en Robertson kolonies nie. Die Hexriviervallei en tafeldruif kolonies se LDso was betekenisvol hoër as die Robertson, Stellenbosch and insektarium kolonies. Alhoewel die relatiewe weerstand 1.5 was, sal dit waarskynlik nie tot 'n aansienlike beheermislukking in die veld lei nie. Nogtans dui dit op die potensiaal vir moontlike ontwikkeling van weerstand teen chlorpyrifos in die wingerdwitluis.

Dissertation (PhD(Agric))--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The codling moth, Cydia pomonella (L.) has been a major pest of pome fruits since before the turn of the last century. However, despite its high economic profile little is known about the bionomics and . behaviour of this pest in apple orchards in South Africa, information required for the development of a sustainable integrated management programme. In field trials there was contingency between the time of year and the upper and lower half of the tree. First generation moths laid significantly more eggs in the bottom half of the tree while second and third generation moths laid significantly more eggs in the top half of the tree. The preferred oviposition sites on Granny Smith (GS) and Golden Delicious (GD) cultivars, in order of preference, were leaves, fruit and wood. More eggs were laid on the fruit ofGS spurs (35.6 %) than on those ofGD spurs (10.7 %). On fruit spurs there was a significant increase in the number of eggs on GD leaves and GS fruit over the season, whereas the number of eggs on GS leaves and GD fruit remained constant. On branches there was an increase in the number of eggs on GD and GS leaves, but not on the fruit or wood. The preferred oviposition site on the fruit was the fovea of the stalk insertion and the rounded cheek area surrounding the fovea. The distribution within different fruit bearing classes (1 - 4 fruit per spur) was random only for one fruit per spur, while on the other spur classes clustering occurred. In laboratory studies of the embryonic and immature stages there was a linear relationship between rate of development and constant temperatures of 15, 17,20,25 and 30·C ± l·C. The lower threshold temperatures for embryonic, larval and pupal development were 11.1, 7.9, 9.9°C respectively. The degree-days required to complete embryonic, larval and pupal development were 80.5, 345, and 279 respectively. The response of the different stages to constant temperatures was similar to that under fluctuating temperatures. At temperatures below 16°C or abouve 27°C moths did not mate and few eggs were laid. Moth longevity decreased with increasing temperature. There was seasonal variation in longevity and oviposition at constant and fluctuating temperatures. Summer adults produced significantly more eggs than spring adults at constant temperatures. At a constant temperature of2S·C and fluctuating temperatures there were five distinct larval instars. The similarity between the mean head capsule width and ranges for each instar reared on fruit of different stages of development at fluctuating temperatures indicates that fruit development and temperature have little influence on mean head capsule width. From sleeve-cage studies in the orchard there was no significant difference in the fecundity of spring and summer moths. In the beginning of October spring moths produced significantly fewer eggs than in November. Egg mortality increased from 8.2 %in spring to 21.2 %in summer. Failure of 1st instar larvae to penetrate the fruit ranged from 4.9 % to 19.5 %, while mortality oflarvae from egg hatch to emergence from the fruit ranged from 29.7 % to 42.9 %. Mortality of 5th instar larvae after emerging from the apples ranged from 0 % to 8.7 % and pupal mortality from 0 % to 3.5 %. On large 27-year old trees more overwintering larvaewere found on Golden Delicious (13.9) than on Granny Smith trees (5.7), with over 70 % oflarvae being found in pruning wounds on both cultivars. On small 7-year old Golden Delicious and Granny Smith trees the mean number oflarvae was 0.5 and 2.0 per tree. A combined mating disruption and insecticide control programme reduced codling moth resistant populations to levels requiring a minimum to no insecticide intervention for several seasons. The efficacy of a pheromone based strategy, number of pheromone treatments, number of dispenserslha and level of insecticide intervention required are strongly influenced by prevailing weather conditions. Fruit infestation in orchards under a mating disruption programme and under an insecticide programme were greater along the borders compared to the interior. The presence of horticultural mineral oil on the leaves and branches did not have a detrimental effect on oviposition nor was there any significant ovicidal effect. A significant ovicidal effect was obtained when applied after oviposition. In field trials, insecticides with lower levels of efficacy than the primary insecticide, azinphos-methyl, provided acceptable control when successfully incorporated into a spray programme which followed a policy of alternation of insecticides across generations. The least variation in the number of degree-days between biofix and first egg hatch of the spring flight was when the second trap catch (Biofix 2) was used as the biofix. A biofix based on the first evening when the temperature reached or exceeded 1TC at 18:00 after first trap catch also showed less variation than when the biofix was based on first trap catch. The mean number of degree-days accumulated between Biofix 2 and first egg hatch was found to be 139.1 ° D. The number of degreedays between the first and second flight biofixes varied between 531.2 and 488.87°D with a mean of 508.1°D. / AFRIKAANSE OPSOMMING: Kodlingmot (Cydia pomonella) is reeds sedert die vorige eeu 'n sleutelplaag van kemvrugte. Ten spyte van die hoë ekonomiese profiel, is daar min kennis betreffende die bionomie en gedrag van hierdie plaag in appelboorde in Suid-Afrika. Hierdie inligting is noodsaaklik vir die ontwikkeling van 'n volhoubare geïntegreerde bestuursprogram. Tydens veldproewe is 'n korrelasie tussen die tyd van die jaar en eierlegging in die boonste of onderste helfte van bome gevind. Eerste-generasie motte het betekenisvol meer eiers in die onderste helfte van die bome gelê, terwyl tweede- en derde-generasie motte meer eiers in die boonste helfte van die bome gelê het. In toenemende volgorde was die voorkeur eierleggingsposisies op Granny Smith (GS) en Golden Delicious (GD) appels die blare, vrugte en hout. Meer eiers is op vrugte van GS spore (35.6%) as op dié van GD spore (10.7%) gelê. Op vrugspore was daar 'n betekenisvolle toename in aantal eiers op GD blare en GS vrugte deur die seisoen, terwyl die getal eiers op GS blare en GD vrugte konstant gebly het. Op takke was daar 'n toename in aantal eiers op GD en GS blare, maar nie op vrugte of hout nie. Die voorkeur eierleggingsposisie op vrugte was die fovea van die steelaanhegting en die wang rondom die fovea. Die verspreiding tussen verskillende vrugdraende klasse (1 - 4 vrugte per spoor) was slegs in die een-Vrug-per-spoorklas ewekansig, terwyl daar in die ander spoorklasse groepering voorgekom het. In laboratoriumstudies van embrioniese en onvolwasse stadia is 'n lineêre verband tussen ontwikkelingskoers en konstante temperature van 15, 17,20,25 en 30°C±I°C gevind. Die onderste drempel-temperature vir embrioniese, larwale en papie-ontwikkeling was onderskeidelik II. 1°C, 7.f?C en 9.9°C. Graaddae benodig vir voltooiing van embrioniese, larwale en papie-ontwikkeling was onderskeidelik 80.5,345 en 279. Die respons van verskillende stadia by konstante temperature het ooreengestem met hul respons onder wisselende temperature. Motte het nie gepaar nie en min eiers is gelê by temperature onder 16°C of bo 27°C. Die lewensverwagting van motte het afgeneem met toename in temperatuur. Seisoenale variasie in . lewensverwagting en eierlegging het voorgekom by konstante sowel as wisselende temperature. By konstante temperature het somer-volwassenes betekenisvol meer eiers as lente-volwassenes geproduseer. By 'n konstante temperatuur van 25°C, sowel as by wisselende temperature, het vyf duidelik onderskeibare larwale instars voorgekom. Die ooreenkoms tussen die gemiddelde kopkapsulewydte en wydte-reeks vir elke instar wat op vrugte van verskillende stadiums van ontwikkeling by wisselende temperature geteel is, dui daarop dat vrugontwikkeling en temperatuur weinig invloed op gemiddelde kopkapsule-wydte het. Tydens mou-hok studies in die boord is geen betekenisvolle verskil in die fekunditeit van lente- en somer-motte waargeneem nie. Vroeg in Oktober het lente-motte betekenisvol meer eiers as in November geproduseer. Eiermortaliteit het van 8.2% in die lente tot 21.2% in die somer toegeneem. Faling van 1ste instar larwes om vrugte te penetreer het van 4.9% tot 19.5% gewissel, terwyl mortaliteit van larwes vanaf uitbroei tot uitkoms uit die vrug van 29.7% tot 42.9% gewissel het. Mortaliteit van Sde instar larwes na uitkoms uit die vrug het van 0% tot 8.7% gewissel, en papie-mortaliteit van 0% tot 3.5%. Op groot, 27-jaar oue bome is meer oorwinterende larwes op Golden Delicious (13.9) as op Granny Smith (5.7) gevind, en meer as 70% van die larwes op beide kultivars is op snoeiwonde gevind. Op klein, 7-jaar oue bome was die gemiddelde aantallarwes op Golden Delicious en Granny Smithbome 0.5 en 2.0 onderskeidelik. 'n Gekombineerde paringsontwrigting- en insekdoder beheerprogram het weerstandbiedende kodlingmot-populasies verminder tot 'n vlak waar minimum tot geen insekdoder-toedienings vir verskeie seisoene gemaak is. Die effektiwiteit van 'n feromoon-gebaseerde strategie, aantal feromoonbehandelings, aantal vrystellers/ha en vlak van insekdoder-toediening word sterk deur heersende weersomstandighede beïnvloed. Die rande het hoër vruginfestasie as die middel getoon in boorde onder paringsontwrigting sowel as boorde onder insekdoder-programme. Die teenwoordigheid van minerale olie op blare en takke het geen nadelige effek op eierlegging gehad nie en dit het geen betekenisvolle eierdodende effek gehad nie. Indien die olie ná eierlegging toegedien is, is daar wel 'n betekenisvolle eierdodende effek waargeneem. Tydens veldproewe het insekdoders met laer effektiwiteit as die primêre insekdoder, azinfos-metiel, aanvaarbare beheer verskaf indien dit suksesvol geïnkorporeer is in 'n spuitprogram deur 'n beleid van afwisseling van insekdoders oor generasies. Die kleinste variasie tussen die aantal graaddae tussen biofix en eerste uitbroei van eiers is gevind indien die tweede lokvalvangs as biofix gebruik is. 'n Biofix gebaseer op die eerste aand na die eerste lokval vangste wat die temperatuur 17°Cofhoër was teen 18:00, het ook 'n kleiner variasie getoon as die eerste lokvalvangs. Die aantal graaddae tussen die tweede en derde vlug biofix het tussen 531.2 en 488.87°D gewissel, met 'n gemiddelde van 508.1°D.

Thesis (PhD (Agric))--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Biological control studies were conducted with isolates of entomopathogenic fungi Beauveria bassiana and Metarrhizium anisopliae from Ethiopia and South Africa against the spotted stem borer Chilo partellus. The study was conducted from April 2002 to April 2003, at the department of Entomology and Nematology, University of Stellenbosch, South Africa. The objectives were to screen these isolates for pathogenicity and to determine the susceptibility of different larval instars; to study the effect of temperature on fungal development and virulence; to investigate food consumption of fungus treated larvae; to determine compatibility of fungal isolates with insecticides; to study the effect of exposure methods and diets on larval mortality; and to evaluate promising isolates under greenhouse conditions using artificially infested maize plants. Four isolates of B. bassiana and six isolates of M. anisopliae were tested against second instar larvae. Of these isolates, B. bassiana (BB-01) and M. anisopliae (PPRC-4, PPRC-19, PPRC-61 and EE-01) were found to be highly pathogenic inducing 90 to 100 % mortality seven days after treatment. In subsequent assays, the fungal isolates were tested against third, fourth, fifth and sixth instar larvae. Second and sixth instar larvae were more susceptible to these isolates than third, fourth and fifth instar larvae. Conidial germination, radial growth and sporulation of the isolates PPRC-4, PPRC-19, PPRC-61, EE-01 and BB-01 were retarded at 15 and 35 0C. A suitable temperature range for the isolates was from 20 - 30 0C. At 25 and 30 0C the isolates induced 100 % mortality to second instar larvae within four to six days. Second and third instar C. partellus larvae were treated with the isolates PPRC-4 and BB-01, and daily consumption of maize leaf was measured. Treatment with the fungi was associated with a reduction in mean daily food consumption. In in-vitro studies, five concentrations (0.1 ppm, 1 ppm, 5 ppm, 10 ppm, and 100 ppm active ingredients) of the insecticides benfuracarb and endosulfan were tested with the isolates PPRC-4, PPRC-19, PPRC-16, EE-01 and BB-01. Increasing the concentration of the insecticides adversely affected germination, radial growth and sporulation of the isolates. In in-vivo studies combining the fungi, PPRC-4 and BB-01,with low concentrations (1 and 5 ppm a.i.), of the insecticides increased the mortality of third instar larvae from 65 to 100 %. Larvae sprayed directly with conidia, exposed to conidia treated leaves and dipped into conidial suspensions suffered high mortality of 98 to 100 %. Larvae exposed to treated leaves and larvae sprayed directly with conidia produced high numbers mycoses in cadavers. Exposure of larvae to treated leaves yielded high sporulation. At a low conidial concentration (1.25x107 conidia/ml), mycosis and sporulation were high. The optimum temperature was 20 0C for mycosis and 15 0C for sporulation. In greenhouse trails, a conidial suspension of 2 x 108 conidia/ml of the pathogenic isolates was sprayed on 3 to 4 week-old maize plants infested with 20 second instar larvae per plant. This resulted in suppression of foliar damage. Treatment with the fungi also reduced stem tunneling and deadheart. In addition, fungal treatment increased mean plant fresh and dry biomass compared to untreated control plants. In general, results from laboratory and greenhouse studies indicated that there was good potential for the use of these fungal isolates for controlling C. partellus larvae. / AFRIKAANSE OPSOMMING: Biologiese beheerstudies is uitgevoer met isolate van die insekpatogeniese swamme, Beauvaria bassiana en Metarrhizium anisopliae teen die gespikkelde stamboorder, Chilo partellus. Die doelwitte was om hierdie isolate te evalueer vir patogenesiteit; die vatbaarheid van verskillende larvale instars teenoor hulle te bepaal; die invloed van temperatuur op swamontwikkeling en virulensie te bepaal; die voedsel inname van swambehandelde larwes te ondersoek; die verenigbaarheid van die swamisolate met insektedoders te bepaal; die invloed van blootstellingsmetodes en diëte op larvale mortaliteit; en om belowende isolate in glashuisproewe te evalueer met gebruik van kunsmatig besmette mielieplante. Vier isolate van B. bassiana en ses isolate van M. anisopliae is teen tweede instar larwes getoets. Uit dié isolate is B. bassiana (BB-01) en M. anisopliae (PPRC-4, PPRC- 19, PPRC-16 en EE-01) as hoogs patogenies bevind. Hulle het 90 tot 100 % mortaliteit na sewe dae veroorsaak. In daaropvolgende essays, is die swamisolate teen derde, vierde, vyfde en sesde instar larwes getoets. Tweede en sesde instar larwes was gevoeliger vir die isolate as die derde, vierde en vyfde instar larwes. Spoorkeming, radiale groei en sporulasie van die isolate PPRC-4, PPRC-19, PPRC-61, EE-01 en BB-01, is by 15 en 35 0C vertraag. ‘n Aanvaarbare temperatuurreeks vir die isolate is vanaf 20 tot 30 0C. By 25 en 30 0C het die isolate 100 % mortaliteit teen tweede instar larwes binne vier tot ses dae geïndusseer. Tweede en derde instar C. partellus larwes is met die isolate PPRC-4 en BB-01 behandel en die daaglikse inname van mielieblare gemeet. Behandeling met die swamme is met ‘n afname in die gemiddelde voedselinname geassosieer In in-vitro studies is vyf konsentrasies (0.1 dpm, 1 dpm, 5 dpm, 10 dpm en 100 dpm aktiewe bestandele) van die insekdoders, benfuracarb en endosulfan getoets saam met die isolate PPRC-4, PPRC-19, PPRC-16, EE-01 en BB-01. ‘n Toename in die konsentrasie van die insekdoders het ontkieming, radiale groei en sporulasie van die isolate benadeel. In in-vitro studies het die kombinering van die die swamme, PPRC-4 en BB-01, met lae konsentrasies (1 en 5 dpm a.b.) van die insekdoders mortaliteit van derde instar larwes vanaf 65 tot 100 % laat toeneem. Larwes wat direk met spore gespuit is, aan behandelde blare blootgestel is en in spoorsuspensies gedoop is het tot hoë mortaliteit gelei, (98 tot 100 %). Blootstelling aan behandelde blare saam met ‘n lae konidiakonsentrasie, 1.25x106 spore/ml) en ‘n temperatuur van 15 tot 20 0C het tot hoë swammikose en sporulasie in kadawers gelei. In glashuisproewe, is ‘n spoorsuspensies van 2 x 108 spores/ml van die patogeniese isolate op 3 tot 4 weekoud mielieplante wat met 20 tweede instar larwes per plant besmet is gespuit. Dit het blaarskade onderdruk. Behandeling met die swamme het ook stamtonnels en dooiehart verminder. Boonop het swambehandeling die vars- en droë plantbiomassa laat toeneem in vergelyking met die onbehandelde kontrole plante. Oor die algemeen het resultate van laboratorium- en glashuisproewe getoon dat daar goeie potensiaal is vir die gebruik van hierdie swamisolate vir die beheer van C. partellus larwes.

Thesis (MSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Alien trees, Pinus spp. and Eucalyptus spp., affect ants negatively in the Cape Floristic Region (CFR), a global biodiversity hotspot in South Africa. They reduce ant abundance and species richness, thus also changing ant assemblage structure. This is alarming, because almost 1300 species of plant species in the CFR are dispersed by certain indigenous ants, and thus there is concern for an indirect effect on indigenous plant assemblages. One of the most impacting ant species on seed dispersal is the invasive Argentine ant (Linepithema humile (Mayr)), which discards seeds outside its nest, where they do not germinate. Ten sites, on Vergelegen Wine Estate, were selected to explore these effects of alien plants. These varied from invaded to non-invaded sites. Each site consisted of six sampling points, which in turn consisted of four pitfall traps left out for seven days, during December 2005, February 2006, May 2006 and September 2006. Forty species of ant were sampled, and various analyses used to illustrate the comparative effects of plant invasion. All analytical methods showed that invasive alien plants had a significant impact on the abundance and richness of the ant species assemblage, by creating a dense canopy cover that changed the abiotic environment of the epigaeic ants’ habitat. Furthermore, increased alien tree invasion correlated significantly with Argentine ant abundances. The Argentine ant displaced Pheidole capensis and Camponotus spp., while it decreased the abundances of commonly-occurring indigenous ants, such as Lepisiota capensis and Plagiolepis spp. Displacement by the Argentine ant may be a result of indirect competition for food resources. The effects of invasive aliens are synergistic in that there is a cascade effects from initial plant invasions to subsequent animal invasion. / AFRIKAANSE OPSOMMING: Indringer bome, Pinus en Eucalyptus, affekteer miere op negatiewe wyse in die Kaap Florsitiese Streek (KFR), ‘n area in Suid Afrika van belang t.o.v. globale biodiversiteit. Hierdie uitheemse indringer bome verminder hulle hoeveelheid en spesies rykheid. Die bogenoemde is kommerwekkend omdat meer as 1300 plant spesies in the KFR versprei word deur miere. Die verandering in hoeveelheid en versameling van inheemse miere kan dus ernstige implikasies hê op die saad verspreiding van inheemse plant spesies. Een van die mees verwoestende effekte op saad verspreiding is veroorsaak deur die indringer Argentynse mier (Linepithema humile (Mayr)), wat sade neer werp buite hulle neste, waar hulle nie suksesvol kan ontkiem nie. Tien monsterings-tereine was geselekteer om die bogenoemde effekte te ondersoek op Vergelegen Landgoed. Hierdie het afgewissel van indringer tot skoon tereine. Elke terrein is op ses versamelings-plekke gemonster, met vier pitvalle, wat oopgelê het vir sewe dae gedurende Desember 2005, Februarie 2006, Mei 2006 en September 2006. 40 spesies van miere was gemonster. Indringer plante het ‚n betekenisvolle impak gehad het op die hoeveelheid en rykheid van die mier gemeenskappe, deur die skepping van ‚n dig baldakyn wat die abiotiese omgewing van die miere se habitat verander het. Die vermeerdering van indringer plante veroorsaak die vermeerdering van Argentyne miere. Kanonieke Mede-Respons Analise illustreer dat die Argentynse mier Pheidole capensis en Camponotus spp. verplaas het, terwyl dit ander inheemse mier getalle verminder het, soos Lepisiota capensis en Plagiolepis spp. Die verplasing deur die Argentynse mier mag die resultaat wees van indirekte wedywering vir hulpbronne. Die effekte van indringer species is dus sinergisties deur dat ‚n kaskade effek ontstaan vanaf plant tot dier indringer spesies.