The irrigation farming methods on the Makhathini Flats are thought to be responsible for recent increase in malaria cases in the Mamfene area of northern KwaZulu-Natal despite ongoing malaria control activities. Their coincidence with the period of intensive fanning is an interesting one. This study was therefore carried out to determine the relationship between larval habitats and adult mosquito population in malaria transmission using Geographic Information System (GIS). Four types of breeding sites were utilised by malaria vectors in Mamfene, viz; types 1, II, III and IV. Habitat type I was tap pools, type II was irrigation spillage in agricultural land, type III was spillage outside but adjacent to the agricultural land and type IV was depression pools located both in the Balamhlanga swamp and inland. The cumulative larval density in all habitats peaked in March 1995 (20/man-hr), with irrigation spillage (type III) recording the highest density index (33/man-hr) as compared to tap pools (type I) which recorded 32.8/man-hr while other waterbodies recorded I3 .4/man-hr (type II) and O.5/man-hr (type IV) respectively. Subsamples of both larvae and adults of An. gambiae group were identified by the Polymerase Chain Reaction (PCR) technique. Of the larvae identified, 94.1 % and 5.9% (n=289) were An. arabiensis and An. quadriannulatus respectively while in the adult component, the composition was 98.7% and 1.3% (n=303) for An. arabiensis and An. quadriannulatus respectively. This confirmed An. arabiensis as the dominant malaria vector in Mamfene area while the exophilic behaviour of An. quadriannulatus was portrayed. Of the An. gambiae group dissected for parity, 51 .5%) were found parous. This is an indication that the population was old and was able to maintain transmission locally despite ongoing vector control measures. The Global Positioning System (GPS) was used to position larval and adult mosquito sampling sites. The spatial distribution of adult mosquitoes from the breeding sites were plotted using GIS soft ware (Map Info ) and the distance between the breeding sites and study houses were measured using a utility distance tool. With the aid of GIS, the adult mosquito density in houses could be used as an indicator to locate the breeding sites in the vicinity. The importance of these findings in terms of application in cost-effective malaria control cannot be over-emphasized. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Niche and life-history differences in five species of Trithemis were investigated to determine the extent of interspecific competition. Interspecific competition was mostly avoided because species favoured different habitats and microhabitats. There was the possibility of competition between larvae under conditions of lowered food concentration, where they occurred in the same habitat and microhabitat. Larvae of different species preferred specific prey taxa, but chose to feed on a different prey taxon once it was more readily available. Because species were restricted more by food size than taxon, competition for food was unlikely. Interspecific competition may have occurred between adults because the niche breadth of some species became contracted as the density of other species increased. Interspecific competition among larvae was unlikely because individuals of different sizes were present together, allowing for food partitioning. Asynchronous development therefore ensured that competition for food of the same size was reduced. Competition was also reduced by species showing peaks in abundance at different times of the year. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Extensive seasonal collections along with absolute counts of all the arthropods attracted to medium- and large mammal carcasses resulted in the most complete record of carrion-fauna in Africa to date. The abundance of these species and their seasonal, successional, and diel patterns of carcass-attendance are discussed. More than 98% of species were insects and their presence at the carcass habitat could be classified as obligate, opportunistic, or incidental. A recognisable community of carrion-associated arthropods consistently attracted to the carcass habitat is described, comprising sarcophages, coprophages, keratophages, detritivores, predators and parasites. The interactions and functional ecology of these arthropods is described. The blow-flies Chrysomyia albiceps (Wd.) and C. marginalis (Wd.) were found to be pivotal or key species due to the impact of their larvae on carcass decomposition and their influence on other members of the community. In view of the importance of these blow-flies, their abundance, and the potential role of the adults as dispersal agents of disease organisms, studies were performed to clarify the population dynamics of the two species. The biology and ecology of the immature stages is discussed, including such aspects as the availability of mammal carcasses for oviposition and larval development, and mortality of larvae in the digestive tracts of vultures. By feeding a radioactive isotope of phosphorous (p[32]) to a reared population of adult flies, the dispersal and flight ranges, habitat preferences and population densities of both blow-fly species were studied. The seasonal abundance of C albiceps, C. marginalis, and Lucilia spp. was monitored by monthly trapping at three sites in the study area. Further studies using radioactively-marked blood in a carcass under natural conditions revealed that the distribution of flyspecks deposited by blow-flies is largely dependent upon vegetational structure in the immediate vicinity of the carcass, and the majority of such droplets occurred near the carcass between one and three metres above ground. A distinction in fly-specks was made between vomit droplets, faecal droplets, and the newly tenned discard droplets. The feeding behaviour of C. albiceps and C. marginalis is discussed with reference to the transmission of anthrax in the northern K.N.P. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1984.

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.

The Karkloof blue butt erfly, Orachrysops ariadne (Butler), is endemic to the Mistbelt grassland of KwaZulu-Natal province, South Africa, and is currently Red-listed as 'Vulnerable' . O. ariadne is univoltine and on the wing in March and April, when it utilizes eight species of nectar plants. This study confirmed that the larval hostplant is Indigofera woodii H. Bol. var. laxa H. Bol., an erect variety. It was also confirmed that this butterfly is ant-dependent, with the young larva being taken into the nest of Camponotus natalensis (F. Smith) where development continues, including pupation. This study compares the ecological conditions at the four known locations so as to make informed decision s regarding its conservation. A large proportion of the grassland in KwaZulu-Natal has been aforested and cultivated, and at least 92% of the Mistbelt has been transformed, with only about 1% in good condition remaining. Predictions on the habitat and habit at requirements of this species are necessary for developing a conservation strategy and action plan. Here , we propose O. ariadne as an indicator species for Mistbelt grass land. Saving enough of the remaining Mistbelt grassland is crucial, not just for the survival of the Karkloof blue, O. ariadne, but also for the Mistbelt grassland community as a whole. The population structure and movement of Orachrysops ariadne and O. subravus were studied by mark-release-recapture methods in 1999. There were 290 O. ariadne marked over 48 days between March and April, 124 (42 .8%) were recaptured at least once. Of 631 O. subravus marked over two months between September and November, 311 (49 .3%) were recaptured at least once. Both species exhibited protandry, male appearance about one to two weeks earlier. The sex ratio of O. ariadne is heavily male biased 5.6 :1 (246 males and 44 females), and the sex ratio of O. subravus is 1.6:1 (387 males and 244 females). The Jolly-Seber model was used to estimate daily population numbers (N ᵢ), survival rates (Ø ᵢ), recruitment rates (B ᵢ), proportion of marked animals in the total population (α ᵢ ), and the number of marked animals at risk (M ᵢ) . Average residence times of male adults were generally similar in both species in the range of 5.36-5.44 days, and were slightly longer for male than for female O. subravus (by 4.09 days). 0. ariadne is a strong and rapid back and forth flier, covering mean recapture distances of 157 m, almost twice that of 0. subravus, principally in search of scarce nectar sources. The extreme rarity of 0. ariadne is not so much to do with behaviour, survivorship or longevity, but rather the butterfly is limited in distribution by suitable habitat for both larva and adult. The aim of management is to optimize the habitat so that it best meets the present and future needs of the butterfly. The effects of the current fire regime on the butterfly, host plant and ant host were evaluated here. It is recommended that burning only take place after the larvae have hatch ed and gone underground with the ant host. Using GPS and GIS, core, quality habitat characteristics were defined. In cooperation with the landowner at one site, alien invasive plants are being removed to increase the area of quality habitat. Availability of host plants is limiting for success of the butterfly in the field. Guidelines are provided for propagation and introduction of the host plant, so as to provide the butterfly with more oviposition sites. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.

No abstract available. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

This study investigated the prevalences and intensity of intestinal parasites and aspects of their epidemiology among children in the Qwa-Qwa region of the eastern Free St~te. Faecal samples of 1180 children differing socio-economic status from nine schools at altitudes varying from 1660m to 2200m were examined quantitatively by means of the formol-ether sedimentation technique. Socio-economic, and demographic characteristics for the communities served by the schools were obtained from the literature and from a questionnaire. The study showed that, the area supports a markedly low diversity of parasite infections, and at lower intensities, than low altitude areas such as the coastal plain of KwaZulu-Natal and Eastern Cape, the Northern Province, Mpumalanga and the Western Cape. The intestinal parasite fauna affecting children in Qwa-Qwa is dominated by protozoans with only few helminths and no hookworm or bilharzia. The results indicated that factors which influence the transmission of intestinal parasites in Qwa-Qwa appear to be related primarily to social, economic and cultural aspects of the peoples' lifestyles. Climatic factors were not found important. There was a significant seasonal effect on the intensities of all parasite infection, except two protozoans, Entamoeba coli and Endolimax nana. Water source, electricity, house-type and quality of meat were found to be the important socio-economic factors that influenced parasite transmission. These relationships were investigated by fitting logistic regression and generalized linear mixed models. By documenting human parasitism (above 1700m) this study provided an endpoint to the altitudinal transect conducted in 1993 in KwaZulu-Natal by Appleton and Gouws (in press). Public health authorities and Primary Health Care personnel should find this study useful when designing and implementing nutrition and parasite control. Severe ascariasis has been reported from the study area. It will help focus PHC activities in Qwa-Qwa and in the wider context of Free State Province by demonstrating the value of proper personal and environmental hygiene in the home, thereby forming the basis for intestinal parasite control at the community level. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Scarabaeid pests in South Africa and especially KwaZulu-Natal are characterised by a very long larval life cycle and short pupal and adult periods. However, it has nearly always been the adults of the species that have been identified, with very little attention paid to the larval identification of the species. This is unfortunate as it is nearly always the larval stage that is found to be associated with crop damage. Accurate identification of the species of these larvae is important for the management of scarabaeid pest species, as it unlocks the necessary information on the biology and ecology of many species, which allows the adaptation of control methods for different species. Inadequate keys for the taxonomy of larvae of these groups, as well as the lack of morphological taxonomists working on these groups have been identified as constraints. When a species is difficult to identify using traditional taxonomic methods, DNA diagnostic tools can be useful. Chapter 2 investigated the feasibility of identifying scarabaeid larvae using mitochondrial DNA data. Variation in the base pair sequence of the mitochondrial cytochrome c oxidase sub unit I (cox 1) gene was used. DNA sequences of cox 1 from scarabaeid larvae collected from sugarcane fields were compared with sequences from scarabaeid adults of known species in order to identify the species attacking sugarcane. Neighbour-joining and maximum parsimony analyses of 658 bp cox 1 sequences identified groups of larvae that linked to adult specimens. The major groupings delimited specimens belonging to the subfamilies Dynastinae, Melolonthinae and Rutelinae. Within-group sequence divergence ranged from 0 - 3.4 % and divergence between sister groups ranged from 2.6 - 25.1 %. The recorded divergence range within and between tribes was 0 - 21.3 % and 17.3 - 28.5% respectively. Similarly, the divergence range observed within and between genera was 0 - 19.2 % and 17.1 - 25.4% respectively. The maximum sequence divergence observed within subfamilies was 23.7 % and divergence between subfamilies ranged from 16.8 - 26.7 %. Examination of pairwise sequence divergence levels as well as node support allowed 68% of the unidentified larval specimens to be associated with identified adult specimens. Phylogenetic analysis matched identified adult mtDNA with unidentified larval mtDNA. This allowed the identification of those larvae through morphological characteristics unique to certain species. To create a field key to the subfamilies of Dynastinae, Melolonthinae and Rutelinae the most useful character distinguishing larvae of different species was the raster but additional morphological characteristics were included. These relationships between larval and adult scarabaeid specimens from sugarcane were examined using various phylogenetic tools. The data set included a total of 19 morphological characters as well as 166 partial cox 1 gene sequences. Maximum parsimony analyses were performed on morphological, molecular and combined data. The same morphological and molecular data sets were run both separately and as a combined analysis with MrBayes. In both types of analyses the morphological data performed poorly and crude groupings resulted, dividing taxa to tribe level only. Molecular data showed greater resolution than the morphological data and taxa were separated into groups equivalent to species and morphospecies designated in Chapter 2. A partition homogeneity test indicated that both data types could be combined. It is recommended that both morphological and molecular data be utilised in identification of scarabaeid sugarcane pests and that a character-based approach be implemented. Further molecular data from other genes should be included to test the accuracy of these results. The keys produced during this study will allow workers to focus on a single species biology, and subsequently allow an analysis of between species interactions, and within species control. These advances are a start to the improvement of knowledge of the species composition of scarabaeid larvae in sugarcane fields, thus making management and biological control of these pests a greater possibility. Further recommendations for future work are discussed in Chapter 5. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

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.

The South African grassland biome is disappearing rapidly through advancing development and change in agricultural land use. One of the most threatened grassland types, Midlands Mistbelt, in the KwaZulu-Natal Midlands is an extremely diverse and home to many endemic species across an array of taxa. Three taxa, namely, grasses, grasshoppers and butterflies represent various trophic levels, which are important to the functioning of the grasslands. Ten grasslands were sampled by walking ten fifty metre transects for a twelve-month period. The grasslands were selected as they represented a range of management practices and varying environmental conditions. Using Indicator Species Analysis (ISA) twenty-two species of grasshopper were identified as indicators of environmental variables and management practices. The abundances of the various species indicated the intensity of the management regimes or disturbances. Using the twenty-two grasshopper species abundances and a three hundred point sampling assessment of the grasses creates an assessment tool that can rapidly appraise the management of the grassland, but due to lack of data for other taxa, cannot assess whether management practices for the focal taxa create congruent results for non-focal taxa. Two of the three taxa proved to be good indicators of grassland health, whilst the third, butterflies were ineffectual, due to low abundance and richness. From the results it was concluded that burning was taking place to frequently, and required a reduction to every four years, as this would improve butterfly richness and abundance, and increase abundance of endemic and flightless grasshopper speCies. A rotational grazing system needs to be implemented at sites where continual grazing takes place, wildlife or livestock, impacts on the grassland condition and species diversity. Increasing habitat heterogeneity increases species diversity, and allows later successional species to be included in the grasshopper assemblage. Management of the grasslands in the KwaZulu-Natal Midlands needs to be more responsive and adaptive. In addition, small fragment management needs to be intensified to provide a range of habitats and refugia that will suit all species. This study advocates the use of grasshoppers and grasses as suitable biotic indicators of grasslands in the KwaZuluNatal Midlands. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2005