Often perceived as pests, pigeon control is applied without investigating environmental, ecological and anthropogenic factors which affect their populations and response to controls. Estate Management of the University of South Africa’s Muckleneuk campus identified a need to investigate and address a perceived pigeon problem. Staff perceptions regarding the presence and attitude towards control of the pigeons was undertaken through an online Survey Monkey questionnaire and semi- structured interviews until saturation was achieved. It was determined that the a s sumed negative perception towards the pigeons was in fact incorrect. Participants would rather encourage the nesting and breeding activities of pigeons on campus, as they felt that the human–pigeon interactions and viewing of squabs in nests contributed positively to their work environment. Participants did not consider the pigeons or their related activities to pose a problem. It was felt that should control be imposed, the birds should rather be humanely managed through non-lethal measures rather than eradication. Pigeon numbers on five buildings on the University’s campus were counted at dawn and dusk, every week, for two years. The first year provided baseline data and the second year was when control measures were applied. The study determined that the pigeon population index fluctuated seasonally while breeding occurred throughout the year, with notable peaks and declines relating to physiological and population dynamics. The pigeons seemed to make opportunistic use of crop availability in surrounding farmlands during optimal production periods, while conserving energy when not favourable. Site selection in relation to building aspect indicated significant differences in all the seasons except for winter, while a positive significant relationship between level height and pigeon number was recorded. Once the control measures were applied, the total pigeon index on the campus declined by 50%. Control structures differed significantly in efficacy. Bird spikes indicated the highest efficacy at reducing the pigeon population index and seasonality did influence this efficiency. Birds of prey and an audio bird scarer were used to compare actual versus implied predator presence, it was determined that there was an association between method of scaring and the number of pigeons observed on the different time periods. Pigeons were observed to continue the natural trend of dispersion and return at the dawn and dusk counts during the audio bird scarer trial without being actively discouraged or dislodged from the building. Pigeons reacted positively to the visual raptor presence, which caused them to take flight from the buildings. The visual effect was only temporary however as pigeons returned once the threat had been removed 10 minutes post scare. The studies concluded in an interdisciplinary management plan presented to the University Estates. / Environmental Science / M. Sc. (Environmental Science)

This study assessed the mycological and aflatoxin contamination of peanuts collected from Kinshasa, DRC and Pretoria, South Africa. Forty peanut samples were collected randomly at informal markets in the two cities and analysed for mycoflora and aflatoxins (B1, B2, G1 and G2) using standard methods. The results indicated that 95% and 100% of peanut samples collected from Kinshasa and Pretoria, respectively were contaminated with aflatoxigenic fungi with Kinshasa’s samples being the most contaminated (up to 49, 000 CFU/g). Seventy percent (70 %) of Kinshasa-samples and 35% of Pretoria-samples exceeded the maximum allowable limit of aflatoxin B1 set by JECFA (5 ppb). Statistical evidence showed a significant positive correlation between mycoflora and aflatoxin level for Kinshasa-samples (r = 0.4743, p < 0.005) while Pretoria-samples showed no correlation. The study reveals that high level of contamination in Kinshasa-samples could be due to the tropical nature of the climate and poor storage conditions as compared to Pretoria which is sub-tropical and sanitary regulations are enforced. / Life and Consumer Sciences / M. Sc. (Life Sciences)

The objective of this research was to investigate the occurrence of mycoflora in rice plants and rice seeds in South Africa and their negative impact. A total of six species of Fusarium were isolated from diseased rice plants and rice seeds and identified as F. anthophilum, F. chlamydosporum, F. compactum, F. equiseti, F. fujikuroi and F. semitectum. In the translation elongation factor data set, Fusarium equiseti isolates grouped together within the F. incarnatum - equiseti Species Complex (FIESC). The isolates from rice clustered together in a single clade with the F. equiseti and F. incarnatum isolates forming two separate sub-clades.The isolates of F. equiseti present a new phylogenetically distinct species in FIESC. In the pathogenicity tests, isolates of both F. anthophilum and F. fujikuroi caused bakanae disease to rice plants. Fifty four rice cultivars and lines were tested by the standardized test tube inoculation method for resistance and susceptibility against bakanae isolate of F. anthophilum and the bakanae isolate of F. fujikuroi. None of the rice cultivars and lines was found to be resistant to bakanae isolates of Fusarium spp. The fungicide, benomyl was found to be most effective as a seed treatment for controlling bakanae disease of rice due to isolates of both F. anthophilum and F. fujikuroi. Thiram was found to be the least effective fungicide for controlling bakanae disease of rice caused by isolates of both the Fusarium spp. Apart from Fusarium species, other fungi that were also isolated from diseased rice plants and rice seeds were identified as Alternaria alternata, Alternaria longipes, Cochliobolus miyabeanus, Nigrospora sphaerica, Phoma eupyrena, Phoma jolyana, Phoma sorghina and Pithomyces sp. In mycotoxin tests, the isolates of both F. anthophilum and F. fujikuroi produced moniliformin. None of the isolates of F. anthophilum and F. fujikuroi produced fumonisins. This research is important as it identifies many fungal species in rice plants and seeds in South Africa for the first time. Currently, there is very little literature that makes reference to such findings under South African conditions. In addition, this investigation unravels previously unknown information on the resistance of rice to bakanese disease. Finally, information is provided on the effectiveness of commonly used fungicides (benomyl and thiram) to control rice diseases. This knowledge is crucial information that is useful to plant pathologists, the farming community and the scientists that are involved in strategies of fighting or reducing rice diseases so as to help contribute to food security. / Environmental Sciences / D. Phil. (Environmental Science)

MSc (Zoology) / Department of Zoology / See the attached abstract below

Genetically modified (GM) white and yellow maize, Zea mays, has been commercially released and cultivated in South Africa since 1997/1998. The traits expressed are insect resistance and herbicide tolerance conferred by the bacteria Bacillus thuringiensis (Bt) Cry genes and Agrobacterium 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase gene, respectively. The Cry genes have been used widely to control lepidopteran insect pests but insect resistance to GM Bt crops has been a concern since the introduction of this technology. A management strategy includes refugia planting of 5% non-Bt plants, with no insecticide application, and 20%, where insecticide application is allowed. These refugia are designed to allow the survival of insect pests within restricted planted zones. However, in South Africa there are reports of Bt-resistant stem borer (Busseola fusca) (Fuller) (Lepidoptera: Noctuidae) and non-compliance with refuge planting. The aims of this study were two-fold: 1. To conduct a survey among KwaZulu-Natal (KZN) GM maize growers to ascertain information such as level of compliance with refuge planting and to determine which refugia were predominantly planted and reasons thereof; 2. To conduct a replicated field trial to determine yield, insect borer damage and economic benefit of the 5% unsprayed and 20% sprayed refuge options (including three configurations namely strip, perimeter and block and a 5 and 20% ‘refuge-in-a-bag’ option). The survey indicated that 28 out of 29 (96.6%) KZN Bt maize growers plant the 5% non-sprayed refuge with 27 (96.4%) of those respondents planting the strip configuration for the purpose of insect management (75%) and ease of planting (32.2%). The survey also showed that 7 (seven) i.e. 21.9% of KZN Bt maize growers observed borer damage and although growers are now fully compliant with refugia planting requirements, initially 7 respondents (24.1%) did not comply with or plant refugia correctly. Furthermore, 7 respondents reported insect borer damage in their maize with 4 of the 7 instances (57.1%) likely stemming from incorrectly planted refugia. vii No significant differences in yield or insect damage were observed between the 5 and 20% refugia for any of the planting configurations in the field trial. However due to costs involved with insecticide application and labour required for the operation in the 20% option, these treatments were less economically advantageous than the non-Bt control. The 20% block and strip configurations had a cost benefit ratio of ZAR 7.21 and ZAR 6.67 respectively, earned per R1 spent by the grower compared with ZAR 7.76 in the sprayed control. The cost-benefit comparison for the 5% block and strip configurations was ZAR 8.48 and ZAR 7.71, respectively compared with ZAR 9.44 in the unsprayed control. In addition, the 20% seed mixture limited borer damage to 4.95% when compared with 15.77% damage in the sprayed control (ANOVA, F pr = 0.124). The seed mixtures are not available commercially and the results from the survey indicated that some education and marketing by the seed companies would be advisable prior to their release to the farming community. In order to determine which of the refuge options between 5 and 20% would be more advantageous for growers overall, regardless of the planting configuration; data were grouped and analysed. There were no significant differences in either the yield or insect damage for the 5 and 20% refugia, but the cost-benefit calculations indicated that the 5% option was more cost effective – for the 5 and 20% refugia, ZAR 7.97 and ZAR 7.15 respectively, earned per ZAR 1 spent by the grower (ANOVA, F pr. = 0.03). This is because no insecticide was used in the 5% treatments. Mean ear damage comparisons between the 5 and 20% refugia showed that the 20% refuge in the perimeter configuration incurred the least damage (2.65% ear damage) compared with 5% perimeter (10.86% ear damage), although the reasons for this are not clear. While the results of the field trials showed no significant differences in insect damage and yield with regard to choice of refuge configuration, monitoring insect resistance management remains an integral part of Bt maize crops in South Africa, in order to delay further resistance development and to prolong the viability of Bt technology. / Agriculture and  Animal Health / M. Sc. (Agriculture)

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.

Abstract not available. / Thesis (Ph.D)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Soybeans, Glycine max, are an economically and strategically important crop in South Africa (SA). In order to meet local demands, large imports of soybeans are required, e.g., in the 2005/2006 soybean production period, 842 107 tonnes of oilcake were imported. Due to an increase in soybean production throughout the world, diseases that affect this crop have also increased in incidence and severity. Sclerotinia sclerotiorum, the causal organism of sclerotinia stem rot (SSR), is an important yield limiting disease of soybeans, as well as numerous other crops. The pathogen was first reported in SA in 1979. However, it was only in 2002 that this fungus was considered a major pathogen of soybeans in SA. The research reported in this thesis was conducted to investigate the epidemiology of S. sclerotiorum and examine numerous potential control methods for this pathogen, i.e., resistant cultivars, biocontrol, chemical control and seed treatments. A S. sclerotiorum isolate was obtained from sunflowers in Delmas, Mpumulanga, SA, in the form of sclerotia. This isolate was cultured and sent for identification and deposition in the Plant Protection Research Institute collection. This isolate, in the form of mycelia, was used for the duration of the study. For epidemiology studies, the effect of temperature, leaf wetness duration (LWD) and relative humidity (RH) were examined for their effect on rate of pathogen development. Twenty four combinations of temperature (19°C, 22°C, 25°C and 28°C), LWD (24, 48 and 72 hr) and RH (85 and 95%) were investigated. No interaction between temperature, LWD and RH was found. Temperature alone was the only factor that affected disease development. At 22°C, the rate of pathogen development (0.45 per unit per day) was significantly higher than all other temperatures, indicating that this temperature is optimum for disease development. Thirteen different soybean cultivars, i.e., LS6626RR, LS6710RR, LS666RR, LS555RR, LS6514RR, LS678RR, Prima 2000, Pan 626, AG5601RR, AG5409RR, 95B33, 95B53 and 96B01B, commercially grown in SA were investigated for their reaction to S. sclerotiorum. Prima 2000, 96B01B, 95B33 and AG5409RR were considered to be the least susceptible as they showed a significantly low rate of pathogen development (0.28, 0.28, 0.24, 0.23 per unit per day, respectively) and produced a significantly low number of sclerotia (3.03, 3.42, 3.21, 2.38, respectively). LS6626R and LS666RR may be considered most susceptible because of their significantly high rate of pathogen development (0.45 and 0.42 per unit per day, respectively) and high sclerotia production (8.16 and 7.50, respectively). Regression analysis showed a positive correlation coefficient (R2=0.71) between rate of growth of the pathogen and number of sclerotia produced, indicating that a higher rate is associated with a higher number of sclerotia. In vitro dual culture bioassays were performed to identify the biocontrol mechanisms of the biocontrol agents, EcoT® (a seed treatment) and Eco77® (a foliar treatment), against hyphae and sclerotia of S. sclerotiorum. Ultrastructural studies revealed that mycoparasitism is the probable mode of action as initial signs of hyphae of EcoT® and Eco77® coiling around hyphae of S. sclerotiorum were observed. Surface colonization of sclerotia by hyphae of EcoT® and Eco77® was also observed. In vitro antagonism of EcoT® against S. sclerotiorum on soybean seed was performed to determine pre-emergence and post-emergence disease. There was no significant difference in percentage germination between seeds treated with EcoT® and plated with the pathogen, untreated seeds and no S. sclerotiorum, and the control (i.e. no EcoT® and no pathogen). However, percentage non infected seedlings from seeds not treated with EcoT® was significantly lower, suggesting that EcoT® may be successfully used as a seed treatment for the control of SSR. In vivo trials were performed to investigate the effect of silicon (Si) alone, and in combination with Eco77®, on the effect of the rate of disease development. Plants treated with Eco77® had a significantly lower rate of disease development (0.19 per unit per day for plants treated with Eco77® and S. sclerotiorum and 0.20 per unit per day for plants treated with Eco77®, S. sclerotiorum and Si), compared to plants not treated with Eco77® (0.29 per unit per day for plants treated with S. sclerotiorum and 0.30 per unit per day for plants treated with S. sclerotiorum and Si), regardless of the application of Si. Similarly, plants treated with Eco77® had a significantly lower number of sclerotia (0.46 for plants treated with Eco77® and S. sclerotiorum and 0.91 for plants treated with Eco77®, S. sclerotiorum and Si), compared to plants not treated with Eco77® (3.31 for plants treated with S. sclerotiorum and 3.64 for plants treated with S. sclerotiorum and Si). The significantly lower rate of disease development coupled with a significant reduction in sclerotia showed that Eco77®, and not Si, was responsible for reducing the severity of SSR. A strong positive correlation between rate of disease development and the number of sclerotia produced (R2=0.79) was observed. For the investigation of various fungicides for the control of S. sclerotiorum, in vitro trials to determine the potential of three different fungicides at different rates, i.e., BAS 516 04F (133 g a.i. ha-1), BAS 516 04F (266 g a.i. ha-1), BAS 512 06F (380 g a.i. ha-1) and Sumisclex (760 g a.i. ha-1) were initially conducted. The control (non-amended PDA) had a significantly higher area under mycelial growth curve (243.0) than all fungicides tested. BAS 516 04F (at both concentrations) and BAS 512 06F completely inhibited the mycelial growth of S. sclerotiorum. Sumisclex inhibited the fungus by 89.07%. For in vivo trials, preventative treatments, i.e., BAS 516 04F (133 g a.i. ha-1), BAS 516 04F (266 g a.i. ha-1), BAS 512 06F (380 g a.i. ha-1), curative treatment, i.e. Sumisclex (760 g a.i. ha-1) and a combination preventative/curative treatment, i.e., BAS 512 06F (380 g a.i. ha-1)/Sumisclex (570 g a.i. ha-1) were investigated. No significant difference in disease severity index (DSI) was found between fungicide treatments and the inoculated control. BAS 512 06F and BAS 512 06F/Sumisclex had significantly lower grain yields (6.09 g and 5.96 g, respectively) compared to all other treatments. There was a positive correlation coefficient (R2=0.76), between DSI and grain yield, indicating that a high DSI is correlated with low grain yield. Trials to evaluate the effect of commercially available and currently unregistered seed treatments for the control of S. sclerotiorum on soybean seeds in vivo and in vitro were performed. Seed germination tests were performed to determine if seed treatments had any negative effects on seed germination in vitro. All seed treatments tested, i.e., BAS 516 03F (8, 16 and 32 ml a.i. 100 kg-1 seed), BAS 512 00F (7.5, 15 and 32 ml a.i. 100 kg-1 seed), Celest XL (100, 125, 200 and 250 ml a.i. 100 kg-1 seed), Sumisclex (5 and 10 ml a.i. 100 kg-1 seed), Benomyl (150 g a.i. 100 kg-1 seed), Captan (240 ml a.i. 100 kg-1 seed), Thiulin (180 g a.i. 100 kg-1 seed) and Anchor Red (300 ml a.i. 100 kg-1 seed), showed no negative effect on seed germination. For in vivo trials, BAS 516 03F (16 and 32 ml a.i. 100 kg-1 seed), BAS 512 00F (7.5, 15 and 32 ml a.i. 100 kg-1 seed), Celest XL (100, 125, 200 and 250 ml a.i. 100 kg-1 seed), Sumisclex (5 and 10 ml a.i. 100 kg-1 seed), Benomyl and Anchor Red had significantly similar percent germination and percent seedling survival as the untreated/uninoculated control. These seed treatments should be recommended for the control of S. sclerotiorum, as they protected seed during germination and subsequent seedling development. BAS 516 03F (8 ml a.i. 100 kg-1 seed) should not be recommended for the control of SSR, as it gave the lowest percent germination and percent seedling survival. The results presented in this thesis have helped to identify optimal environmental conditions for the development of S. sclerotiorum, which is important for the development of forecasting models for disease control. The least and most susceptible cultivars of those tested have been identified. Biocontrol using Eco77® as a foliar application showed great potential. The effect of Si needs to be further investigated, including the testing of more frequent applications and higher concentrations. The fungicides tested in this research did not show any potential for the control of SSR. However, the spray programme tested is for the control of soybean rust (Phakopsora pachyrhizi), and was investigated for its potential for the control of SSR. The spray programme, fungicide application and rating scale needs to be modified, to determine the true potential of these fungicides for the control of SSR. Numerous seed treatments have shown potential for the control of seed infection by SSR. Due to difficulties in producing ascospores, which are the primary source of inoculum for this pathogen in the field, all studies in this research were conducted with mycelia and not ascospores. The production, collection and storage of ascospores needs to be thoroughly investigated, and research conducted with ascospores. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

In the KwaZulu-Natal (KZN) Midlands North region of South Africa, the importance and increased prevalence of endemic scarabaeids, particularly Hypopholis sommeri Burmeister and Schizonycha affinis Boheman (Coleoptera: Melolonthinae), as soil pests of sugarcane, and a need for their control was established. The development of a mycoinsecticide offers an environmentally friendly alternative to chemical insecticides. The identification of a diversity of white grub species, in two Scarabaeidae subfamilies, representing seven genera were collected in sugarcane as a pest complex. Hypopholis sommeri and S. affinis were the most prevalent species. The increased seasonal abundances, diversity and highly aggregated nature of these scarabaeid species in summer months, suggested that targeting and control strategies for these pests should be considered in this season. Increased rainfall, relative humidity and soil temperatures were linked to the increased occurrence of scarab adults and neonate grubs. Beauveria brongniartii (Saccardo) Petch epizootics were recorded at two sites in the KZN Midlands North on H. sommeri. Seventeen different fluorescently-labelled microsatellite PCR primers were used to target 78 isolates of Beauveria sp. DNA. Microsatellite data resolved two distinct clusters of Beauveria isolates which represented the Beauveria bassiana senso stricto (Balsamo) Vuillemin and B. brongniartii species groups. These groupings were supported by two gene regions, the nuclear ribosomal Internal Transcribed Spacer (ITS) and the nuclear B locus (Bloc) gene of which 23 exemplar Beauveria isolates were represented and sequenced. When microsatellite data were analysed, 26 haplotypes among 58 isolates of B. brongniartii were distinguished. Relatively low levels of genetic diversity were detected in B. brongniartii and isolates were shown to be closely related. There was no genetic differentiation between the two sites, Harden Heights and Canema in the KZN Midlands North. High gene flow from swarming H. sommeri beetles is the proposed mechanism for this lack of genetic differentiation between populations. Microsatellite analyses also showed that B. brongniartii conidia were being cycled from arboreal to subterranean habitats in the environment by H. sommeri beetles. This was the first record of this species of fungus causing epizootics on the larvae and adults of H. sommeri in South Africa. The virulence of 21 isolates of Beauveria brongniartii and two isolates of B. bassiana were evaluated against the adults and larvae of S. affinis and the adults of H. sommeri and Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae). Despite being closely-related, B. brongniartii isolates varied significantly in their virulence towards different hosts and highlighted the host specific nature of B. brongniartii towards S. affinis when compared to B. bassiana. Adults of S. affinis were significantly more susceptible to B. brongniartii isolates than the second (L2) or third instar (L3) grubs. The median lethal time (LT₅₀) of the most virulent B. brongniartii isolate (C13) against S. affinis adults was 7.8 days and probit analysis estimated a median lethal concentration (LC₅₀) of 4.4×10⁷ conidia/ml⁻¹. When L2 grubs were treated with a concentration of 1.0×10⁸ conidia/ml⁻¹, B. brongniartii isolates HHWG1, HHB39A and C17 caused mortality in L2 grubs within 18.4-19.8 days (LT₅₀). Beauveria brongniartii isolate HHWG1 was tested against the L3 grubs of S. affinis at four different concentrations. At the lowest concentration (1×10⁶ conidia/ml⁻¹), the LT₅₀ was 25.8 days, and at the highest concentration (1×10⁹ conidia/ml⁻¹) the LT₅₀ dropped to 15.1 days. The persistence of B. bassiana isolate 4222 formulated on rice and wheat bran and buried at eight field sites in the KZN Midlands North was evaluated by plating out a suspension of treated soil onto a selective medium. All eight field sites showed a significant decline in B. bassiana CFUs per gram of soil over time, with few conidia still present in the samples after a year. Greater declines in CFUs were observed at some sites but there were no significant differences observed in the persistence of conidia formulated on rice or wheat bran as carriers. Overall, poor persistence of B. bassiana isolate 4222 was attributed to suboptimum temperatures, rainfall, which rapidly degraded the nutritive carriers, attenuated fungal genotype and the action of antagonistic soil microbes. Growers’ perceptions of white grubs as pests and the feasibility of a mycoinsecticide market were evaluated by means of a semi-structured questionnaire. The study showed that the reduced feasibility of application, general lack of potential demand for a product, high cost factors and most importantly, the lack of pest perception, were factors which would negatively affect the adoption of a granular mycoinsecticide. Growers however exhibited a positive attitude towards mycoinsecticides, and showed all the relevant attributes for successful technology adoption. It is recommended that because B. brongniartii epizootics were recorded on target pests which indicated good host specificity, dispersal ability and persistence of the fungus in the intended environment of application; that a mycoinsecticide based on this fungal species be developed. What will likely increase adoption and success of a mycoinsecticide is collaboration between various industries partners to increases market potential in other crops such as Acacia mearnsii De Wild (Fabales: Fabaceae).

Genetically modified (GM) white and yellow maize, Zea mays, has been commercially released and cultivated in South Africa since 1997/1998. The traits expressed are insect resistance and herbicide tolerance conferred by the bacteria Bacillus thuringiensis (Bt) Cry genes and Agrobacterium 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase gene, respectively. The Cry genes have been used widely to control lepidopteran insect pests but insect resistance to GM Bt crops has been a concern since the introduction of this technology. A management strategy includes refugia planting of 5% non-Bt plants, with no insecticide application, and 20%, where insecticide application is allowed. These refugia are designed to allow the survival of insect pests within restricted planted zones. However, in South Africa there are reports of Bt-resistant stem borer (Busseola fusca) (Fuller) (Lepidoptera: Noctuidae) and non-compliance with refuge planting. The aims of this study were two-fold: 1. To conduct a survey among KwaZulu-Natal (KZN) GM maize growers to ascertain information such as level of compliance with refuge planting and to determine which refugia were predominantly planted and reasons thereof; 2. To conduct a replicated field trial to determine yield, insect borer damage and economic benefit of the 5% unsprayed and 20% sprayed refuge options (including three configurations namely strip, perimeter and block and a 5 and 20% ‘refuge-in-a-bag’ option). The survey indicated that 28 out of 29 (96.6%) KZN Bt maize growers plant the 5% non-sprayed refuge with 27 (96.4%) of those respondents planting the strip configuration for the purpose of insect management (75%) and ease of planting (32.2%). The survey also showed that 7 (seven) i.e. 21.9% of KZN Bt maize growers observed borer damage and although growers are now fully compliant with refugia planting requirements, initially 7 respondents (24.1%) did not comply with or plant refugia correctly. Furthermore, 7 respondents reported insect borer damage in their maize with 4 of the 7 instances (57.1%) likely stemming from incorrectly planted refugia. vii No significant differences in yield or insect damage were observed between the 5 and 20% refugia for any of the planting configurations in the field trial. However due to costs involved with insecticide application and labour required for the operation in the 20% option, these treatments were less economically advantageous than the non-Bt control. The 20% block and strip configurations had a cost benefit ratio of ZAR 7.21 and ZAR 6.67 respectively, earned per R1 spent by the grower compared with ZAR 7.76 in the sprayed control. The cost-benefit comparison for the 5% block and strip configurations was ZAR 8.48 and ZAR 7.71, respectively compared with ZAR 9.44 in the unsprayed control. In addition, the 20% seed mixture limited borer damage to 4.95% when compared with 15.77% damage in the sprayed control (ANOVA, F pr = 0.124). The seed mixtures are not available commercially and the results from the survey indicated that some education and marketing by the seed companies would be advisable prior to their release to the farming community. In order to determine which of the refuge options between 5 and 20% would be more advantageous for growers overall, regardless of the planting configuration; data were grouped and analysed. There were no significant differences in either the yield or insect damage for the 5 and 20% refugia, but the cost-benefit calculations indicated that the 5% option was more cost effective – for the 5 and 20% refugia, ZAR 7.97 and ZAR 7.15 respectively, earned per ZAR 1 spent by the grower (ANOVA, F pr. = 0.03). This is because no insecticide was used in the 5% treatments. Mean ear damage comparisons between the 5 and 20% refugia showed that the 20% refuge in the perimeter configuration incurred the least damage (2.65% ear damage) compared with 5% perimeter (10.86% ear damage), although the reasons for this are not clear. While the results of the field trials showed no significant differences in insect damage and yield with regard to choice of refuge configuration, monitoring insect resistance management remains an integral part of Bt maize crops in South Africa, in order to delay further resistance development and to prolong the viability of Bt technology. / Agriculture and  Animal Health / M. Sc. (Agriculture)