Cases of atrazine damage to maize, and occasional reports of excessive residue persistence that caused injury to susceptible following crops, prompted research on factors which influence the bioactivity and persistence of the herbicide. Bioassays with several indicator species were conducted in the field and in glasshouses. Measurement of atrazine by chemical means was done in only three of the experiments. Maize seedlings were not more sensitive to atrazine when stressed by insufficient supplies of N, P , K, Ca or Mg. Neither high P supply nor phytotoxic P concentrations in maize seedlings lowered their tolerance to atrazine. These findings on the roles of certain nutrients in the tolerance of maize to atrazine concluded a series of investigations into damage reported in the field. No satisfactory evidence for the factors which rendered maize susceptible to atrazine in the field was ever found. Another investigation showed that atrazine threshold concentrations for certain susceptible species varied from soil to soil , indicating that differential availability of the herbicide for uptake by plants in different soils precludes the allocation of fixed atrazine threshold values to different crop species. Atrazine bioactivity and persistence varied considerably in a series of field experiments which were conducted to determine the order of importance of certain soil properties in the prediction of short- and long-term bioactivity. Soil organic matter content (% C) was the best predictor in both instances. Soil pH was a poor predictor of short-term bioactivity, but became more prominent with time. Organic matter, pH and P-reversion accounted for 35%, 19% and 14% of the variation in bioactivity measured six months after atrazine application in the field. In view of the variation in atrazine persistence, and therefore, the potential for variable carry-over from soil to soil, the applicability of the recropping interval recommended for dry beans and sunflower were investigated. It was concluded that the specification could be justified for sunflower only, but then only on certain soils. It is suggested that recropping intervals , which are recommended for certain crops after atrazine use in maize, be refined on the basis of differences in follow-up crop sensitivity to atrazine, and relationships between atrazine persistence and certain soil properties. Chemical analysis showed that soil type and soil water content had greater influences on atrazine persistence than temperature. Irrespective of soil type, the rate of atrazine breakdown was faster in soil at a water content of field capacity, and in water-logged soil (2x FC), than in air-dry soil. A bioassay technique was used to estimate the concentration of atrazine and/or its phytotoxic residues in a soil profile. Basically the same procedure was followed in an incubation study with 25 soils to develop the following regression model for prediction of atrazine half-life in soil: γ = -2.29 + I.77xl + 20.8Ix2, where γ is half-life in days; Xl = [soil pH(H2O)2<f and X2 = % C. The bioassay technique proved useful for estimating total amounts of atrazine and its phytotoxic residues in various soil type AFRIKAANS : Beskadiging van mielies deur atrasien, en sporadiese berigte van oormatige nawerking met gepaardgaande beskadiging van gevoelige opvolggewasse, het aanleiding gegee tot navorsing oor faktore wat die bio-aktiwiteit en nawerking van die onkruiddoder be'invloed, Biotoetse is met verskillende toetsplante in glashuis- en veldproewe uitgevoer. Bepaling van atrasien deur chemiese analise is in slegs drie proewe gedoen , Mieliesaailinge se verdraagsaamheid teenoor atrasien is nie deur tekorte aan N , P, K, Ca en Mg in die plante be'invloed nie, Nog hoe P-voorsiening, nog fitotoksiese Pkonsentrasies in saailinge, het hul weerstand teen atrasien verlaag, Hierdie bevindings oor die rol van sekere voedingselemente by die verdraagsaamheid van mielies teenoOT atrasien het 'n reeks ondersoeke na destydse skade in die veld afgesluit, sonder bevredigende verklarings vir die probleem, In'n ander ondersoek is gevind dat drumpelwaarde-konsentrasies van atrasien vir bepaalde gevoelige gewasplante van grond tot grond varieer. Differensiele beskikbaarheid van atrasien in grond sal dus die toekenning van 'n vaste drumpelwaarde aan 'n bepaalde gewasplant verhoed , Dieorganiese koolstofinhoud van grond was die belangrikste voorspeller van die kort- en langtermyn bio-aktiwiteit van atrasien in 'n reeks veldproewe. Die variasie in bioaktiwiteit wat ses maande na toediening van die doder deur organiese materiaalinhoud, pH en P-reversie verklaar is, was onderskeidelik 35% , 19% en 14%. Derhalwe het grond-pH , wat 'n swak voorspeller (l % van variasie) van die korttermyn-aktiwiteit van atrasien was, belangriker geraak met tyd. Die bio-aktiwiteit en nawerking van atrasien het aansienlik tussen lokaliteite verskil. Weens die varierende nawerking van atrasien in grond , en gevolglike verskille in die potensiele oordraging van atrasien na 'n volgende seisoen , is die toepasLikheid van die wagperiode wat vir droebone en sonneblom gestel word vervolgens ondersoek. Die voorgeskrewe wagperiode kon slegs vir sonneblom as toepaslik bevestig word , en dan slegs op sekere grondsoorte. Dit word voorgestel dat wagperiodes verfyn behoort te word op basis van verski lle tussen grondsoorte en die verdraagsaamheid van gewasplante teenoor atrasien. Met chemiese analise is bepaal dat grondsoort en -waterinhoud 'n belangriker effek op nawerking van atrasien as temperatuur gehad het. Vergeleke met die afbraaktempo in 11Igdroe grond het atrasien vinniger afgebreek in grond waar die waterinholld by veldkapasiteit was, asook wanneer dit twee keer hierdie hoeveelheid water bevat het. 'n Biotoetstegniek is gebruik vir skatting van atrasien- en/of fitotoksiese residu-konsentrasies in 'n grondprofiel. Basies dieselfde prosed lire is in 'n inkubasieproef met 25 gronde toegepas vir ontwikkeling van die volgende model vir voorspelling van die halfleeftyd van atrasien in grond: γ = -2.29 + l.77x1 + 20.8Ix2, waar γ halfleeftyd in dae is; x1 = [grond-pH(H20)]2 en x2 = % C. Die biotoetstegniek was effektief vir skattings van die totale hoeveelheid atrasien en fitotoksiese atrasienresidue in grond. / Thesis (PhD)--University of Pretoria, 2011. / Plant Production and Soil Science / unrestricted

Based on surface area, South Africa is currently ranked 8th in planting genetically modified (GM) crops in the world. The stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is of economic importance throughout sub–Saharan Africa. Bt maize (MON810) has been grown to control lepidopterous stem borers in South Africa since its first release in 1998. The first report of resistance to Bt maize was made in the Christiana area of South Africa in 2007. The objectives of this study were to evaluate the status of resistance of populations of B. fusca to Bt maize; to evaluate farmers' perceptions of the regulatory aspects guiding the planting of Bt maize and refugia and how the field situation developed between 1998 and 2010; to compare the fitness of the fertility, fecundity and longevity of Bt–resistant and susceptible B. fusca populations and to determine if there are fitness costs associated with resistance of B. fusca to Bt maize. Questionnaire surveys were conducted amongst 185 farmers in seven districts throughout the maize production region. The questionnaire addressed signing of contracts upon purchasing GM seed, refuge compliance, pest management practices, perceived benefits and risks relating to Bt maize. In order to study fitness and fitness costs that may be associated with resistance development, the life history parameters of known Bt–resistant and susceptible populations were compared in the laboratory using a diapauses–as well as second–generation populations collected in maize fields. The following parameters were compared between different stem borers populations and treatments: pupal mass, moth longevity, fecundity, fertility, larval mass and survival, and sex ratio. This study confirmed resistance of B. fusca to the Cry1Ab toxin (MON810) and that larvae collected from refugia at Vaalharts were resistant and survived on Bt maize. Compliance to refugia requirements was low especially during the initial 5 – 7 years after release. An alarmingly high number of farmers applied insecticides as preventative sprays on Bt maize and refugia. Except for moth longevity and LT50– values, no other fitness costs were observed to be associated with the resistance trait in the highly resistant B. fusca population used in this study. The LT50 may indicate some degree of fitness cost but does not translate into observable costs in terms of fecundity, larval mass and survival. The absence of fitness costs may promote the use of alternative Bt–resistance management strategies, such as the introduction of a multigene strategy. The introduction of a stacked event such as MON89034 which produces more than one protein with activity active against the resistant target pest, together with compliance to the refuge strategy, is most likely the only solution to managing Btresistant stem borer populations in South Africa. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

The purpose of the research was to explore the experiences of educators regarding the training for the implementation of inclusive education in a Full Service school. A qualitative research design was chosen, using a case study. Three methods of gathering data were used, namely individual interviews, focus group interviews and observations. The study was conducted in a primary schools in the North West province that was converted into a fullservice school in 2008. The findings indicated that educators demonstrated misunderstanding of the Screening, Identification, Assessment and Support strategy. The misunderstanding can be ascribed to the kind of training educators received. The training lacked in–depth content and practical demonstration. Recommendations on the content and the dynamics of the training process are made. The overarching recommendation on the dynamics of the training indicated that the training should be revisited for improved methods of training. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

Based on surface area, South Africa is currently ranked 8th in planting genetically modified (GM) crops in the world. The stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is of economic importance throughout sub–Saharan Africa. Bt maize (MON810) has been grown to control lepidopterous stem borers in South Africa since its first release in 1998. The first report of resistance to Bt maize was made in the Christiana area of South Africa in 2007. The objectives of this study were to evaluate the status of resistance of populations of B. fusca to Bt maize; to evaluate farmers' perceptions of the regulatory aspects guiding the planting of Bt maize and refugia and how the field situation developed between 1998 and 2010; to compare the fitness of the fertility, fecundity and longevity of Bt–resistant and susceptible B. fusca populations and to determine if there are fitness costs associated with resistance of B. fusca to Bt maize. Questionnaire surveys were conducted amongst 185 farmers in seven districts throughout the maize production region. The questionnaire addressed signing of contracts upon purchasing GM seed, refuge compliance, pest management practices, perceived benefits and risks relating to Bt maize. In order to study fitness and fitness costs that may be associated with resistance development, the life history parameters of known Bt–resistant and susceptible populations were compared in the laboratory using a diapauses–as well as second–generation populations collected in maize fields. The following parameters were compared between different stem borers populations and treatments: pupal mass, moth longevity, fecundity, fertility, larval mass and survival, and sex ratio. This study confirmed resistance of B. fusca to the Cry1Ab toxin (MON810) and that larvae collected from refugia at Vaalharts were resistant and survived on Bt maize. Compliance to refugia requirements was low especially during the initial 5 – 7 years after release. An alarmingly high number of farmers applied insecticides as preventative sprays on Bt maize and refugia. Except for moth longevity and LT50– values, no other fitness costs were observed to be associated with the resistance trait in the highly resistant B. fusca population used in this study. The LT50 may indicate some degree of fitness cost but does not translate into observable costs in terms of fecundity, larval mass and survival. The absence of fitness costs may promote the use of alternative Bt–resistance management strategies, such as the introduction of a multigene strategy. The introduction of a stacked event such as MON89034 which produces more than one protein with activity active against the resistant target pest, together with compliance to the refuge strategy, is most likely the only solution to managing Btresistant stem borer populations in South Africa. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

The purpose of the research was to explore the experiences of educators regarding the training for the implementation of inclusive education in a Full Service school. A qualitative research design was chosen, using a case study. Three methods of gathering data were used, namely individual interviews, focus group interviews and observations. The study was conducted in a primary schools in the North West province that was converted into a fullservice school in 2008. The findings indicated that educators demonstrated misunderstanding of the Screening, Identification, Assessment and Support strategy. The misunderstanding can be ascribed to the kind of training educators received. The training lacked in–depth content and practical demonstration. Recommendations on the content and the dynamics of the training process are made. The overarching recommendation on the dynamics of the training indicated that the training should be revisited for improved methods of training. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

The high-dose/refuge strategy is used globally to manage insect resistance development in genetically modified crops with insecticidal properties (Bt crops). The “refuge in a bag” (RIB) strategy is also being considered for deployment against several pest species. Busseola fusca, the target pest of Bt maize in South Africa, evolved resistance to Cry1Ab proteins. The objective of this study was to determine whether migrating B. fusca larvae are effectively controlled using the RIB strategy. A field study with a single-gene event (Cry1Ab) and a “pyramid” event (Cry1A.105 + Cry2Ab2) was conducted in which the migration patterns of B. fusca larvae in plots with different seed mixture treatments were studied. The experiment consisted of five seed mixture ratios (5%, 10%, 15%, 20% non-Bt seed and 100 % non-Bt seed as control). Natural infestation was augmented by artificial inoculation with neonate larvae into the central non-Bt maize plant of each plot. Rate of larval survival and migration, measured in terms of increase in number of plants per plot that exhibited borer damage was recorded at weekly intervals until flowering. A laboratory study was conducted to determine larval growth and survival when simulating migration between Bt and non-Bt maize plants. A feeding experiment in which larvae were reared on different types of maize (Bt and non-Bt) was conducted and larval survival and mass recorded after a 7-day feeding period. The incidence of damaged ears, stem damage and damaged internodes per stem were recorded and relationships between these variables determined by means of correlation analyses. A review was conducted in order to identify and discuss similarities and differences between the high-dose/refuge and seed mixture strategies. This was done to determine which strategy would be the most appropriate insect resistance management (IRM) strategy against B. fusca. The rate of survival and migration of B. fusca larvae was significantly higher in the plots with maize expressing Cry1Ab and control plots, than in plots with the pyramid Bt event. Older larvae exhibited improved growth and survival in the laboratory experiment when they were transferred from non-Bt to Bt plants. Positive correlations were found between early and late season damage, although some weaker than others. Plants of the “pyramid event” suffered less late-season damage than those of the single-gene event. Since the increase in number of damaged maize plants over time is associated with migration of older and larger larvae, the observed tendencies may indicate that the assumed high-dose does not kill larvae above a certain developmental stage. The high-dose refuge strategy seems to be the better option for delaying resistance development. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Genetically modified (GM) maize was developed mainly to control lepidopteran pests such as the maize stem borer (Busseola fusca) (Lepidoptera: Noctuidae). Since the first commercialization of GM crops with insecticidal properties, possible non-target effects such as the effect at the third trophic level on important predators for example lacewing species (Chrysoperla spp.) have been of concern. Contradicting results were reported in previous studies with regard to the effect of Cry 1Ab protein produced by Bt maize on the performance of lacewings. Some studies found that Bt proteins had no effect while others reported that C. carnea performed poorly if they consumed prey that consumed Cry 1Ab protein. In South Africa one of the most common chrysopid species in maize ecosystems is Chrysoperla pudica (Navás) (Neuroptera: Chrysopidae). Evolution of Bt resistant pests, such as B. fusca in South Africa facilitates a new pathway for exposure of predators to healthy prey that consumes Cry 1Ab proteins. The aims of this study was to determine the effect of the Cry 1Ab protein expressed in Bt maize on a non-target organism‟s (C. pudica) biology via indirect exposure, and to determine the concentration of Cry 1Ab protein in the plant, prey and predator. Chrysoperla pudica larvae were indirectly exposed to the Bt-toxin through healthy Bt-maize feeding prey (B. fusca larvae) in two feeding experiments and lacewing survival and life history parameters recorded. Bt had a limited effect on some parameters that were evaluated. The larval and pupal periods of C. pudica larvae that were exposed to the Bt-toxin had a significant difference from that of the control treatment. The Bt-toxin had a significant effect on fecundity, fertility and malformation after emergence of C. pudica adults of which larvae fed only on Bt resistant B. fusca larvae, but not on the mortality rate. Cry 1Ab concentration was the highest in the plant, followed by the prey and lacewing larvae. This study showed that the Cry 1Ab protein had a slight adverse effect only on certain life parameters of C. pudica, and that Cry 1Ab protein was hardly detectable in C. pudica larvae. However, since this study represented a worst-case scenario where diverse prey was not available, insignificant effects is expected under field conditions where prey is diverse. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

It is widely believed among South African agricultural market participants that the United States' corn price, as represented by the Chicago Board of Trade-listed corn contract, is causal to the price of white and yellow maize traded on the South African Futures Exchange. Although a strong correlation exists between these markets, the corn contract is far from causal to the South African maize price, as indicated by Auret and Schmitt (2008). Similarly, South African market participants believe that volatility generated in the United States corn market spills over to the South African market. Given the perceived volatility spill-over from the corn market to the maize market, market participants might inadvertently include a higher volatility component in an option price in the South African maize market than is necessary. This study sought to quantify the amount of volatility spill-over to the South African white and yellow maize market from the United States corn contract. This task was accomplished by applying an Exponential Generalised Auto Regressive Conditional Heteroscedasticity model, within an aggregate shock framework, to the data. The findings indicated that the volatility spill-over from the United States corn market to the South African maize market is not statistically significant. This result suggests that volatility in the South African market is locally driven; hence, it should not be necessary for a South African listed option contract to carry an international volatility component in its price. It was also found that the returns data of the South African maize market is asymmetrically skewed, indicating that bad news will have a greater effect on the price of maize compared with good news. / Thesis (MCom (Risk Management))--North-West University, Potchefstroom Campus, 2013.

Genetically modified maize expressing the Bt-protein Cry1Ab (Bt maize) is planted widely in South Africa. Crop residues of Bt maize often end up in aquatic ecosystems where aquatic organisms are exposed to Cry1Ab protein. The effect of this protein on non-target aquatic organisms has not yet been studied in South Africa. The aim of this study was to evaluate the possible effect of exposure to Bt maize on morphological development of Xenopus laevis and Amietophrynus gutturalis tadpoles. Three experiments were conducted with each of X. laevis and A. gutturalis. Five of these were conducted in the bio-secure Amphibian Biology laboratory and one with A. gutturalis in a shade-house facility where microcosms were exposed to natural conditions. In the first experiment of X. laevis and A. gutturalis, which was replicated three times, large portions of maize leaves were placed in the bottoms of microcosms. X. laevis received supplementary pulverised leaves in suspension while A. gutturalis tadpoles fed on provided leaves. For both control and experimental groups microcosms were divided in three groups receiving respectively 15, 30 and 45 g of maize leaves. In the second and third experiment tadpoles only received pulverised Bt maize leaves in suspension. Each replicate (microcosm) contained 50 one-day old tadpoles. Experiment two was conducted to determine whether the Bt-protein has adverse effects on A. gutturalis tadpoles when tadpoles are exposed to the protein in the water but not feeding on the plant material. A total of 100 tadpoles were used during the experiment and tadpoles were placed individually in 250 ml plastic cups that were filled with 100 ml water witch contained an extract of either Bt and non-Bt maize leaves. Tadpoles were fed twice a week with TetraTabimin bottom-feeding fish pellets in suspension. Experiment three was conducted to determine whether the Bt-protein will have adverse effects on A. gutturalis tadpoles when tadpoles feed on Bt maize leaves. Tadpoles were divided into a treatment in which 50 tadpoles were fed Bt maize leaves and a control treatment in which 50 tadpoles were fed non-Bt maize leaves. Tadpoles were placed individually in 250 ml plastic cups that were each filled with 100 ml borehole water. On a weekly basis 10 randomly selected tadpoles were collected, measured and staged for morphological development, using the Nieuwkoop and Faber Normal Table for X. laevis and Gosner stages for A. gutturalis tadpoles. The significant effects observed in some life history parameters of tadpoles exposed to Cry1Ab protein cannot be ascribed to the effect of the protein. Poor husbandry turned out to be the single most important confounding factor. Before follow-up studies are conducted husbandry practices should be optimized. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013.

The high-dose/refuge strategy is used globally to manage insect resistance development in genetically modified crops with insecticidal properties (Bt crops). The “refuge in a bag” (RIB) strategy is also being considered for deployment against several pest species. Busseola fusca, the target pest of Bt maize in South Africa, evolved resistance to Cry1Ab proteins. The objective of this study was to determine whether migrating B. fusca larvae are effectively controlled using the RIB strategy. A field study with a single-gene event (Cry1Ab) and a “pyramid” event (Cry1A.105 + Cry2Ab2) was conducted in which the migration patterns of B. fusca larvae in plots with different seed mixture treatments were studied. The experiment consisted of five seed mixture ratios (5%, 10%, 15%, 20% non-Bt seed and 100 % non-Bt seed as control). Natural infestation was augmented by artificial inoculation with neonate larvae into the central non-Bt maize plant of each plot. Rate of larval survival and migration, measured in terms of increase in number of plants per plot that exhibited borer damage was recorded at weekly intervals until flowering. A laboratory study was conducted to determine larval growth and survival when simulating migration between Bt and non-Bt maize plants. A feeding experiment in which larvae were reared on different types of maize (Bt and non-Bt) was conducted and larval survival and mass recorded after a 7-day feeding period. The incidence of damaged ears, stem damage and damaged internodes per stem were recorded and relationships between these variables determined by means of correlation analyses. A review was conducted in order to identify and discuss similarities and differences between the high-dose/refuge and seed mixture strategies. This was done to determine which strategy would be the most appropriate insect resistance management (IRM) strategy against B. fusca. The rate of survival and migration of B. fusca larvae was significantly higher in the plots with maize expressing Cry1Ab and control plots, than in plots with the pyramid Bt event. Older larvae exhibited improved growth and survival in the laboratory experiment when they were transferred from non-Bt to Bt plants. Positive correlations were found between early and late season damage, although some weaker than others. Plants of the “pyramid event” suffered less late-season damage than those of the single-gene event. Since the increase in number of damaged maize plants over time is associated with migration of older and larger larvae, the observed tendencies may indicate that the assumed high-dose does not kill larvae above a certain developmental stage. The high-dose refuge strategy seems to be the better option for delaying resistance development. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014