The problems posed by alien invasive plants to our environment and the need for clearing and control has been highlighted by the Working for Water (WFW) programme. Alien plant control requires careful planning, including budgeting. To date, costing and budgeting in alien plant control has largely been a combination of experience on the part of weed 'experts', coupled with much guess work. Weed controllers have through experience calculated the amount of time (or the work rate), recorded as labour days, required for different control actions of different weed habits. These work rates are for weed clearance under ideal conditions and do not take into account the effect of factors such as gradient, access and distance to the weed infestation. Factors affecting the work rate has been researched and modelled by researchers in both alien plant control and the timber industry. While the existing work rate model is useful in its present theoretical state, the model may be improved upon to make it more practical and applicable to the varying conditions of different areas. This research built on existing theoretical research on alien control work rates, and concentrated on two main areas: the adaption and incorporation of the existing research on work rates into a Geographical Information System (GIS), and the creation and demonstration of a Spatial Decision Support System (SDSS) for the management of alien plant control. The eMpofana river in the KwaZulu-Natal midlands was selected as the study area, as there was an existing alien plant control programme. Initially all factors, such as slope, access to weed infestations, terrain and penetrability of infestations, affecting the work rate in the research area were identified. An existing work rate model was then modified to account for the conditions of the research area. Regression analysis was used to derive the relationship between the various factors affecting work rate, creating a work rate model applicable to the study area. Using the results of the regression analysis together with work rate figures adapted from an existing alien plant control programme, a SDSS for alien plant control along the eMpofana River was created. The use of the work rate model and the SDSS in the development of weed control programmes was demonstrated by examining four different management approaches, each having a different management objective . The SDSS provides a spatial component to weed control planning and costing that has thus far not existed. What this research has achieved is the advancement of an alien control work rate model from a theoretical to a more realistic costing process. While some factors affecting work rate may not have been accounted for, the model does address the present inaccuracies in labour costing, and ultimately alien plant control costing. The research has highlighted the disadvantages of GIS in terms of affordability and expertise. The model has wider uses than the eMpofana River, and is the ground work for the further development of a user friendly model applicable throughout South Africa. More effective project budgeting will decrease the likelihood of project failure and this will directly benefit long-term weed control efforts. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

The dissertation has set the aim to determine the influence of a high-temperature environment on highly resistant to thermal killing. Not all weeds equally respond to the thermal effect when wet water vapour is applied for thermal weed control. After thermal destruction of the above-ground part some varieties of weeds spring up again. Analysis of the morphological structure of weeds and their responsiveness to wet water vapour allows weed classification into three groups: weeds of low resistance to thermal killing, those of high resistance to thermal killing (meadow-grass and rosette weeds) and of very high resistance to thermal killing. If the thermal control of these weeds is carried out too late, weeds overgrow cultivated plants, which results in harvest losses. In order to improve the technology of thermal weed control it was necessary evaluate the parameters of a high-temperature environment, the morphological structure of weeds highly resistant to thermal killing, stages of weed growth and development, the influence of air inter-layers in weed leaves on the spread of a high-temperature field to deeper tissues, and the influence of the angle of tilt of weed leaves on thermal control. This paper analyses the influence of the aforementioned factors on the control of weeds highly resistant to thermal destruction and proposes measures for the formation of a high-temperature environment intended for a more efficient thermal control of weeds using wet water vapour. / Darbo tikslas – nustatyti aukštatemperatūrės aplinkos poveikį sunkiai termiškai sunaikinamoms piktžolėms. Terminei piktžolių kontrolei naudojant drėgną vandens garą, ne visos piktžolės vienodai reaguoja į terminį poveikį. Termiškai sunaikinus antžeminę dalį, atskiros piktžolių rūšys po kurio laiko atželia. Išnagrinėjus piktžolių morfologinę sandarą ir piktžolių jautrumą drėgnam vandens garui, galima piktžoles suskirstyti į tris grupes: lengvai termiškai sunaikinamos, sunkiai termiškai sunaikinamos (miglinės ir skrotelinės piktžolės) ir labai sunkiai termiškai sunaikinamos piktžolės. Terminėje piktžolių kontrolėje didelę problemą kelia sunkiai termiškai sunaikinamos piktžolės. Suvėlinus šių piktžolių terminę kontrolę, piktžolės stelbia žemės ūkio augalus, patiriami derliaus nuostoliai. Norint tobulinti piktžolių terminės kontrolės technologiją teko įvertinti aukštatemperatūrės aplinkos parametrus, sunkiai termiškai sunaikinamų piktžolių morfologinę sandarą, piktžolių augimo ir vystymosi tarpsnius, piktžolių lapų oro tarpsluoksnių įtaką aukštatemperatūrio lauko plitimui į gilesnius audinius, piktžolių lapų posvyrio kampo įtaką terminei kontrolei. Šiame darbe yra nagrinėjama minėtų veiksnių įtaka sunkiai termiškai sunaikinamų piktžolių kontrolei, bei siūlomos sprendimo priemonės formuojant aukštatemperatūrę aplinką efektyvesnei terminei piktžolių kontrolei drėgnuoju vandens garu.

Habitat fragmentation and biological invasions are widely considered to be the most significant threats to global biodiversity, and synergistic interactions between these processes have the potential to cause even greater biodiversity loss than either acting alone. The objective of my study was to investigate the effects of fragmentation on plant communities in native forest fragments, and to examine potential interactions between these effects and invasions by exotic plants at multiple spatial scales. I examined edge, area and landscape effects on plant invasions using empirical data from fragmented landscapes on the West Coast of New Zealand. My research revealed significant interactions between the amount of native forest cover in the landscape and the strength of edge and area effects on plant communities in forest fragments. The dominance of exotic plants in the community was highest at forest edges and decreased towards fragment interiors, however the interiors of very small fragments were relatively more invaded by exotic plants than those in larger fragments, reflecting a significant interaction between edge and area effects. Similarly, exotic dominance increased in more heavily deforested landscapes, but this effect was only apparent in very small fragments (<2 ha). The combined effects of small fragment size and low forest cover in the landscape appear to have promoted invasions of exotic plants in very small remnants. I explored the mechanisms underlying edge-mediated invasions in forest fragments and examined whether propagule availability and/or habitat suitability may be limiting invasions into fragments. Experimental addition of exotic plant propagules revealed that landscape forest cover interacted with edge effects on germination, growth and flowering rates of two short-lived, herbaceous species, and this appeared to be driven by elevated light and soil phosphorus levels at edges in heavily deforested landscapes. I also examined the role of traits in influencing plant responses to forest fragmentation. Different traits were associated with exotic invasiveness in edge and interior habitats of forest fragments, indicating that the traits promoting invasiveness were context dependent. Traits also had a major influence on responses of native plants to forest fragmentation, with generalist species appearing to benefit from fragmentation, as they can utilise both forest and open habitats, whereas native forest specialists have been negatively impacted by fragmentation.

Weed control is a major cost for growers in the sugarcane industry, especially for monocotyledonous species such as Cynodon and Rottboellia spp. The introduction of imazapyr-tolerant sugarcane would be advantageous as this herbicide has shown to be effective against the above-mentioned weeds but it also kills sugarcane. In a previous study in our laboratory, several sugarcane putative-mutant lines of variety N12 were generated by in vitro exposure of embryogenic callus to 16 mM ethyl methanesulfonate (EMS), followed by selection on imazapyr-containing medium. Tolerance to a low dose of imazapyr was confirmed in seven of those lines when the herbicide was applied (182 g a.i. ha-1) to 3 month-old plants in pots. The aim of the present study was to identify which of the seven herbicide mutant lines had agronomic characteristics at least equivalent to un-mutated N12. The objectives were to: 1) confirm tolerance to increased rate (312 and 625 g a.i. ha-1) of imazapyr in field plants; 2) measure the agronomic characteristics of these lines; 3) determine the effect of residual soil herbicide activity on germination of sugarcane setts. The seven mutant lines (Mut1-Mut7) and un-mutated N12 were clonally propagated in vitro by shoot multiplication followed by rooting and planted in three plots (untreated, sprayed with 312 or 625 g a.i. ha-1 imazapyr), in the field, in a randomized complete block design. In the untreated control plot there were no significant differences between the control and the mutant plants for agronomic traits (tiller number/plot, stalk height and stalk diameter) or estimated yield (kg/plot) after 10 months, indicating that the mutation process had no effect on general plant phenotype. In the sprayed (312 and 625 g a.i. ha-1) plots, Mut1, Mut4, Mut5, Mut6 and Mut7 plants showed tolerance to imazapyr as the leaves remained green compared with Mut2, Mut3 and N12 control plants, which displayed chlorotic leaves and eventually died in the plot sprayed with 625 g a.i. ha-1. Post-herbicide application, the yields of Mut5, Mut6 and Mut7 (52.33, 43.43 and 41.43 kg/plot, respectively) from the 312 g a.i. ha-1 plot were not significantly different from that of N12 control (53. 61 kg/plot) in the untreated plot. However, in the 312 g a.i. ha-1 plot, the yield and agronomic trait measurements of the untreated N12 control were significantly higher than those of the herbicide-susceptible plants Mut2 and Mut3. Similarly, in the 625 g a.i. ha-1 plot, the recorded yields for Mut4, Mut6 and Mut7 were 41.60, 43.44 and 36.30 kg/plot, respectively, indicating that their imazapyr tolerance and yield characteristics were comparable to the untreated N12 control. Imazapyr is conventionally applied to a fallow field 3-4 months prior to planting sugarcane as there is residual herbicide activity in the soil that suppresses sugarcane germination and growth. Therefore, in order to establish if the herbicide-tolerant mutants could germinate in iii an imazapyr-treated field, 3-budded setts of the mutant lines (Mut1-Mut7) and N12 control were planted in two plots, one unsprayed and one sprayed with 1254 g a.i. ha-1 imazapyr, 2 weeks previously. Germination was calculated after 3 weeks as the number of germinated setts in each plot/no. germinated setts in unsprayed plot x100. In the sprayed plot, the setts from Mut1, Mut4 and Mut6 displayed the highest germination percentages (60, 71 and 74%, respectively) compared with Mut2 (24%), Mut3 (46%), Mut5 (34%), Mut7 (40%) and the N12 control (12%). The in vitro acetolactate synthase (ALS) enzyme activity of 10 month-old plants from the untreated plot was assessed in the presence of 0-30 μM imazapyr to determine the herbicide concentration that inhibited ALS activity by 50% (IC50). The IC50 values for the mutated lines were between 3 and 30 μM, i.e. 1.5-8.8 times more tolerant to imazapyr than the N12 control plants, with Mut6 displaying the highest IC50 value (30 μM). On the basis of the results, it was concluded that Mut1, Mut6 and Mut7 lines were more tolerant to imazapyr than N12 and the other tested lines. Future work includes phenotypically assessing these lines for traits including sucrose content, fibre content, actual yield (tons cane ha-1) and altered pest and disease resistance. Once isolated and sequenced, the ALS gene conferring imazapyr tolerance can be used in genetic bombardment in the genetic modification approach as the gene of interest or as a selectable marker. In addition, the imazapyr-tolerant line can be used for commercial purposes in the field and as the parent plant in the breeding programme. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Durban, 2013.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 205-240). / Also available by subscription via World Wide Web / xv, 240 leaves ill., maps 29 cm

Tasmanian lacewing, Micromus tasmaniae Walker, is an important predator of a number of economically important pests such as aphids. This study was conducted to investigate some aspects of general biology and factors affecting the reproductive fitness of this species Emergence of M. tasmaniae peaked 3 h before light off and there was no significant difference in emergence patterns between males and females. Males became sexually mature earlier than females. Mating success significantly increased from the first to the eleventh hour after lights on. Predation, development and oviposition of M. tasmaniae were affected when reared under different photoperiods [i.e. 24:0, 16:8, 12:12, 0:24 h (light:dark)]. Results indicate that no individuals entered diapause at either an immature or adult stage. M. tasmaniae larvae could feed in both the photophase and scotophase and late instar larvae consumed significantly more aphids than early instar larvae. M. tasmaniae reared at 16:8 h developed faster and had lower mortality, heavier adult body weight and higher reproductive output in terms of fecundity and fertility rate. Therefore, mass-rearing programmes are recommended to be carried out at 16:8 h to obtain the higher quality of individuals and faster increase of populations. The larger-the better theory predicts that the reproductive fitness is positively linearly associated with body size or weight. However, the body weight of female M. tasmaniae had no effect on the reproductive fitness in terms of fecundity, fertility, fertility rate, oviposition period and longevity. The male body weight may contribute to the population growth of M. tasmaniae as the average females that mated with average or heavy males had significantly higher fecundity, fertility and fertility rate and longer reproductive period. These results suggest that development of any control method that should selectively mass-produce heavy and average individuals in the laboratory would help increasing M. tasmaniae quality and populations. M. tasmaniae is a polygamous species. Results indicate that female remating either with the same or different males was crucial for maximizing their reproductive success. Males could inseminate up to eight females and father about one thousand offspring during their life span.

Tasmanian lacewing, Micromus tasmaniae Walker, is an important predator of a number of economically important pests such as aphids. This study was conducted to investigate some aspects of general biology and factors affecting the reproductive fitness of this species Emergence of M. tasmaniae peaked 3 h before light off and there was no significant difference in emergence patterns between males and females. Males became sexually mature earlier than females. Mating success significantly increased from the first to the eleventh hour after lights on. Predation, development and oviposition of M. tasmaniae were affected when reared under different photoperiods [i.e. 24:0, 16:8, 12:12, 0:24 h (light:dark)]. Results indicate that no individuals entered diapause at either an immature or adult stage. M. tasmaniae larvae could feed in both the photophase and scotophase and late instar larvae consumed significantly more aphids than early instar larvae. M. tasmaniae reared at 16:8 h developed faster and had lower mortality, heavier adult body weight and higher reproductive output in terms of fecundity and fertility rate. Therefore, mass-rearing programmes are recommended to be carried out at 16:8 h to obtain the higher quality of individuals and faster increase of populations. The larger-the better theory predicts that the reproductive fitness is positively linearly associated with body size or weight. However, the body weight of female M. tasmaniae had no effect on the reproductive fitness in terms of fecundity, fertility, fertility rate, oviposition period and longevity. The male body weight may contribute to the population growth of M. tasmaniae as the average females that mated with average or heavy males had significantly higher fecundity, fertility and fertility rate and longer reproductive period. These results suggest that development of any control method that should selectively mass-produce heavy and average individuals in the laboratory would help increasing M. tasmaniae quality and populations. M. tasmaniae is a polygamous species. Results indicate that female remating either with the same or different males was crucial for maximizing their reproductive success. Males could inseminate up to eight females and father about one thousand offspring during their life span.

Tasmanian lacewing, Micromus tasmaniae Walker, is an important predator of a number of economically important pests such as aphids. This study was conducted to investigate some aspects of general biology and factors affecting the reproductive fitness of this species Emergence of M. tasmaniae peaked 3 h before light off and there was no significant difference in emergence patterns between males and females. Males became sexually mature earlier than females. Mating success significantly increased from the first to the eleventh hour after lights on. Predation, development and oviposition of M. tasmaniae were affected when reared under different photoperiods [i.e. 24:0, 16:8, 12:12, 0:24 h (light:dark)]. Results indicate that no individuals entered diapause at either an immature or adult stage. M. tasmaniae larvae could feed in both the photophase and scotophase and late instar larvae consumed significantly more aphids than early instar larvae. M. tasmaniae reared at 16:8 h developed faster and had lower mortality, heavier adult body weight and higher reproductive output in terms of fecundity and fertility rate. Therefore, mass-rearing programmes are recommended to be carried out at 16:8 h to obtain the higher quality of individuals and faster increase of populations. The larger-the better theory predicts that the reproductive fitness is positively linearly associated with body size or weight. However, the body weight of female M. tasmaniae had no effect on the reproductive fitness in terms of fecundity, fertility, fertility rate, oviposition period and longevity. The male body weight may contribute to the population growth of M. tasmaniae as the average females that mated with average or heavy males had significantly higher fecundity, fertility and fertility rate and longer reproductive period. These results suggest that development of any control method that should selectively mass-produce heavy and average individuals in the laboratory would help increasing M. tasmaniae quality and populations. M. tasmaniae is a polygamous species. Results indicate that female remating either with the same or different males was crucial for maximizing their reproductive success. Males could inseminate up to eight females and father about one thousand offspring during their life span.

Tasmanian lacewing, Micromus tasmaniae Walker, is an important predator of a number of economically important pests such as aphids. This study was conducted to investigate some aspects of general biology and factors affecting the reproductive fitness of this species Emergence of M. tasmaniae peaked 3 h before light off and there was no significant difference in emergence patterns between males and females. Males became sexually mature earlier than females. Mating success significantly increased from the first to the eleventh hour after lights on. Predation, development and oviposition of M. tasmaniae were affected when reared under different photoperiods [i.e. 24:0, 16:8, 12:12, 0:24 h (light:dark)]. Results indicate that no individuals entered diapause at either an immature or adult stage. M. tasmaniae larvae could feed in both the photophase and scotophase and late instar larvae consumed significantly more aphids than early instar larvae. M. tasmaniae reared at 16:8 h developed faster and had lower mortality, heavier adult body weight and higher reproductive output in terms of fecundity and fertility rate. Therefore, mass-rearing programmes are recommended to be carried out at 16:8 h to obtain the higher quality of individuals and faster increase of populations. The larger-the better theory predicts that the reproductive fitness is positively linearly associated with body size or weight. However, the body weight of female M. tasmaniae had no effect on the reproductive fitness in terms of fecundity, fertility, fertility rate, oviposition period and longevity. The male body weight may contribute to the population growth of M. tasmaniae as the average females that mated with average or heavy males had significantly higher fecundity, fertility and fertility rate and longer reproductive period. These results suggest that development of any control method that should selectively mass-produce heavy and average individuals in the laboratory would help increasing M. tasmaniae quality and populations. M. tasmaniae is a polygamous species. Results indicate that female remating either with the same or different males was crucial for maximizing their reproductive success. Males could inseminate up to eight females and father about one thousand offspring during their life span.

Tasmanian lacewing, Micromus tasmaniae Walker, is an important predator of a number of economically important pests such as aphids. This study was conducted to investigate some aspects of general biology and factors affecting the reproductive fitness of this species Emergence of M. tasmaniae peaked 3 h before light off and there was no significant difference in emergence patterns between males and females. Males became sexually mature earlier than females. Mating success significantly increased from the first to the eleventh hour after lights on. Predation, development and oviposition of M. tasmaniae were affected when reared under different photoperiods [i.e. 24:0, 16:8, 12:12, 0:24 h (light:dark)]. Results indicate that no individuals entered diapause at either an immature or adult stage. M. tasmaniae larvae could feed in both the photophase and scotophase and late instar larvae consumed significantly more aphids than early instar larvae. M. tasmaniae reared at 16:8 h developed faster and had lower mortality, heavier adult body weight and higher reproductive output in terms of fecundity and fertility rate. Therefore, mass-rearing programmes are recommended to be carried out at 16:8 h to obtain the higher quality of individuals and faster increase of populations. The larger-the better theory predicts that the reproductive fitness is positively linearly associated with body size or weight. However, the body weight of female M. tasmaniae had no effect on the reproductive fitness in terms of fecundity, fertility, fertility rate, oviposition period and longevity. The male body weight may contribute to the population growth of M. tasmaniae as the average females that mated with average or heavy males had significantly higher fecundity, fertility and fertility rate and longer reproductive period. These results suggest that development of any control method that should selectively mass-produce heavy and average individuals in the laboratory would help increasing M. tasmaniae quality and populations. M. tasmaniae is a polygamous species. Results indicate that female remating either with the same or different males was crucial for maximizing their reproductive success. Males could inseminate up to eight females and father about one thousand offspring during their life span.