The neotropical semi-woody perennial shrub Chromolaena odorata (L.) King and Robinson (Asteraceae: Eupatorieae) has become a serious invasive weed in the sub-tropical regions of southern Africa, resulting in the initiation of an insect biocontrol research programme at Cedara in the KwaZulu-Natal province. The programme has experienced difficulties in growing and maintaining healthy potted C. odorata plants for research, for almost ten years. In an attempt to identify possible causes of mortality, plants were grown on elevated grids in two trials; (winter-spring 2003) and (autumn-winter 2004) in Durban (subtropical region, within the natural range of C. odorata) and Cedara (temperate region, outside its natural range). Plants that established at all sites, in Trials 1 and 2, did not display any visual symptoms associated with mortality; however, results from Trial 1 indicated that plants grown in a tunnel at Cedara were physiologically stressed evidenced by lower transpiration rates despite higher vapour pressure deficits, compared with plants grown in a tunnel in Durban. Environmental stress was further indicated by the chlorophyll fluorescence ratio and a change in allocation of total non-structural carbohydrate (TNC) within Cedara-grown plants compared with Durbangrown plants. An attempt to relate mortality symptoms of unhealthy C. odorata plants with TNC content of the roots was unsuccessful but unhealthy plants had lower levels of N, P and K than healthy plants. Although mortality seem to be exacerbated by pathogenic fungi in saturated soil, infection was reduced by treating the soil with Previcur N and Benlate drench. Morphological adaptations of plants exposed to waterlogged soils include hypertrophied lenticels and new lateral roots; these were observed on the stem base of unhealthy C. odorata plants placed on the ground, that had reached a critical stage of die-back or had died back and re-sprouted. Examination of the root anatomy of C. odorata plants indicated an absence of cortical aerenchyma (interconnected system of air spaces), which may explain plant mortality in waterlogged pots wherein levels of oxygen in the soil may be reduced. C. odorata stock plants at Cedara have been placed on elevated grids since August 2004 and two years later plant mortality has been significantly reduced. Presently, the only feasible option is to grow potted C. odorata plants on elevated grids at Cedara because this allows for adequate drainage, aeration of soil and air-nipping of roots, and spacing plants on the grids also improves penetration of light. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2007.

Common teasel (Dipsacus fullonum L.) has become an aggressive invasive species throughout most of North America, invading roadsides, ditches, rights of way, pastures, and natural areas. This study examined three herbicides used to control common teasel: 1) BK 800, a 2,4-D based broad-leaf herbicide mixed in diesel fuel; 2) Glyphomax® a non-selective glyphosate-based product mixed in water with 5 mL/L of a non-ionic surfactant (Nu-Film®-IR) added; and 3) Transline®, a clopyralid based broad-leaf herbicide used for non-crop areas with 5 mL/L of the Nu-Film®-IR. The herbicides were applied in three concentrations taken directly from the label specifications: the low end, the high end, and the midpoint between the low and high ends. Plant rosette counts taken two weeks after application were compared to counts taken earlier to create a "survival ratio." The majority of the applications resulted in total kill of all common teasel rosettes. Ratios were compared among all treatment groups and the control. All herbicide treatments resulted in significantly (p<0.001) more kills than the control. The different concentrations of each treatment were compared against each other to determine the optimum concentration for common teasel control. The 2 mL/L concentration of Transline®, the 13 mL/L concentration of Glyphomax® and the 55 mL/L of BK 800 were the most effective treatments. There was no significant difference among the efficacies of the three above herbicides. This study provides the first known quantitative study of herbicidal control of common teasel, and it should serve as a starting point for future studies on controlling this invasive plant. / Department of Natural Resources and Environmental Management

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Thesis (M.S.)--Ohio University, June, 2007. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.S.)--Georgia Southern University, 2007. / "A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." Under the direction of Lissa M. Leege. ETD. Electronic version approved: May 2007. Includes bibliographical references (p. 92-101)

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: p. 169-180.

Thesis (M.Sc.). / Written for the Dept. of Biology. Title from title page of PDF (viewed 2008/07/24). Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains vi, 98 p. : ill., map. Vita. Includes abstract. Includes bibliographical references.

Thesis (M.S.)--Missouri State University, 2008. / "May 2008." Includes bibliographical references (leaves 28-31). Also available online.