i PREVALENCE, DETECTION AND CHARACTERIZATION OF TOMATO SPOTTED WILT AND IRIS YELLOW SPOT TOSPOVIRUSES OCCURING IN ZIMBABWE By Charles Karavina (213573967) MSc Crop Protection; BSc Agriculture Hons (Crop Science) Submitted in partial fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Discipline of Plant Pathology School of Agricultural, Earth and Environmental Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal Pietermaritzburg, South Africa June 2017