Tritrophic interaction between whiteflies, insect pathogenic fungi and host plant : biology of whitefly, Bemisia afer

Abstract: The study was preformed at the International Potato Centre, CIP, in the capital of Peru, Lima on the west coast of South America and the Ecology Department, SLU, Uppsala, Sweden. The main purpose of this thesis was to evaluate the tritrophic interaction and efficacy of entomopathogens on the whitefly on different host plants and different species of fungus. Included was a study on the life cycle of the whitefly specie Bemisia afer on four host plants. Greenhouse trials were carried out at CIP and all conditions like temperature, as well as daylight and night were controlled and held at the same level throughout the whole study to obtain as similar a comparison as possible in between the trials. Each trial was repeated three times and evaluated all together in the end. The leaves from the four host plants, which were used, were always the youngest but fully developed ones. To keep the whiteflies in good condition, they were held on sweetpotato plants and strictly kept under control from predators and other insects. The fungus was cultured during the trial to keep them young and healthy and free from other agents. The results of the tritrophic interaction study showed no significant differences between different host plants neither between the different fungi nor strain of fungi and their effect when combating the whiteflies. The life cycle showed some differential behaviour between the host plants and results may show certain behaviour of the whitefly in the field. For example, there were differences in development time of B. afer on different host plants. Different characters of host plant causing a special microclimate on leaves might have had an influence on the development time and problems during the growth of the nymphs.