Potentials and prospects of strip cropping in the management of cassava whitefly (Bemisia tabaci) in peri - urban agroecosystems

Cassava (Manihot esculenta Crantz, Euphorbiaceae) is one of the main tuber crops that occupy an exceptionally important position as a food security commodity for smallholder farmers in sub-Saharan Africa. However, cassava mosaic virus disease (CMD) caused by cassava mosaic geminiviruses (CMGs) (Geminiviridae: Begomovirus) and transmitted by whitefly (Bemisia tabaci) threatens the production of this crop in Africa, causing an estimated annual yield loss of over 1.5 billion US dollars. Control measure to date has been the use of virus-resistant varieties, but low cost cultural control measures such as intercrops or manipulation of the cropping system have been relegated to the background. Most African farmers are unable to afford insecticides for the control of this insect while the insect has developed resistance against most classes of insecticides. This thesis examines the possibility of manipulating the cropping system using strip crops, a low cost and low input cultural control method, in managing Bemisia tabaci populations in cassava. A significantly lower number (P < 0.05) of immature (egg and nymph) and adult Bemisia tabaci were found in cassava plots surrounded on all sides by five rows of both cotton and Jatropha curcas. Additionally, J. curcas strips appeared to repel Bemisia tabaci and lower its populations in cassava. Planting of J. curcas around cassava plots also lowered CMD severity in cassava significantly. Future studies including investigations into the insecticidal and ovicidal properties of J. curcas will elucidate the behavioral and physiological mechanism for whitefly suppression in cassava.