NEMARIOC-AL AND NEMAFRIC-BL PHYTONEMATICIDES: BIOACTIVITIES IN MELOIDOGYNE INCOGNITA, TOMATO CROP, SOIL TYPE AND ORGANIC MATTER by ZAKHELENI PALANE DUBE THESIS Submitted in fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY in AGRICULTURE (PLANT PRODUCTION) in the FACULTY OF SCIENCE AND AGRICULTURE (School of Agricultural and Environmental Sciences) at the UNIVERSITY OF LIMPOPO, SOUTH AFRICA SUPERVISOR : PROF P.W. MASHELA CO-SUPERVISOR : PROF D. DE WAELE (LEUVEN, BELGIUM) 2016