EFFECT OF CASTOR BEAN (Ricinus communis L.) AQUEOUS EXTRACTS ON THE PERFORMANCE OF ROOT-KNOT NEMATODES (Meloidogyne spp.) ON TOMATO (Solanum lycopersicum L.)

The increased concern for environmental and health hazards have called for a reduction in the use of synthetic nematicides for nematode control. Experiments were, therefore, conducted to ascertain the nematicidal potential of castor bean’s crude extract and its five lower concentrations with water as control. In the in vitro studies, crude castor bean aqueous extract and 10, 20, 30 and 40% different concentrations with 100 root-knot nematode eggs or juveniles in separate Petri dishes showed that all the different concentrations had toxic effects on eggs and juveniles of root-knot nematode. Egg hatch inhibition and juvenile mortality increased with increased concentration of the extracts. With an increase in exposure time, juvenile mortality increased. In potted plant studies, crude castor bean aqueous extracts and its lower concentrations of 20, 40 and 60% caused significant improvement in plant growth measures such as height and fresh shoot weight over the water blank control. The crude castor bean extract was nematotoxic to root -knot nematodes in vitro and in potted-tomato plants, but this was not demonstrated in field studies. Further work needs to be done before a firm recommendation can be made. INTRODUCTION Tomato (Solanum lycopersicum L.) is the most important vegetable in Ghana (Norman, 1992). It is also a fairly important cash crop in the outskirts of urban areas in the forest zone, in the Greater Accra area, Akumadan, Wenchi, and Mankesim (Obeng-Ofori et al., 2007). In spite of the importance of the crop, yields are usually low and sometimes total crop failure is recorded due to diseases, pest and other environmental factors. Root-knot nematodes attack on tomato is very common and is one of the factors responsible for the frequent failure of the crop (Norman, 1992). According to Hemeng (1981), a yield loss of 73-100% as a result of root-knot nematodes infestation in tomato occurred in Northern Ghana. As a result of their ability to attack most crops, root-knot nematodes are liable to cause losses wherever there is intensive cultivation of susceptible crops, and where precautions against population build up is not taken. © 2013 Kwame Nkrumah University of Science and Technology (KNUST) Journal of Science and Technology, Vol. 33, No. 1 (2013), pp1-11 1