. TOMATO ROOTS

The potrential for nematicidal actjvity in indigenous plant materials or byproducts of the food or oil industries, as possible substitutes for conventional nematicides, has been investigated by many research workers. One of the more common essences suggested is neem (Azadirachta indica A. Juss.). There is subs-tant.ia1 evidences tha t neem leaves (Egunjobi & Afolami, 1976; Saxena, Chhabra & Jasial, 1977) and neem oil cake (Sitaramaiah & Singh, 1978; Vijayalak-shmi & Prasad, 1979) contain effective nematicidal substances. The present research was done to compare the effects of seed extracts of neem and t>wo african essences Hannoa undula ta (Guill. Perr.) Planch. and Hannoa Kla ineana Planch. on the penetration of Meloidogyne jaoanica juveniles into tomato roots. Seed extracts were prepared as follows:- Crude powders of neem, H. undulata and H. k la ineana were prepared by shelling almonds, cutting them into pieces and grinding in 5 cm3 of distilled water for 5 mm in a Potter tissues grinder (1 500 R/mn) the quantities necessary to prepare suspensions in concentrations of 400, 800, 2 000, 4 000,20 O00 and 40 O00 ppm.- Delipidified powders of the three essences were obtained by extracting lipids of ground almonds with hexane in a Soxhlet apparatus (Polonsky & Bourguignon-Zylber, 1965). Each suspension wa