ECOLOGY AND PATHOGENICITY OF THE HOPLOLAIMIDAE (NEMATA) FROM THE SAHELIAN ZONE OF WEST-AFRICA .6. HOPLOLAIMUS-PARAROBUSTUS (SCHUURMANS STEKHOVEN AND TEUNISSEN, 1938) SHER, 1963 AND COMPARISON WITH HOPLOLAIMUS-SEINHORSTI LUC, 1958

The geographical distribution, population dynamics and vertical distri bution in the soil were studied for the nematode Hoplolaimus pararobus tus. The factors influencing the multiplication and survival rates of H. pararobustus and H. seinhorsti were studied in the laboratory. Both species appeared adapted to the ecological conditions of the semi-ari d tropics of West Africa. The absence of H. seinhorsti from these ecol ogical zones remains unexplained; the possibility of the loss of repro duction capacity after anhydrobiosis is suggested A the inoculum level s tested, these two species did not have any pathogenic effects on the plants with the exception of H. pararobustus which induced a reductio n of root fresh weight for cowpea.