PLANT-PARASITIC NEMATODE DIVERSITY AND PREVALENCE IN TRADITIONAL UPLAND RICE IN IVORY-COAST - PRELIMINARY-OBSERVATIONS ON THE EFFECTS OF CROPPING INTENSIFICATION

This study compares nematode prevalence in upland rice fields, which d iffered in cropping intensity, in three agroecological zones of Ivory Coast. Eighty nematode species from 35 genera were found associated wi th rice. Population densities of Helicotylenchus spp. were significant ly lower in long fallows in the forest zone, but the mean population d ensities of all other nematode genera and species did not differ signi ficantly between fallow regimes in any of the three agroecologies. Mea n nematode population densities exhibited a trend, decreasing, under l onger fallows in the forest and savannah zones. Nematode diversity was greatest in the forest-savannah, decreased in the savannah and was le ast in the humid forest. The population density and prevalence of some nematode genera differed between agroecologies. Of the known pests of rice, Meloidogyne spp. were most prevalent in the forest, whilst Prat ylenchus spp. were more prevalent in the forest-savannah and savannah. Heterodera spp. occurred in the forest and forest-savannah, but its p revalence was low. (C) Orstom/Elsevier, Paris.