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 differed in cropping intensity, in Ùlree agroecological zones of Ivory Coast. Eighty nematode species from 35 genera were found associated with rice. Population densities of Helicorylenchus spp. were significantly lower in long fallows in the forest zone, but the mean population densities of ail other nematode genera and species did not differ significantly between fallow regimes in any of the three agroecologies. Mean nematode population densities exhibited a trend, decreasing, under longer fallows in the forest and savannah zones. Nematode diversity was greatest in the forest-savannah, decreased in the savannah and was least in the humid forest. The population densi!)' and prevalence of sorne nematode genera differed between agroecologies. Of the known pests of rice, Mewidogyne spp. were most prevalent in the forest, whilst Pralylenchus spp. were more prevalent in the forest-savannah and savannah. Helerodera spp. occurred in the forest and forest-savannah, but its prevalence was low. © OrstomlElsevier, Paris