Prevalence of plant parasitic nematodes associated with rice in Ghana witha discussion of their importance

A survey of plant parasitic nematodes of rice was made in Ghana between 199 4-1997. Fifty-one species in 29 genera were found in 145 fields from upland , hydromorphic, rainfed lowland and irrigated lowland ecosystems in the sav annah and forest agroecological zones. Eighteen species were endoparasites of roots. In upland/hydromorphic rice fields in the savannah zone Pratylenc hus spp. (80% of fields) and an undescribed species of Ditylenchus (78%) we re most prevalent, whilst Coslenchus franklinae (84%) and Helicotylenchus s pp. (76%) were most prevalent in the forest zone fields. Maximum population densities encountered were 960 C. franklinae per 100 mi soil and 700 Dityl enchus n. sp. per g root. In the savannah zone Hirschmanniella spp. (100%) were more prevalent than other nematodes in lowland rice, but in the forest zone Xiphinema bergeri (71%) was the most prevalent nematode in lowland ri ce. Occurrence of nematode species was different in different agroecologica l zones and rice ecosystems. There was no relationship between rice plant h eight and nematode population densities in crops close to harvest time in u pland/hydromorphic fields in the savannah zone.