Field surveys and experiments were undertaken in rice and wheat from 1993 to 1995 to understand the association of plant parasitic nematodes with rice-wheat ecosystems and the effect of cultural management practices on nematode incidence and activity. Four genera of plant parasitic nematodes were observed in lowland rice, of which the rice root nematode (RRN, Hirschmanniella mucronata and H. oryzae) and root knot nematode (Meloidogyne spp.) were observed both in roots and soil with varied frequencies and population densities. Tylenchorhynchus and Hemicycliophora were observed only in rice soils at low densities. In farmers' fields in Rupandehi District, a significantly higher RRN, population was observed in irrigation fields managed by extension. Of the farmers' fields managed by extension, canal-irrigated fields had significantly higher nematode populations compared to rainfed fields. Fields irrigated by shallow tubewell had significantly higher nematode populations than those irrigated by deep tubewells. Significantly higher numbers of Hirschmanniella spp. were observed in fields under double crops of rice compared to fields with single crops of rice. When rice was grown after different winter crops, RRN was the only nematode observed, and populations of this nematode were significantly higher in rice grown after fallow, lentils, and broadleaf mustard, Significantly lower RRN populations were observed in plots grown after wheat, linseed, broad beans, mustard, and chickpeas. RRN was the only nematode observed in the soils of these winter crops but not in the roots. These crops are not hosts of this nematode, which was carried through the soil from one crop of rice to the next.

English

9901|AGRIS 9901|R98-99NOTCIM

Jose Juan Caballero

CIMMYT Publications Collection