A survey of plant – parasitic nematodes associated with economic crops was carried out from April 2002 to April 2003 in Myanmar. Seventeen different genera of plant – parasitic nematodes,including new report of species for Myanmar, were observed from 17 different crops in 11 different sites. From the survey, rice root – rot disease caused by Hirschmanniella oryzae was found to be severe in rice nursery fields of YAU and CARI campuses, Yezin. Investigations were thus made to examine the reaction of six rice varieties against root – rot disease caused by H. oryzae, and also to observe the effect of different nitrogen rates on plant growth and population of H. oryzae. It was observed that the number of nematodes was increased with an increase in nitrogen up to 84 kg N/ha, and it became decreased at 112 kg N/ha.