Hirschmanniella spp. in Rice Fields of Vietnam

Root and soil samples from one-crop and two-crop rice fields were collected in a survey for Hirschmanniella spp. in Vietnam during 1978-80. Hirschmanniella spp. were found in 50-78% of the soil samples and 98-100% of the root samples collected. Population densities of nematodes in root systems were lowest at posttransplanting and highest at heading time. Numbers of nematodes inside roots increased 20-22 times from transplanting to heading in fields with both crop sequences. Population densities of Hirschmanniella spp. in two-crop rice fields were more than twice those in one-crop rice fields.