Population dynamics of the rice root nematode Hirschmanniella oryzae on monsoon rice in Myanmar

Abstract

Soil and root samples of the short crop cycle duration rice variety Yadanartoe were collected at 10-days intervals, starting at 20 days after transplanting until 20 days after harvest, from September 2008 until January 2009, to study the population dynamics of Hirschmanniella oryzae on (rainfed) monsoon rice. Plant growth stages, the ambient air and soil temperature, rainfall and relative humidity during the sampling period were noted. The soil type is clay and has a pH of 5.1. In the roots, three nematode population density peaks were observed during the sampling period: at the maximum tillering stage, at the milky grain stage, and between harvest and 10 days after harvest. The highest peak (483 H. oryzae/g roots) was observed at the milky grain stage. The lowest root population density (46 H. oryzae/g roots) was found at harvesting. Population densities in the soil followed more or less the same trend as in the roots. After harvesting, the soil population density increased. During our observation, we did not find any effects of environmental conditions on the population densities of H. oryzae. However, it was found that the population dynamics of H. oryzae were influenced by the plant growth stage.