Effect of agro-ecosystem on the occurrence of the rice root-knot nematode Meloidogyne graminicola on rice in Myanmar

Abstract

Two surveys were carried out during 2009. The first survey was during the dry summer season (mid-January to mid-May) in 450 rice fields from ten regions representing the summer-irrigated, lowland rice ecosystem in the lower Ayeyarwady delta area of Myanmar. The second survey was during the rainy (monsoon) season (mid-May to mid-October) in 102 rice fields from three regions representing the rainfed upland rice ecosystem in the northern hilly area of Myanmar. Soil and root samples were collected from 552 rice fields from 15 locally cultivated rice varieties in lowland and upland rice ecosystems. The frequency of occurrence of Meloidogyne graminicola was significantly (P < 0.05) higher in the lowland compared with the upland rice ecosystem (78 vs 9%, respectively). On average, both the population density and the root galling index of M. graminicola in the lowland rice (289 J2/g root and 4.1, respectively) were significantly (p < 0.05) higher than in the upland rice (4 J2/g root and 1.2, respectively). In lowland rice, the frequency of occurrence of M. graminicola was significantly (p < 0.05) higher in the delayed irrigation compared with the early irrigation (87 vs 54%, respectively). Similarly, both the average nematode population density and mean galling index in delayed irrigation (347 J2/g root and 4.5, respectively) were significantly (p < 0.05) higher than in early irrigation (46 J2/g root and 1.2, respectively). M. graminicola is the major pest of the summer-irrigated, lowland rice ecosystem in Myanmar. Further research is needed for development of integrated pest management technologies to maintain a profitable rice industry in Myanmar.