Effects of Ufra Disease on Yield Loss of Deepwater Rice in Bangladesh

Abstract

Abstract Ufra, caused by the stem nematode, Ditylenchus angustus (Butler, 1913) Filipjev, 1936, is a serious disease of deepwater rice in southern Bangladesh. It was studied between 1977 and 1979 as part of a joint project with the Overseas Development Administration at the Bangladesh Rice Research Institute. Three symptom types are distinguished according to the extent of panicle emergence: Ufra1 (none), Ufra2 (partial) and Ufra3 (complete). All three represent total loss from that panicle. The number of Ufra2 as a percentage of the total number of panicles present in a specified area is selected as a disease index (UfraII). A function relating yield to the level of UfraII is proposed on the basis of selective samples from a field with a well-defined ufra patch. This function is compared with another derived from random samples in different fields along a linear transect through an area where ufra is endemic. Loss of panicle density, i.e. panicles/m2, is identified as a major component of yield loss, app...