Effect of certain traditional cultural practices for the management of blast disease of rice in Manipur agro-climatic conditions

Abstract

Field experiments were conducted during kharif 2010 and 2011 seasons to ascertain the effect of various traditional cultural practices for the management of blast disease of rice (variety RCM10). Cultural practices viz. sowing method, sowing dates and weeding frequencies were considered. Among the treatments, timely transplanting reduces the disease parameters such as disease incidence, disease severity, AUDPC and rate of infection as compared to broadcasting method. However, no significant effect of seed sowing method was observed. Clean cultivation with three or more weeding showed relatively less disease parameters. Index Terms: Blast, rice, broadcasting, transplantation, sowing date, weeding, traditional. I. Introduction Rice is the most important staple food of Manipur. In north-east India, cultivated mostly under rain fed conditions during kharif season as both dry land and wetland crop. Blast disease of rice caused by Pyricularia grisea (Cook) Sacc. is one of the most widely distributed foliar disease of rice cultivated under upland and wetland systems as in other parts of the globe where rice is grown (Singh, 2005) (5). It occurs every year under the agro-climatic conditions (temperature, relative humidity, rainfall) of Manipur in mild or severe form. As the use of costly chemical fungicides for the control of blast disease has many harmful effects to the environment. Cultural practices practiced by the traditional rice farmers provide a scope for the economically and eco-friendly management of the disease without affecting the environment. As such these practices reduce the use of synthetic chemicals for the control of the disease to some extent although it is a labour intensive. Therefore an attempt has been made to ascertain the effect of the cultural practices for the management of blast disease of rice under the prevailing climatic conditions of Manipur with an objective of encouraging traditional rice farmers for improvement of eco-friendly practices and refraining them from the use of chemicals. The objective of the present study is to enhance knowledge to the poor and marginal farmers in understanding various eco-friendly management practices which are simple and affordable. II. Materials And Methods Field trials were carried out during kharif seasons (2010 and 2011) in a sick farmer's field which shows the occurrence of blast disease of rice during the last three years of cropping seasons. The experiment was laid out in a randomized block design in 3 × 3 m 2 plots with three replications for each treatment. A higher dose of nitrogenous fertilizer @ 100kg/ha as against the recommended dose (60 kg/ha) was applied to make the crop more prone to disease. Traditional cultural practices such as sowing method (broadcasting and transplanting), sowing dates (15 th June, 30 th June and 15 th July) and weeding (one time weeding, two times weeding and three times weeding) were considered to see their effects on the epidemiology of blast disease of rice. Seed broadcasting and nursery planting (25 days old seedlings were transplanted in the field @ 2-3 plants per hill at a spacing of 20 cm row to row and 15 cm plant to plant) for transplanting treatment were done on the same day. For sowing dates, the seed nurseries were raised keeping 15 days of interval and transplanted to the field keeping the same interval. Hand weeding was done after 20 days of transplantation and subsequent weeding was done at 15 days interval. The disease parameters like percent disease incidence (D.I. %) and percent disease severity (D.S. %) were observed at fortnightly intervals starting from the occurrence of the disease till the flowering stage of the plant. Data on D.I.(%), D.S.(%), the area under disease progress curve (AUDPC) and apparent rate of disease infection (r) were using simple random sampling and calculated as follows.