With the prevailing weather likely to cause an outbreak of rice blast disease, the Agriculture Department has issued advisory to farmers in the district to take prompt measures if symptoms of the disease manifest in the samba paddy crop.
Given the experience over the past few years, when the blast disease adversely affected yield, the department advised farmers to opt for disease-resistant varieties and avoid cultivation of highly susceptible varieties such as improved white Ponni and BPT-5204 (Andhra Ponni). However, a large number of farmers have raised Andhra Ponni as the variety is in good demand among traders and fetches a better price than others.
“Rice blast is a common but important fungal disease of rice. The disease is caused by the fungus, pyricularia oryzae , which attacks the rice crop at all stages. The symptoms can be seen on leaves, nodes, neck of panicle, and on grains,” said S. M. Uduman Mohideen, Joint Director of Agriculture, in an advisory.
Symptoms
On the leaves, the lesions start as small water-soaked bluish green flecks and soon enlarge and form characteristic spindle-shaped or eye-shaped spots with grey centre and dark brown margin (leaf blast). The elongated spots join together as the disease progresses, and large areas of the leaves dry up and wither. Similar spots also form on the sheath. Severely infected nursery and field present a burnt appearance. Subsequently, node blast and neck (panicle) blast occur. The disease causes heavy economical loss to rice farmers and the symptoms normally occur during the winter months of December and January. Blast-infected grains become poorly filled and chaffy. Dark spots may be formed on the grains also and reduce the quality of the grain, Mr.Mohideen said.
Application of excessive doses of nitrogenous fertilizers, intermittent drizzle, cloudy weather, high relative humidity, long dew periods and low night temperature make situation conducive for the disease. Spraying pseudomonas fluorescens (5 gm/litre three times from 45 days at an interval of 10 days) will control the disease. Chemical control involves spraying of Tricyclazole (200 grams an acre), or a combination of Tricyclazole and Mancozeb (400 grams an acre), or Azoxystrobin (200 ml and acre). The fungicides should be sprayed before 11 a.m. or after 3 p.m. in the afternoon, the department advisory said.
Speaking to The Hindu , Mr.Mohideen, however, said the advisory had been issued as a precautionary measure so that farmers could initiate the control measures immediately when symptoms appear on their field.
“Otherwise, the disease can spread quickly. So far, there has been no report of the disease outbreak in the district,” Mr. Mohideen said.
