Epidemiology and Control of Bacterial Leaf Blight of Rice

INTRODucnoN The bacterial leaf blight disease of rice was first observed in the latter part of the last century in various localities of southern Japan. Severe dam­ age has been caused annually since then. Scant information is available on the occurrence of this disease in other countries. It has been reported in Korea (105), Taiwan (21), the Philippines (15-17, 19, 77), Indonesia (15, 16), Thailand (19), India (5,84,86-88 ), and China (8 ,9 ,107). According to investigations carried out in recent years (59, 66, 119), the disease has become of economic importance in many other countries of Asia, namely Ceylon, Cambodia, and Malaysia. It occasionally causes severe damage to rice yields and is recognized as one of the most important diseases of rice growing areas in Asian countries. No reports of the presence of the disease in America, Australia, Africa, and European countries growing rice have been received. Possibly the disease is nonexistent in these countries or is not of any great importance. Early investiga tions during 190 8 to 1910 indicated that bacterial blight occurred in almost all southwestern prefectures of Japan (73, 79, 104). It gradually spread to northern Japan and in 1962 was observed in Hokkaido. At present, the disease is widespread in all prefectures of Japan, although its severity and damage is limited in the north. The acreage infected by leaf blight disease was 50,000 to 60,000 hectares in 1940, exceeded 100,000 hec­ tares durin g the Second World War, and is now 300,000 to 500,000 hect ares. This corresponds approximately to 10 per cent of the total rice area in Japan.