A Rice Nematode Disease \u22Senchu Shingare Byo\u22 : Ⅰ. Symptom and Pathogenic Nematode

Since more than ten years past a rice disease with bleached-tip of leaves has come to attention in Kyushu. The disease is observed both in upland and watered field. The bleached-tip symptom appears usually after the beginning of elongation growth. The tip of leaf about 2 to 5 cm. in length becomes pale yellowish green to white or transparent. Later the discolored part becomes brownish and is torn off. The affected leaf is considerably shortened and usually twisted at its apical portion. Commonly, the leaves with bleached-tips or white-tips are situated alternately on a stem. Sometimes, however, the bleached-tip symptoms are invisible on the whole leaves of affected plants. In paddy field in Kyushu, it is inferred that about three times of the numbers of stems with white-tips are affected by the pathogen. The affected plants are usually stunted, and have many tillers with dark green colored leaves. The tillers from higher nodes are often observed. The length of ear of the affected plants is reduced, unhulledgrain becomes slender, the percentage of fragmental grain is increased. Ten to thirty per cent decrease in yield is inferred. The present disease spreads widely in Japan, from Hokkaido to Kyushu. The causal nematode, Aphelenchoides oryzae Yokoo, is characteristic in having star shaped, trifurcated mucro at its tail end, and in bending habit of tail end in male when killed by heat. Diagnosis of the present nematode is given