稲萎縮病の生態および防除に関する研究 第15報 本病の発病と肥料との関係(2)

抄録

1. Rice plants were grown on field plots, in which 0.5-3.0kg of nitrogen per are was applied except in check plots, in 1962 and 1963. The plants were infected under natural conditions with dwarf disease. The more were the amounts of nitrogen, the severer the disease occurrence.
2. Rice plant were grown on 1/5000 α Wagner's pots in which 0.2, 0.5 and 1.0 gm of nitrogen per pot was spplicd. The plants were infested at 14-or 16-leaf stage with viruliferous green rice leafhoppers (Nephotittix cincticeps Uhler) that had reared on dwarf-affected rice plants. High nitrogen plants proved to be more susceptible to the disease than low nitrogen plants, at the late leaf age. When the plants were at 14-leaf stage, symptoms developed on plants to which 0.5 and 1.0 gm of nitrogen was applied. Degree of symptom development was much severer on the latter. No symptom developed on plants to which 0. 2 gm of nitrogen was applied. When the plants were at 16-leaf stage, symtoms developed only on plants to which 1.0 gm of nitrogen was applied.
3. Leaves were detached from rice seedlings grown in diffent amounts of nitrogen, and then were covered by single cage. Rice green leafhoppers were allowed to feed on caged leaves for 24 hours. Leafhoppers were attracted toward the leaves of high nitrogen level. At certain plant-age, the number of infesting viruliferous leafhoppers per plant influences the percentage of infection.