Abstract
This paper dealt with the results of writer's investigation of the relation of environ-mental factors and age of Ladino clover plants, Trifolium repens L., to occurrence of Curvularia leafspot of Ladino clover caused by Curvularia trifolii (KAUFF.) BOEDIJN. The spore germination of the causal fungus was shown between 15℃ and 37.5℃ and the optimum temperature was 30℃. The mycelial growth of the causal fungus on the culture medium was shown between 15℃ and 35℃ and optimum temperature was 27.5℃. The spore germination and the mycelial growth were almost not effected by the light. The disease was occurred at a wide range between 15℃ and 38℃ and the occurrence was severe at 25℃ to 30℃. The infection was accelerated under dark condition. The severity of the disease was increased by keeping the plants in high air humidity one to two days before inoculation. Ladino clover plants developed newly at 20℃ and 25℃ after defoliation were shown higher severity of the disease than that developed at 10℃. The severity of the disease in seedlings increased with the progress of growth stage untill seven to eight leave stages. In green house test, the severity of the disease was higher on young leaves than on older leaves in the adult plants. But little difference was shown in the severity of the disease depending on the age of stand of the plants.
