Wheat yellow mosaic is a soil-borne virus disease caused by wheat yellow mosaic virus (WYMV), which is transmitted by soil inhabitant Polymyxa graminis. It was first reported in Japan in the Taisho era. With the increase of land used for domestic wheat production, outbreaks of this disease occurred in the 1990s in Japanese wheat production areas. The breakdown of resistance also occurred, and the disease has become an obstacle to increased wheat production in Japan. Countermeasures to this disease have been restricted to changes in cultural practices and the use of resistant cultivars. On the other hand, because of the lack of an experimental inoculation system, the mechanism of cultural practices to control this disease were not clarified, and the relationship between WYMV strains and the resistance of wheat cultivars to the virus were not clear. This study was conducted to contribute to the development of resistant cultivars and practical cultural practices to control wheat yellow mosaic disease. For this purpose, the ecology of this disease was clarified from the aspects of the effect of temperature on the disease. The favorable temperature for the virus to propagate in the wheat plants is about 10℃, while 5-10℃ is favorable to disease progression. Masking of the symptoms occurred when the temperature was above 10℃, and then the wheat plant recovered from the disease. The favorable temperature for the infection of P. graminis ranges from 13℃ to 15℃. Based on this knowledge, we have clarified why late sowing is an effective disease control measure for this disease. An experimental inoculation system that consistently had high inoculation efficiency was also developed.