In Japan, the spread of morning glory (Ipomoea spp.) in soybean fields has become a serious problem. The aims of this study were to elucidate the biological characteristics of red morning glory (I. coccinea L.) and pitted morning glory (I. lacunosa L.) as well as to investigate the control effects of an application system with fluthiacet-methyl and imazamox ammonium salt. Field experiments were conducted from 2019 to 2020 in Higashi-Hiroshima city, Hiroshima Pref., Japan. The cumulative emergence rate of the pitted morning glory increased earlier than that of the red morning glory. The cumulative emergence rate of the red morning glory and the pitted morning glory reached 90% at 16 to 27 days and 10 to 14 days after soybean sowing, respectively. In addition, for the pitted morning glory, the rate of leaf age development was higher than that of the red morning glory. The morning glory vines also developed earlier, and the initial growth tended to occur earlier in the season than in the red morning glory. In the application plots for the selective post-emergence herbicides, a negative correlation was found between dry matter weight of the pitted morning glory and the number of soybean seedlings. In contrast, a positive correlation was found between the dry matter weight of the pitted morning glory and the relative photosynthetic photon flux density in the soybean canopy. Therefore, to enhance the control effect of the pitted morning glory by selective post-emergence herbicides, it is important to increase the number of soybean seedlings and the effect of shade by promoting soybean growth.

In Kyoto Prefecture, Physalis angulata L. var. angulata and P. angulata var. lanceifolia (Nees) Waterfall spread rapidly in the red beans fields and cause a reduction in its yield and quality. We studied the effect of light, temperature, and chilling treatment on seed germination of the two Physalis spp. obtained from a red bean field. The germination rate of fresh seeds of P. angulata var. lanceifolia was 15% or higher at alternating temperatures of 25/15°C, 30/20°C, and 35/25°C under both light and dark conditions, whereas that of P. angulata var. angulata was less than 5%. Furthermore, the germination rate of P. angulata var. lanceifolia seeds stored in the open air was less than 5% under dark condition and constant temperature condition. However, the germination rate of P. angulata var. angulata seeds stored in the open air was 28.9% to 93.3% at alternating temperatures of 25/15°C, 30/20°C, and 35/25°C, and 6.6% to 92% at constant temperatures of 20°C, 25°C, and 30°C. Following chilling treatment under light conditions and dark and wet conditions, P. angulata var. angulata seeds exhibited higher germination rates than P. angulata var. lanceifolia. This shows that the environmental requirements for dormancy release after seed dispersal of the two species are different.