Abstract

This study was conducted to determine the occurrence levels of Quamoclit coccinea in South Korea's Jeonnam province and to better understand how the densities of Q. coccinea contribute to yield reduction in soybean crops. In 2016, Q. coccinea had an occurrence rate of 8.45% in 71 farmlands across Jeonnam province. In 2017, however, the Q. coccinea occurrence rate had risen to 45.7% in 35 farmlands across Jeonnam province. Although Q. coccinea growth rate and seed production varied significantly from region to region, in this study we observed Q. coccinea growing rapidly over short periods of time and posing a significant threat to soybean crops. Compared with the control, soybean shoot fresh weight was reduced by 12, 23, 37 and 45% in crops with Q. coccinea densities of 1, 5, 10 and 20 plants per m2, respectively. Soybean yields were reduced by 30, 69, 80 and 92% in crops with Q. coccinea densities of 1, 5, 10 and 20 plants per m2, respectively. Soybean crops impacted by Q. coccinea also had notably reduced yield components such as pod numbers, 100-weight and ripening rates. Our study clearly showed Q. coccinea capacity for destruction in soybean crops, however, further studies are needed in order to determine how to best combat this troublesome weed species and prevent it from spreading further.