Management of Sicyos angulatus in the Republic of Korea
Sicyos angulatus (Cucurbitaceae, EPPO A2 list) has spread across the Republic of Korea within the 15 years since its first appearance in 1989, covering now more than 110 ha (data obtained in summer 2005). Most populations were found on riversides, with a few cases in mountainous or agricultural fields. The plant has colonized the four major rivers of Korea; it is thought that new populations on riversides originate from seeds which are being carried by the river water. Successful colonization of S. angulatus was prominent on riversides with slow water flows and without an emergent plant belt. Heavy rains leading to soil erosion and floods amplify seed export greatly. Because fruits are spiny, humans and animals are efficient transporters of the seeds.
Plant growth was studied and a management scheme to suppress the plant has been proposed in the Republic of Korea. Massive germination can lead to a 100% cover of the soil layer during the growing season. Average and highest seed density at full maturation was 748 and 1128 seeds/m², respectively. A few seedlings/10 m² were enough to cover the whole grass mat by July. Results also showed that riversides with a well developed emergent macrophyte belt in water were free from S. angulatus. An emergent macrophyte belt composed of Typha angustifolia, Phragmites japonica and Phragmites communis could successfully prevent seeds of S. angulatus from accessing riversides. It was felt that aquatic plant belts could therefore be used as a management tool to prevent invasions. Routine management of riversides for landscaping will prevent colonization by S. angulatus while no special control is needed in fields because of the intensive agricultural practices. Moreover, S. angulatus, when submerged, goes into rapid lysis and extended submersion of invaded riversides or fields proved to be highly effective to control the plant. Ensuring that seed-free water drains from sites highly invaded and that large populations are destroyed before fruiting in watersheds upstream of rivers or lakes was recommended.
Sources
Kil JH, Kong HY, Koh KS, Kim JM (2006) Management of Sicyos angulata spread in Korea. In: Neobiota. From Ecology to Conservation. 4th European Conference on Biological Invasions. Vienna (Austria), 2006-09-27/29, BfN-Skripten 184: page 170.