Abstract
Myriophyllum aquaticum is an invasive alien aquatic plant and causes many problems such as water pollution, elimination of native plants, and obstructs water ways. To prevent these problems, suppression of M. aquaticum has been often implemented by local governments and/or NPOs. However M. aquaticum regenerate rapidly and suppression is not effective. In this study, to establish a method for eradicating M. aquaticum, vegetation and population surveys and test extermination were carried out in the field, and shading experiment took place in the laboratory. M. aquaticum covered the whole of the pond, but it rooted only on the shallow area near the waterside. During the laboratory shading experiment, M. aquaticum individuals survived the darkness for 158 days, but the length of M. aquaticum stems decreased through that period. It suggests that shorter fragments of M. aquaticum can die by short periods of darkness. At test extermination in the field, M. aquaticum did not regenerate after shading treatment with soil removed. Most fragments of M. aquaticum were removed with soil, and remnants of fragments were killed by the long darkness period. Exterminating M. aquaticum might be possible by using shading together with removing soil.
