Notes on the occurrence of Phytolacca americana L. in crop fields and its potential agricultural impact

Phytolacca americana is a large perennial invasive alien plant indigenous to the eastern United States. In Europe, it usually infests forest edges, open woodlands and other disturbed habitats. In this study, the occurrence of the species as a weed in crop fields in Austria was analysed based on distribution data collected from different sources. Moreover, P. americana was surveyed in a selected area in southern Austria (Styria) and its behaviour as weed was analysed by phytosociological releves. The situation of the species in Austrian neighboring countries (the Czech Republic, Germany, Hungary, Italy, Slovakia, Slovenia, Switzerland) was also briefly investigated. The results show that P. americana is generally rare on arable land in Austria and its neighboring countries. The survey and distribution data collected, however, showed that P. americana occurred locally more abundant in crop fields. Two factors may have contributed to this phenomenon: (i) high propagule pressure from large forest and ruderal populations, (ii) and small-scale and less intensive cultivation practices (e.g. weed control) of particularly low growing crops such as oil pumpkin. The study illustrates the need to further monitor the occurrence of P. americana in crop fields and its potential impact.