2009.08.08: Austria, Vienna XXII. district, 155 m AMSL, growing on badly damaged Populus sp.(near creek - Hausgraben). Of course mistletoe isn't the main or primary reason for trees dying but they help the process along. My guess would be that this poplar won't last very long, probably a couple of years. The tree could be either Populus nigra or one of its hybrids, P. × canescens and - as suggested below by Sciadopitys - P. × canadensis, especially as it is true that the hybrid P. × canadensis is particularly often host of Viscum - however, I've also seen plenty of P. nigra bearing V. album. Both species are common. German name: Laubholz-Mistel.