Aktuelle Schäden an Bäumen im Stadtbereich

Wien

2005

S. 2-6

10 Abb.

Artikel aus einer ZeitschriftUnselbständiges Werk

200127841

Despite cold and wet weather conditions all kinds of defoliators, especially winter moths (Operophtera spp., Erannis defoliaria) played an important role on Oak, Hornbeam, Ash, Lime, Maple and Beech in the cities. Many trees were completely defoliated, but in early summer new leaves were built and practically no damage was observed. For the first time an increase of the Pod gall midge (Dasyneura gleditsiae) could be observed on Honey locust in Vienna and Baden (near Vienna). The larvae of Dasyneura gleditsiae are sucking on developing leaf and due to the feeding the leaflets will turn into pod like galls. The damage of a heavily infested tree looks quite remarkable but has no economic impact. Another insect, the Sycamore lace bug (Corytucha ciliata) found its way to the eastern part of Austria and occurs regionally in high densities. Severe infestations could only be observed on old Sycamore (plane trees) due to the overwintering of the bugs in cracks and under the bark. The damage, a characteristic yellowing of the leaves, is, not dangerous for the tree, even if it reaches a certain degree. For some years there has been a significant increase of bark beetles in urban areas, parks and private gardens, especially in coniferous trees. Remarkable was the occurrence of Ips typographus and Pityogenes chalcographus infesting spruce, but also bark beetles on Thuja sp. and other cupressaceous. Jewel beetles (Buprestids) play an important role when they are infesting fresh planted trees. Especially Lime and Maples are endangered. These mostly 5 - 11 millimetres long, metallic shining beetles prefer sunlit or damaged parts of the bark. Beech splendour beetle (Agrilus viridis) and Linden burncow (Lampra rutilans) were often recorded, but only sometimes a small buprestid on Lime tree. Other different species were found on Horse chestnut, Willow and White beam. The populations of some leaf miners have been increasing since 2003. The Horse chestnut leaf miner (Cameraria ohridella) and Sycamore leaf miner (Phyllonorycter platani) were the most frequent species. Against the mainstream the two leaf miners of Black locust, Phyllonorycter robiniella and Parectopa robiniella have rarely been found since the last two years, although they have well been distributed all over the eastern part of Austria. The first records of Lime leaf miner (Phyllonorycter issikii) in 2002 and 2003 could not be confirmed, despite intensive search. Numerous leaf diseases, due to the wet weather conditions in 2005, were found on nearly all trees in urban areas. Remarkably, Poplar leaf rust (Melampsora spp.) was observed on different poplars, Guinardia-leaf blotch (Guignardia aesculi) on Horse chestnut and Sycamore leaf disease (Apiognomonia veneta) on Sycamore. In many parts of the country, in urban areas as well as along motorways, many tree species were damaged by road salt. Mostly affected were Horse chestnut, Ash and different Maples.