Bedeutung der sekundären Kiefernschädlinge in Gebieten chronischer Einwirkung industrieller Luftverunreinigungen

The Economic Importance of Secondary Noxious Insects of Pine on Territories with Chronic Influence of Industrial Air Pollution

Wien

1972

Unselbständiges Werk

673

200144693

In pine stands under chronic influence of industrial air pollution, insects counted by foresters in the group of so-called 'secondary noxious insects' are of great economic importance. They kill trees weakened by the influence of industrial emissions and sometimes by parasitic fungi and feedings of Exoteleia dodecella L. The species composition of noxious insects is dependent to a high degree on the stand density and the intensity of their penetration by industrial gases and smokes. In stands with gaps, and those strongly ty thinned, the following insects occur most frequently: Phaenops cyanea F., Pissodes piniphilus Hbst. and Siricidae. Sometimes, they are accompanied by large numbers of other noxious insect species, under normal conditions considered to be of tertiary economic importance. They attack most of all the top and middle parts of trees, causing so-called 'industrial clearings', and they speed up the process of so-called 'recession of the forest'. In denser and more shaded stands, the following insects occur most often, both in frequency and density: Myelophilus piniperda L., Acanthocinus aedilis L., Trypodendron lineatum OL, and Pissodes piniphilus Hbst., and locally also Ips acuminatus Gyll., Myelophilus minor Htg. etc. These noxious insects thin stands further away from the sources of air pollution, causing thus more intensive penetration of industrial gases and smokes into these stands and increasing the weakening of trees which are afterwards attacked by insects belonging to the first group.