Potential Relationship between the Imissions an the Occurrence of Some Insect Pests

1991

S. 571-576

4 Lit. Ang.

Unselbständiges Werk

200062024

Some insect species occur on a calamity scale from time to time in all regions of Europe. These calamities depend on both biotic and abiotic factors. In the past twenty years, another factor has occurred: the combined effect of immissions and acid rains. This study is focused on the problem of calamity occurrence of several pests in relation to the problem of immissions in the Czechoslovak territory. These species are: Ips typographus, Zeiraphera diniana, Cephalcia abietis and Pristiphora abietina; some species propagated on newly planted Betula and Sorbus in places where spruce had been felled. The survey of distribution of Ips typhographus (1982- 1986) is shown in Fig.2. The most severely invaded regions are in North Bohemis along the Polish border, in North Moravia, and in South Bohemia along the border with Austria. It is mainly in the north of Bohemia that the forest stands were severely affected by immissions (Fig.1). The assumption that the stands affected by industrial immissions would not be invaded by the spruce bark beetle has been found not to be right. Zeiraphera diniana Gn. - this species gradated in northeastern and northwestern Bohemia in 1977- 1983: the gradation occurred again in areas most severely affected by immissions. Pristiphora abietina Christ and Cephalcia abietis L. - the noxious effect of the occurrence of the species Pristiphora abietina is shown in Fig.3. It can be read from the map that there is a correlation between the imissions and the noxious occurrence of this species. The northern part of Bohemia and Moravia is much more severely invaded than the southern part, where the immission load is much smaller. At present, there is no evidence to prove a relationship between the imissions and the occurrence of Cephalcia abietis. However, what is interesting is the fact that the species Cephalcia falleni Dalman. has spread southwards from Poland to Moravia. The pests of the replacer pests - the harmful species Erannis defoliaria (Clerck) and Operophtera brumata L. occurred in the areas where spruce had originally been grown. The occurrence of these species coincides with the highest levels of imissions in northwestern Bohemia. It was necessary in these areas to treat the stands chemically in areas of 3500- 500ha.