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ŠUMARSKI LIST 3-4/1965 str. 11     <-- 11 -->        PDF

These data abouth the eonymph numbers show that the infestation by the Oak
Sawfly was very severe and that it culminated in 1960. Therefore the drop in increment
in this year can surely be attributed to this insect pest to a large degree.

In the year following (1961) there was no infestation by insect pests. So for instance
no more Oak Leafroller or Brown-Tail Moth was noticed, while the infestation
by the Oak Processionary Moth and Oak Sawfly was small. It is probable that —
4 years after the chemical insecticidal treatment of these forests — the parasites propagated
to such an extent that they liquidated at least some of the overpcpulated
insect pests. However, since 1962 other insects species have been noticed in higher
numbers, especially Operophtera brumata, Hibernia dcfoliaria, Biston ssp., Himcra
pennaria and others. All the above-mentioned were joined by the Gipsy Moth again.
In 1962 and 1963 it was hardly possible to notice this insect pest. Its potentiality of
propagation, however, is very high. Judging by the numbers of deposited egg clusters
in the autumn 1964, the Gipsy Moth is again in a phase of large population built-up
preceding the mass autbreak. If in the spring 1S65 one does not undertake a control
of caterpillars, enormous damages in the Lipovljani forests will occur again.