prilagođeno pretraživanje po punom tekstu

ŠUMARSKI LIST 3-5/1991 str. 104     <-- 104 -->        PDF

The Elm-itree has disappeared from our forests due to the synchronized activity
of two biotic agents, the bark beetle (Scolytus spp.) and Duch eln>disease
(Ceratocystis ulmi Mor.) in unfavourable climatic conditions (drought). More intensive
dieback of the third dominant species in the lowland forests of Common
Ash, started in the 1943—47 period. Even then 50% of Common Ash trees perished
from dieback at some localities in Vinkovci. The Common Ash is threatened by
ash-tree borers (Steronychus flaxini Deg.). The ash-tree borer is present everywhere
as a species in Europe where the Ash-tree is found, but only in Yugoslavia
does it reach the stage of gradation, and it is therefore understandable that we
are a country with the most intensive process of Ash-tree dieback in Europe. The
Beech started to dieback as early as 1950. It is very susceptible to late spring
frost and drought, and is also attacked by bark cancer (Nectria ditissima Tul.).
The Beech is also attasked by a defoliator (Rhynchaenus fagi L.). In 1983 the
first dieback of the Sessile-tflowered Oak was registered. The causes were the
drought, severe attack of leaf-roll moth and emissions. The primary cause of the
dieback of the Sweet Chestnut since 1950 has been bark cancer (Cryphonectriaparasitica Barr.), and drought and emissions have an unfavourable effect. The
dieback of the Lime-trees is due to mednjača, (Armillaria mellea Wahl.), drought
and partial defoliation. Deciduous Oaks from the Adriatic region are endangered
by defoliation caused by the gipsy moth and leaf-rollers. The gipsy moth also
attacks the Evergreen Oak. Fir-tree, Spruce and pines in the continental area
perish due to emissions and drought. A question which remains unanswered is
why today during the process of intensive dieback of continental coniferous
forests, particularly of the Fir-tree, the typical primary harmful insect-defoliators
such as the fir-moth (Argyresthia fundella F. R.) are missing although they were
present in big gradations at the beginning of the dieback process in the fifties.
Pines in the Adriatic region are exposed to severe attacks of the pine Thaumatopea.
Their gradation is in process at the moment, and in the current period
of big droughts and attacks by the red rot fungi (Fomes pini Fr.) great danger
exists from large scale dieback. Yellowing an dropping of pine deedles is caused
by the leaf-gall fly (Thecodiplosis brachyntera Schweig.)

From the aforementioned it can be concluded that aparat from climatic disorders,
anthropogenic influences — of which environmental changes and especially
emissions, are most, important, defoliation plays a decisive role in thci
process of epidemic dieback and perishing of forests.

Key words : forest dieback, defoliation, anthropogenic influence, physiological
disorders, harmful entomofauna eco-systems, drought, epidemics.