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ŠUMARSKI LIST 9-10/1973 str. 67     <-- 67 -->        PDF

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Summary


Die-back of Eastern White Pine (PINUS STROBUS L) in cultures


The Eastern White Pine along with Spruce, Scots Pine and European Black
P.ne is the most represented species in Croatia´s coniferous cultures. Several years
ago was noticed its group- and stemwise dying away. It is more intensive in pure
stands than in mixed ones. For the purpose of studying this problem three characteristic
localities, viz. Gornje Iz mje, Velika Buna and Dugave, were selected. In
all three localities the intensity of die-back was equal and symptoms the same.
The needles become light yellow, thereafter reddish-brown and do not fall off.
This phenomenon appears most often in circles and usually begins at the lower
more humid part of the slope or microdepression.


In each of the selected localities was laid out one sample plot for the following-
up of the intensity of die-back and performing other investigations. The author´s
initial investigations were directed towards the definition of soil conditions on
experimental plots, to the search for differences in the development of aboveground
and underground parts between the healthy and dead standing trees, to the recording
of appearance and intensity of the attack of diseases and of noxious entomofauna.
The results achieved are presented in this paper.


On the basic of the soil investigations in the localities of Gornje Izimje and
Velika Buna a trench-ploughed slope pseudogley was determined, while in the
locality of Dugava a wery weakly superficially gleyed lessive soil. The intensity
of die-back is influenced by the micro- and mesorelief of terrain which perform
a redistribution of precipitation and lateral waters. The performed analyses of sample
trees demonstrated that there were no significant differences between the
healthy and dead standing specimens in the aboveground part, and no significant
differences in the rooting depth either. On the basic of the average lenght of the
lateral roots the author established that the area of engaged soil in healthy specimens
in relation to that of the dead standing ones is by 20°/o larger. The ratio
of the area of angaged soil to crown projection in healthy specimens is 2,59:1, and
in the dead standing ones 1,75:1. The fungal diseases honey fungus (Armillaria
mellea Vahl.), needle-cast fungi (Hypcdermia desmasierii Duby), Verticicladiella spp.
and the noxious entomofauna White P.ne bark aphid (Pineus strobi Htg.), Pine
weevils (Hylobius abietis L., Pissodes pini L.), bark beetles (Pityogenes bidentatus
Herbst., P. bistridentatus Eich., P. calcographus L., P. quadridens Hart.), Pine cone
moth (Dioryctria splendidella H. S.), fox-coloured Pine sawfly (Neodiprion sertifer
Geoffr.), which were recorded in selected localities, may be of primary or secondary
significante, and in unfavourable site conditions they may be the cause of
Eastern White Pine die-back. There exist also the first indications according to
which the causative organism might be the determined fungal disease produced
by Verticicladiella opp.


These investigations are being continued.