sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ ORMAN FAKÜLTESİ DERGİSİ
world mostly in temperate zones. Bangladesh has reported some of the largest
hailstones ever measured and more hail-related human deaths than anywhere else
in the world. In Canada, the foothills area of the Rocky Mountains, especially in
the province of Alberta, is known to have more incidences of hail storms. Hail
damage can be localized in small areas but areas as big as 10-km wide are also
recorded.
2. OBSERVATIONS
In the fall of 2008, at Mount Assineboine Provincial Park, in British Columbia,
Canada, I observed wide areas of natural forests of mature subalpine fir (Abies
laciocarpa (Hook.)Nutt.) that were severely discoloured with many dead branches.
No fungal or other biotic signs were present. After close examination of the
damaged branches and topographical features of the area, I concluded that the
symptoms were most likely caused by hail that occurred early in the summer, a few
months before my visit. Symptoms included half- healed wounds on the upper side
of the branches and many fallen branches on the ground. Needles positioned
beyond the wounds on branches were often discoloured. Also, the damaged stands
were facing a lake and the damage occurred mostly on the exposed side of the
stand, indicating that the hail storm hit sideways from the direction of the lake.
3. DISCUSSION AND CONCLUSION
Hail damage as well as other harmful non-biotic conditions, such as severe
drought and frost damage, will serve as predisposition factors to fungal and
bacterial shoot and stem diseases. Trees in the affected areas need to be carefully
examined and diagnosed. These climatic and physiological damages to trees
initially do not have signs of fungi or bacteria, but they are often invaded by certain
fungi or bacteria later, and they are often misdiagnosed as caused by secondary
fungal invaders. Genera of fungi such as Cytospora, Nectria, and Sphaeropsis are
known to be in this category of fungi on stems and branches of forest trees
(Blodget et al., 1997; Zwolinski et al., 1995). In our recent publication of forest
tree diseases of west-central Canada (Hiratsuka et al., 2004; Hiratsuka, 1987) we
used expressions such as “Nectria and Cytospora associated with canker of broad
leaf trees—” rather than “Nectria canker” or “Cyotspora canker”. So called
“Screloderris canker” caused by Gremmeniella abiteina is also likely triggered by
one or more non-biotic predisposition factor.
It is important to consider non-biotic factors, including hail damage, as
important predisposing conditions when we diagnose forest tree health problems,
especially in cold climatic regions such as those in Canada.
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