sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ ORMAN FAKÜLTESİ DERGİSİ
Canker width was correlated to canker length, which was due to canker shape,
since the majority of cankers were oval shaped. Regression analysis with a linear
model (canker width = 14.6 + 0.44 × canker length) gave correlation coefficient of
0.87. Coefficient 0.44 tells that canker width measured usually about a half of
canker length.
Possible entry points for E. parasitica are branch stubs and bark wounds
(French, 1969). Great majority of cankers were traced to branch stubs as the
avenue of entry. Only 3 out of 89 cankers were associated with bark wounds and
all three wounds resulted from logging operations.
3.3. Area and shape of canker on the trunk
The largest Eutypella canker measured 1.7 m 2 , although the average was much
lower, i.e. 0.5 m 2 (Table 2). The canker area varied a lot because it depended upon
the canker age. The cankered area ranged from 4% to 90% of the trunk area with
the canker, with an average of 48%.
The area without bark also depended upon the canker age and thus the whole
canker area. In order to determine if in fact there was a relationship between the
canker area without bark and whole canker area, regression analysis using a linear
model was carried out. The linear model described a relationship between canker
area without bark and whole canker area. The equation of the model was: area
without bark = –2.32 + 0.25 × whole canker area. The high correlation coefficient
(0.83) showed a good linear relationship between the canker area without bark and
whole canker area. The coefficient of the equation tells that the area without bark
represented usually a quarter of the whole canker area when the canker was old
enough to bark fall off. The bark begins to fall off a trunk due to high degree of
decay or/and high activity of bark beetles.
Perithecia do not usually develop nearer than the fourth or fifth annual callus
ring from the margin of the cankers (Davidson and Lorenz, 1938). Therefore,
Davidson and Lorenz (1938) stated that perithecia are confined to only a small
central portion of large cankers. During this study, their hypothesis about the area
size covered with perithecia was tested. The part of their hypothesis was rejected. It
was confirmed that perithecia are usually located in the central portion of the
canker but this area is not small. The total area of bark covered with perithecia
could exceed 68% of the whole canker area. An average of 32% (±7% at 95%
confidence level) of the canker area was covered with perithecia. Further analysis
was performed and it was found that the correlation between the total area of
perithecia and the area of the whole canker was very good. Simple regression
analysis produced a correlation coefficient of 0.94. A simple regression was made
using a linear model: total area of perithecia = –3.93 + 0.42 × whole canker area.
Three different densities of perithecia were delineated. The high densities of
perithecia were usually located nearer to the canker centre while low densities were
located nearer to canker margin. It should be noted that a middle density of
perithecia could hardly be distinguished from high density. Therefore, some
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