sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ Faculty of Forestry Journal
spread of N. fuckeliana was examined within the tree using isolations. Wound type
was found to be very important for flute canker development, with trees with deep
wounds showing largest stem depressions and most spread of N. fuckeliana within
the tree. Shallow stem wounds also resulted in some stem depressions however
these were usually small and there was only a little vertical movement of the
fungus through the stem. Inoculation of branch stubs resulted in few or small stem
depressions and the fungus was largely contained within the branch trace. Both
inoculation types (ascospores and conidia) resulted in similar levels of stem
depressions and fungal spread within the tree.
3. INFECTION THROUGH BRANCH CROTCHES
Pinus radiata grown in the southern regions of New Zealand is frequently
subjected to snow events during the winter months. Due to the acute branching
angle of P. radiata this often results in severe branch bending and can lead to
branch breakage. This severe branch bending can lead to openings in bark of the
branch crotch which may provide an infection court for fungal spores. Forty eightyear-old
Pinus radiata trees were used to examine this theory. On each tree, six
branches of similar size were selected on the same or adjacent whorls. Each branch
was then subjected to one of two bending treatments (bent with string to simulate
the weight of snow on the branch, or unbent) and one of three inoculum sources
(control, Acremonium conidia on a colonised twig, or a piece of bark containing N.
fuckeliana perithecia with ascospores). The inoculum source was glued or stapled
directly above the branch crotch. Trees were checked after 6 and 12 months for any
canker development and no change to the trees was observed. After 18 months, 20
of the trees were felled and dissected through the branch traces. Isolations were
undertaken to determine whether N. fuckeliana was now present within the stem
tissue. No N. fuckeliana was isolated. The remaining 20 trees will be monitored for
a further 6-12 months and may be felled if any external symptoms of Nectria flute
canker develop.
4. INFECTION THROUGH BRANCH COLLARS
Although inoculations directly into pruned stubs were not always successful at
initiating N. fuckeliana spread throughout the stem (see section 2), the symptoms of
Nectria flute canker are almost exclusively associated with pruned branches.
Incidence of Nectria flute canker in a stand can be much higher than 22% (the
proportion of colonisation recorded in unpruned trees) and so some infection may
be occurring at the time of pruning. If the branch collar was damaged during
pruning, it is possible that this branch collar may act as an infection court for N.
fuckeliana. To investigate this, 41 eight-year-old P. radiata trees were pruned in
the lower third of the stem and three branch collars on each tree were inoculated
with an Acremonium spore suspension. Great care was taken to prevent the spore
suspension spreading onto the rest of the pruned branch surface. The remaining
138