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Title: Crown Symptoms of Regrowth Dieback
Authors: Plazer, C.
Issue Date: Oct-1983
Publisher: University of Hawai'i Press
Citation: Palzer C. 1983. Crown symptoms of regrowth dieback. Pac Sci 37(4): 465-470.
Abstract: Symptoms in the crowns of Eucalyptus obliqua and E. regnans
trees affected by "regrowth dieback" are reevaluated and amplified using tree
climbing, tree felling, and optical study methods. A distinction is made between
the dying upper branches and the lower crown of dieback-affected trees.
Declining branches showed an increase in mortality or absence of growing
shoots, naked buds, and accessory buds with increase in dieback severity.
Mean distance between leaf scars indicated that growth rate of shoots was
slowed before death. With increase in dieback severity of a branch, leaf size
and leaf area index were reduced. Leaves on dieback-affected branches showed
increased chlorosis and reddish colors. There are common features linking
dieback-affected shoots with shoots showing mild "witches brooming."Twiginhabiting
insects are considered of only secondary importance. There was no
evidence of any culturable microorganism from the vascular system. The
symptoms could be the result of water deficits and high leaf temperatures.
Alternatively, the symptoms are suggestive that microbes such as a virus or more
especially a mycoplasma are involved.
URI/DOI: http://hdl.handle.net/10125/748
ISSN: 0030-8870
Appears in Collections:Pacific Science Volume 37, Number 4, 1983



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