QUESTION: Pittosporum branch dieback--What causes
this?
ANSWER: This sounds like a lower fungal stem
canker and/or a fungal crown rot. This is usually observable as
an obvious blackened to gray discoloration in the lower stem or
crown area. Infection damages the vascular tissue in that critical
area, interfering with the movement of water to the upper portion
of the plant, thereby causing limb and branch die back. If the
entire crown is involved, the entire plant usually declines and
dies. No realistic control other than to keep the plant non stressed
and actively growing. Fungicides have not proven useful. Larry
Barnes, Plant Pathologist, Texas A&M
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