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dieback disease in susceptible
host trees. High levels of
infestation of susceptible host
trees have resulted in high
levels of tree deaths.
So far, no insecticides have
been found to work, as the
beetles bore too deeply into
the trees.
The beetles are quite
indiscriminate and attack
both indigenous and non-
native trees.
In other countries crop trees
like avocado, grapevine,
peach, orange and some nut
trees have been attacked.
Signs and symptoms of PSHB
attack can vary, a lot depend-
ing on the type of tree,
however, tiny beetle entry
and exit holes (a bit smaller
than the tip of a ballpoint
pen) are usually present in
the tree's bark. Sawdust is
often found around the holes
or on the ground around the
trunk; sometimes a sawdust
“toothpick” can be seen
sticking out of the beetle
hole. In areas around the
beetle holes, trees may show
signs of liquid or resin oozing
out of the bark or 'sugar
volcano' symptoms - little
cone-shaped piles of white
powdery stuff on the bark.
Many adult female polyphagous shot hole borers, shown by red arrows,
can be seen in this cross section of an infested tree. Their winding
galleries can reach to a depth of around 8 cm into the tree's wood.
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www.sasmallholder.co.za
NEWS
A working group of entomol-
ogists, scientists and govern-
ment officials has been set up
and there is an appeal to the
public to be on the look-out
for the beetles. Details,
including photographs of the
symptoms, GPS coordinates
or a street address, the host
tree species and the reporter's
contact details can be sent to
[email protected]
a.