Timber iQ February - March 2019 // Issue: 42 | Page 42

FEATURES
Continued from page 38
has been recently discovered in Sandton, which is Johannesburg’s
economic hub. This discovery is particularly concerning because
Johannesburg is believed to be one of the world’s largest urban forests
with more than 10 million trees. It has been confirmed in Durban,
Hartswater, Bloemfontein, George, Knysna and Johannesburg.
Apparently, the beetle itself doesn’t kill the tree; rather it is the
fungus that accompanies the beetle. FABI unpacks how this happens, ‘It
bores through the bark into the sapwood of the trees and inoculate the
fungus into living wood. The fungus grows in the tunnels of the beetle
and serves as 'vegetable garden' for the beetle larvae, but insusceptible
in trees, the fungus can spread through the sapwood causing disease or
even death of the tree.’
Although, the beetles are too small to detect, an infected tree can tell
all. The symptoms of infected trees vary from one tree species to
another and there are many signs that show when a tree is infected.
Some of the signs include:
• Wilting trees
• Dead branches
• Exit / entry holes on the bark of the trees
• Shotgun-like lesions on the bark at entry / exit holes
• Sugar volcanoes on the bark at entry / exit holes
• Blotches of oozing resin on the bark at entry / exit holes
• Wood frass (wooden powder) on the bark at entry / exit holes
IDENTIFYING THE BEETLE
Since 2017, the beetle has been seen in various
parts of the country.
The PSHB along with
its fungus has caused
tremendous damage to the
trees in the US, specifically
California, in addition to
regions in the Middle East.
The PSHB infects more than 200 tree species from 28 plant families.
However, some of the commercial species that are susceptible to the
shot hole borer beetle include:
• English oak
• Pin oak
• Southern magnolia
• American sweetgum
• Cape beech
To view the full list of species on FABI’s website, visit:
www.fabinet.up.ac.za/pshb.
Industry experts lament that treatment for beetle infestation isn’t
available. Cutting the tree down and burning it is the best solution so
far. Random Harvest, an indigenous plant nursery, recommends that
care be taken when moving wood around in the form of fire wood and
mulch because the beetle can be moved with these, inspection of
nurseries so that infected trees are not sold to distant locations
creating new sources of infection and relooking at sanitation of
infected wood.
However, a wood preserver should be used to facilitate shelf life of
the material. The hazard to which wood material will be subjected has
an enormous bearing on the extent to which wood preservation will be
effective. A piece of wood kept continually dry inside a building is
subject to a much lower hazard than a piece embedded in the ground.
For ground contact hazard, a heavy-duty preservative such as a CCA or
creosote is required with continuous penetration to a significant depth
and with relatively high retentions.
Public appeal has been made by various organisations to report new
cases or find out more information about the beetle.
40 FEBRUARY / MARCH 2019 //
PREVENTING INFESTATION
Environmental experts say the best treatment so far
is to cut down the tree and burn it.
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