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ESTATE NEWS

POLYPHAGOUS SHOT HOLE BORER

AT SILVER LAKES

he Polyphagous Shot Hole Borer
(PSHB) (Euwallacea fornicates) has
Tbeen decimating trees, both soft
and hard woods, across South Africa. In
particular, KZN, George, Knysna and JHB/
PTA areas are severely infected. Of great
concern are the early signs of infestation
in our indigenous forests such as in the
Kruger National Park.

Origin and Characteristics
Polyphagous means “feeding on many
foods” , therefore many indigenous trees
are at risk.

The PSHB beetle originates from Southeast
Asia and was detected in 2017 in Durban
Botanical Gardens, where London Plane
trees were infected. The beetle probably
found its way to South Africa via wooden
pallets on cargo ships.
The PSHB beetle the size of a pencil
tip, 2mm in length, has a symbiotic
relationship with the Fusarium fungus
(Fusarium euwallaceae). Since only the Once the Fusarium fungus spores enter a Infestation has also been observed on
female is able to fly, she carries spores of host tree the fungus grows in the xylem some residence properties. Some forty
the Fusarium fungus with her as she bores of the trunk which is the newest layer of trees are currently being treated.
into trees. The female is able to fly up to wood, just underneath the bark. It is in this
seven kilometres a day. She lays her eggs area that copious amounts of water and Treatment of PSHB
just underneath the bark where they then nutrients are transported to the top of the Since it is the Fusarium fungus that kills
hatch. The breeding cycle of the female tree. Since the fungi require lots of water the tree and PSHB lives off the fungus it is
could be as many as seven times a year the tree is starved and therefore dies. essential to eradicate the fungus and then
producing as many as one billion off- treat the borer. Two methods of treating
spring a year. The males are tree bound Signs of Infestation trees exist.
and randomly tunnel through the wood. The fungi starve the tree of water and
Tunnelling, therefore, starts from the nutrients, so a first and tell-tale sign is One is a seven-week programme whereby
inside and is thus less conspicuous. Both when a tree starts dropping leaves from the tree is first sprayed with an antifungal,
male, female and hatchlings live off the the top. Branches become bare at the eco-friendly, natural product every
Fusarium fungus. top. Important to note that many trees are alternative week. That would be weeks
deciduous and lose their leaves in autumn. one, three and five. In weeks two, four
Only certain trees are host trees, i.e. trees in It is therefore important to look for other and six, a natural, eco-friendly pesticide is
which the female will lay eggs. Host trees signs as well. In indigenous trees it is more sprayed specifically to control the beetle.
can be defined as either Reproductive Host difficult, but when a tree starts oozing sap, The pesticide has been registered under
Trees or Non-Reproductive Host Trees. gum or sometimes sugar bombs it will Act 36 of the law. In week seven a natural
Reproductive Host Trees are trees where darken the bark. That would be a spot for booster is applied to the tree.
the PSHB can successfully reproduce, and investigation. Secondly the borer leaves
which eventually die due to the fungus. wood shavings on the trunk or where two Method two is a process whereby holes
Non-Reproductive Host Trees are attacked branches separate. are drilled into the tree with an active
by the beetle, but PSHB reproduction is ingredient permanently fixed to a tree
not successful. This does not mean that Infestation at Silver Lakes and then applied via a funnel. This is
the fungus is not spread to other trees, be- approximately a six-month long process.
cause the female carries the spores as she Sadly, some trees at Silver Lakes have died Silver Lakes Golf Club has opted for option
attempts to lay eggs in Non-Reproductive due to the infestation. An example can be one due to the eco-friendly application
trees. Reproductive trees found on Silver seen behind the 17th tee box. and shorter time duration to save our trees.
Lakes estate include the following: Acacia Another heavily infested tree is the
xantoephloea (Yellow Fever Tree), Erythrina monkey thorn originally called Acacia Further information may be obtained from
caffra and lysistemon (Coral Trees) and galpinii now called Senegalia galpinii, on Gerhard Olivier at gerhard@phezulu.biz.
Vachelia sieberiana (Paper Bark Thorn).
the 14th fairway on the left just past the
ladies’ tees.

INTRA MUROS MARCH 2020 29