Weekend Argus (Saturday Edition)
Targeting the invaders
Local authorities are urging residents to look out for shot hole borers in trees and to report possible sightings, via an online reporting tool
THE POLYPHAGOUS shot hole
borer or PSHB (Euwallacea
fornicates), a tiny Asian beetle
about the size of a sesame seed, has invaded, damaged and killed thousands of trees across the country.
Capetonians are urged to be on the lookout for PSHB and
Fusarium dieback following unconfirmed reports of the beetle on the Peninsula.
The City’s Recreation and Parks Department and the Invasive Species Unit have operational plans in place to deal with PSHB should Cape Town’s trees show symptoms of infestation.
Councillor Zahid Badroodien, the mayoral committee member for community services and health, said the damage caused by the beetle should not be underestimated.
“An invasive species of this nature could go undetected as people don’t usually inspect trees to see if there are beetles,” said Badroodien.
“That is why it’s important the
City informs residents so they can report sightings.”
BEETLES INVADE TREES
Adult female beetles burrow into trees to establish brood galleries and lay eggs. The female introduces its fungal symbiont, Fusarium euwallaceae, into galleries as food for developing larvae and adults. The fungus disrupts the flow of water and nutrients to the tree, causing
Fusarium dieback which leads to branch dieback and possibly tree death.
PSHB has been reported in cities and towns around the country, including Joburg, George, Knysna, Richards Bay, Bloemfontein, Durban and Pietermaritzburg, where the beetle was first discovered in
2017 by Forestry and Agricultural Biotechnology Institute (FABI) researcher, Dr Trudy Paap.
TREES AFFECTED
In both Israel and California, where it was first identified in 2003, the beetle has caused extensive and costly damage to urban and agricultural trees.
PSHB attack a number of different trees, both exotic and indigenous species, but only reproduces in reproductive host trees.
In non-reproductive hosts, the fungus may or may not cause disease and kill the tree.
SAFE DISPOSAL
When heavily infested trees are felled, the wood needs to be disposed of correctly and responsibly.
Beetles can live for months in cut wood and researchers believe incorrect disposal is fuelling the spread of the beetle to other areas.
Infected wood should be burned or wood chipped. The wood chipping progress builds up heat with kills the beetles and the fungus.
Solarisation, where wood chips and logs are placed in the sun and covered with black plastic for six to eight weeks, has also proved to be effective.
If infected wood needs to be moved, it must be wrapped in plastic and sealed before transport.
The City of Cape Town has a safe disposal plan in place.
Infected wood will be chipped and held at the closest landfill site for solarisation.
WHAT CAN BE DONE?
“Where trees have been lost we do see a changing landscape and this will be in the case in the Cape over the next five years,” said Professor Wilhelm de Beer of FABI. “While it is important to be concerned about our trees, we should also note that not all trees will die.”
So what can Cape gardeners do?
Improve tree health
Healthy trees may be able to fight off an attack. Ensure your trees have the right nutrients and water requirements. Add compost to the soil around the tree and add a layer of mulch.
De Beer says it is best to treat the tree as it grows in nature. Overwatering can also cause stress, as can wind or extensive heat reflected from paving and walls.
Be vigilant
Treatment can be effective if infestation is detected early, especially on a minor branch.
REPORT SIGHTINGS
1 Log on to www.invasivescapetown. org.za/shot-hole-borer (short url: goo.gl/HcLzhD or use the supplied QR code) and click on the green report button at the bottom of the page.
2 The tool will take you through a series of steps where you will be asked to provide details on the sighting (beetles, holes, branch dieback or dying trees) as well as your name and contact details and a GPS location for the sighting. Photographs can also be uploaded.
3 You can also send photographs and wood samples to FABI for identification. Details of this procedure can also be found on the shot hole borer Reporting Tool website.