How to identify PSHB on tree trunks: Round 1mm wide entry-holes to beetle tunnels. Look for dark, wet staining; thick gumming; streaks of white powder or fine sawdust coming from holes. Symptoms are unique to each tree species. (Photo: ZW de Beer, fabinet.up.ac. za; information: www. capetowninvasives. org.za)
THE Western Cape Disaster Management Centre (WCDMC) has been monitoring the spread and the risk posed by a notorious tree killing beetle known as the Polyphagous Shot-hole Borer (PSHB), since August 2018.
To date 100 infected trees have already been removed in the Western Cape.
Trees in amongst others Somerset West as well as two South Cape towns, George and Knysna, have been infected.
The Minister of Local Government, Environmental Affairs and Development Planning, Anton Bredell, says the beetle is an alien pest that targets healthy trees and kills them.
“The beetle infects the healthy trees with a disease that rapidly kills them.
“It has been known to infect over 110 different tree species including fruit trees like grapevines and avocado trees.”
Bredell says if the beetle threat is not controlled, it could have a serious and disastrous effect on the agricultural and tourism sectors in the province. Notable areas of devastating current infestations include suburbs of Johannesburg such as Sandton and Houghton.
The beetle is tiny, smaller than 2 mm, it reproduces rapidly and has no natural enemies in Africa. It appears to be spreading rapidly.
The first outbreaks were reported in 2017.
“The National Department of Environmental Affairs, Forestry and Fisheries should immediately take full responsibility to control and eradicate to spread of PSHB,” says Bredell.
Bredell has also urged municipal councils not to take the matter lightly.
“The city of Cape Town has established a task group and is addressing the problem and has established a 24-hour reporting portal.
“They have indicated that this portal may be able to accommodate other municipalities too. I’m urging municipalities to grasp this offer and work together to tackle this scourge.”
In addition, the National Disaster Management Centre (NDMC) has been briefed by the province and has indicated it will escalate the matter at a national level.
• For more information on the beetle visit https://www.fabinet.up.ac.za/index.php/pshb and https://www.capetowninvasives.org.za/shot-hole-borer
The most visible impact of the PSHB invasion in South Africa is in urban forests on street, park and garden trees, and this became the focus of many articles in the media. Many trees have been killed by PSHB in Sandton, George, and Knysna, while reports from Sedgefield, Bloemfontein, Ekhurhuleni, Jankempdorp, Hartbeesfontein, Pietermaritzburg and Durban suggest that the impact is becoming worse in those areas. The most common trees to be killed are English oak, Chinese maple, Japanese maple, boxelder, and sweetgum.
Of great concern is the recent discovery of PSHB on London plane and sweetgum in Somerset West in the Cape Peninsula. With the major impact of the disease on oak trees in especially the George and Knysna areas, it is inevitable that the famous oaks of Stellenbosch and the surrounding wine farms will be dramatically impacted.
Most unpredictable is the impact that the PSHB invasion will have on our native forests. Several native tree species were found to be infested in the gardens of Sandton, George and Knysna, with species like the coral tree, keurboom and Cape willow being particularly vulnerable and often killed. It is now known that the beetle is spreading from the urban areas into native forests close to the towns of George, Knysna and Durban. However, which species will be affected and to what extent, is unpredictable. (https://www.fabinet.up.ac.za/index.php/pshb)