Trees in South Africa are under attack. Why it’s proving hard to manage

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Trees in South Africa are under attack. Why it’s proving hard to manage

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February 4, 2020 12.35pm SAST |Trudy Paap, Postdoctoral Fellow Forestry and Agricultural Biotechnology Institute, University of Pretoria

More than two years have passed since the detection of what is arguably the most damaging tree pest ever to arrive in South Africa: the polyphagous shot hole borer (Euwallacea fornicatus). The beetle kills trees and there are no proven remedies.

The beetle is now present in nearly all parts of the country and in more than 100 tree species.

An invasion of this magnitude should have elicited a rapid response and the development of a strategic action plan. But that hasn’t happened. South Africa has never had to deal with a tree-killing pest of this importance before. In addition, the country has limited resources and there has been confusion about which government department should take responsibility. As a result, there hasn’t been a coordinated response to deal with the pest.

The tiny polyphagous shot hole borer beetle is 2mm in length and native to Southeast Asia. It has a symbiotic relationship with three species of fungi, including Fusarium euwallaceae. The fungus is a food source for the beetle and its larvae, but can kill susceptible host trees.

The list of host trees in South Africa continues to grow. Not all of these support the whole life cycle of the polyphagous shot hole borer. But it’s been found to breed in 25 species (both exotic and indigenous trees).

The greatest impact has been in urban environments such as Johannesburg. It has been detected on backyard avocado and roadside weedy acacias, but not yet in commercial orchards or plantations. The only commercial crop it’s been detected on is pecan trees.

In California and Israel, polyphagous shot hole borer went on to damage the avocado industry as well as trees in natural ecosystems. There are concerns that this could happen in South Africa too.

But it hasn’t yet been declared an agricultural emergency plant pest and no formal response has been triggered. Based on the Israeli and Californian experiences, it could clearly still pose a threat to economically important crops in South Africa.

The proactive thing to do would be to list the beetle as an emergency plant pest.

Gaps in the system

South Africa is good at managing pests in agricultural settings. This falls under the Department of Agriculture, Land Reform and Rural Development, specifically Plant Health Early Warning Systems. Where a pest is deemed an emergency plant pest, the South African Emergency Plant Pest Response Plan provides for a rapid response to prevent the establishment, spread and coordination of communication between government agencies, academia and plant industry professionals.

For example, detection of the Fall Army Worm (Spodoptera frugiperda), a quarantine pest of maize and sorghum, triggered a rapid and coordinated response overseen by the national government. Provincial departments, academic institutes and industry stakeholders have been working together on aspects ranging from monitoring, training and diagnostics to pesticide registration, legislation and enforcement.

The Department of Environment, Forests and Fisheries provides for listing of invasive alien species that threaten biodiversity, through the National Environmental Management: Biodiversity Act.

The pest risk analysis for polyphagous shot hole borer (the process by which listing is facilitated) has been submitted, but the listing is yet to be finalised.

The country’s laws also place a “duty of care” on all land owners (private and public) to control invasive species on their land. They also require all levels of government – from municipal through to national – to develop monitoring, control and eradication plans for land under their control.

But systems designed for the agricultural or natural environment sector aren’t helping the management of a beetle that’s wreaking havoc on trees in towns and cities.

This is also clear in how the country manages invasive species. It does this well when it comes to weeds and larger animals. But forest pests are barely represented.

Another major challenge is that the borer beetle is particularly hard to manage because of its mating system, wide range of hosts and ability to survive in felled wood for many months. On top of this, heavily infested reproductive hosts become “reservoirs” of beetles, threatening the health of adjacent trees.

Current best practice recommends removal of heavily infested trees in which beetles are breeding. Infested wood should be disposed of appropriately at designated dumping sites to reduce the risk of spread.

But in the absence of a national strategy to guide municipalities, responses to the pest have varied. Cape Town has perhaps led the way with a coordinated city response to the recent invasion in Somerset West. In conjunction with its Invasive Species Unit, the city has developed a management protocol. As one of the more recent areas to be invaded, it’s perhaps had the benefit of being able to better prepare for the arrival of this pest and learn from the experiences of other municipalities.

Research from California suggests chemical control may have an application in protecting individual high value trees. But this shouldn’t be seen as a silver bullet.

In South Africa’s case, various research efforts are underway to shed more light on the beetle and its impact. For example, a unit at the University of Pretoria, the Forestry and Agricultural Biotechnology Institute has been involved in surveillance and monitoring of the pest.

The multi-disciplinary and multi-institutional Polyphagous Shot Hole Borer Research Network has recently been established. With members from ten different academic institutes, the network aims to align and coordinate research efforts by researchers from institutions across the country.

Now with funding made available by the Department of Environment, Forests and Fisheries, further research can be conducted under the framework of this network, to underpin science and data-based management advice.

But a great deal still remains to be done. South Africa would do well to reflect on how it’s responded so far.


https://theconversation.com/trees-in-so ... o%20manage


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Re: Trees in South Africa are under attack. Why it’s proving hard to manage

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0*\

Government will do something once they attack the money tree... O**


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Re: Trees in South Africa are under attack. Why it’s proving hard to manage

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The point is, that they don't care a damn about the future of the country 0=


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Re: Trees in South Africa are under attack. Why it’s proving hard to manage

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Three years on, the shot-hole borer continues to eat away at SA’s trees

By Tony Carnie• 5 December 2020

Image
Student researchers inspect a shot-hole borer beetle infested tree. Photo: FABI

Departmental confusion and delays mean there is no co-ordinated government response.

Tree and insect experts have lamented the government’s slow response to the spread of a tiny tree-killing insect that they believe is “arguably the most damaging tree pest to ever arrive in South Africa”.

In the latest issue of the SA Journal of Science, four senior scientists from the universities of Pretoria and Stellenbosch say that an invasion of this magnitude should have triggered a rapid and coordinated national response.


Instead, three years since its discovery in Pietermaritzburg, the beetle has now attacked more than 100 different tree species, spread to every province except Limpopo, and posed a threat to a growing number of indigenous trees and forests.

The polyphagous shot-hole borer (PSHB) beetle, thought to have arrived in untreated wood products from Southeast Asia, burrows deeply into living wood tissues, eventually killing susceptible trees. Branches die back and some tree trunks look like they have been blasted by a 12-bore shotgun.

To complicate matters, the tiny beetles (each about 2mm long) have cryptic habits and are notoriously difficult to control using chemical pesticides. They spend little time on the tree surface and only swallow small amounts of wood, limiting their contact with pesticides.

The four researchers – Dr Trudy Paap, Professor Wilhelm de Beer and Professor Michael Wingfield from the University of Pretoria, and Dr Francois Roets from Stellenbosch University – have also drawn parallels between the new beetle invasion and the Covid-19 pandemic, noting that both are largely a result of human activities and rapid trade networks.

The global movement of living plants and plant products (including untreated wood pallets, packing material and crating) has created a major pathway for tree pests.

“There is strong evidence linking the role of [human)] disturbance as a major driver of emerging infectious diseases of both humans and forests. Moreover, the unprecedented level of global connectedness via trade and travel networks facilitates the rapid spread of pathogens responsible for human and tree disease pandemics more than ever before,” the researchers say.

There are also strong economic reasons for investing in strategies to reduce the threat posed by future pandemics to both human and forest health.

Image
The polyphagous shot-hole borer beetle. Photo: S. Bush, FABI

To illustrate the potentially serious impacts of invasive tree pests, they note that another invasive beetle pest in the United States, the emerald ash borer, has killed hundreds of millions of native ash trees and cost $10-billion in control measures over the past decade.

Turning to the South African government’s response, Paap and her colleagues said three years had passed since beetle damage was first detected in London plane trees at the KwaZulu-Natal National Botanic Gardens.

“An invasion of this magnitude should have elicited a rapid response and the development of a strategic action plan. However, South Africa has never before had to deal with a tree-killing pest of this importance. Moreover, with limited resources available and confusion regarding which government department should take responsibility, a coordinated response has failed to emerge.”

They note that the management of agricultural pests falls under the national Department of Agriculture, Land Reform and Rural Development whereas the control of alien species that threaten biodiversity falls under the Department of Environment, Forestry and Fisheries.

“The PSHB presents a unique challenge in that it crosses boundaries between agriculture, commercial forestry, natural forests and urban trees…. The PSHB has not yet been declared an agricultural emergency plant pest and no formal response has been triggered.”

Image
Typical shot-hole borer damage to a London plane tree. Photo: FABI

There were similar challenges to listing it as an invasive pest under environmental protection laws.

“Despite submission [in November 2018] of a detailed pest risk analysis, the process by which listing is facilitated, its addition to the National Environmental Management Biodiversity Act list is yet to be finalised.”

There were also problems at the municipal government level: the major impact of the beetle was in urban environments, raising questions of where the responsibility for management of urban forests lies.

In the absence of a national strategy and with no clear structure in place to guide their response, most municipalities had understandably struggled to manage this threat to urban forests adequately.

“We would do well to seriously reflect on the shortcomings of how we as a country have responded to the arrival of the PSHB and learn from them. Importantly, South Africa needs to be able to deal with new invasions more effectively in the future,” say the researchers.

They note that plants and “pests” have co-evolved over millions of years and that damaging outbreaks of native pests in their natural environments are rare. Instead, pests play a vital role in shaping natural ecosystems.

Yet when people moved them to different continents, the new alien pests could find native hosts that lacked “co-evolved resistance”, with potentially devastating consequences. In some cases, these pests have changed ecosystems fundamentally, with entire tree species being almost eliminated from invaded landscapes.

“There are already indications that indigenous tree species at the fringes of infested urbanised areas are susceptible to PSHB infestation,” says Paap.

The researchers reiterated their call for a consolidated national management strategy and an action plan on PSHB, as well as a coordinated public awareness campaign to inform local government, residents and stakeholder groups about the beetle and its effects.

“Municipalities should be encouraged and supported to remove and destroy heavily infested reproductive host trees. Staff from affected sectors (including private, municipal, provincial and national parks and gardens, and landscaping, nursery, tree felling, farming and forestry industries) need to be trained to identify and appropriately handle PSHB-infested material.”

In response to queries, the two national departments (agriculture and the environment) said they were “finalising measures for promulgation to effectively control and manage the occurrence and infestation”.

The agriculture department said because the problem was a cross-cutting issue involving two departments, a steering committee had been formed comprising the departments of agriculture and environment, provincial departments, municipalities, the environmental and forestry sectors, researchers, academic institutions and agricultural fruit and ornamental sectors.

The agriculture department had published proposed regulations for the control of PSHB for public comment on controls in the agricultural sector, compulsory reporting of beetle infestation and quarantining of infested areas, and the environment department had published separate proposals to cover the forestry and environment sector.

Environment Minister Barbara Creecy also published a notice in the Government Gazette in September, calling for public comment on her draft proposal to declare emergency intervention measures that would require landowners or occupiers to report the presence of the beetle to her department immediately.

The proposed measures would also ban the sale of PSHB-infested wood and prohibit certain species of wood (including firewood) from being moved into national parks and other protected areas.

The department recognised that PSHB infestations had devastating environmental and economic effects, so swift action was required. It would provide guidance and advocacy materials to the public in due course. There would also be forums and workshops to educate the public and affected stakeholders on the dangers posed by PSHB. DM168


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Alien invaders

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Alien invaders: The hidden threat to South Africa’s food, water and wild places

By Tony Carnie• 31 May 2021

Image
From left: The polyphagous shot-hole borer beetle (Photo: S Bush / FABI) | The polyphagous shot-hole borer beetle. (Photo: S Bush / FABI) | The fall armyworm. (Photo: SANBI)

South Africa spends more than R1bn every year to fight an army of alien invader species — but a never-ending task lies ahead to limit the relentless spread of a wide range of foreign organisms that are degrading the country’s water resources, farming lands and rich biological heritage.

Some of the stowaways arrive on our shores by clinging desperately to the submerged bottoms of ships and leisure yachts from the Caribbean or the Mediterranean. Others hitch a ride in the bellies of massive cargo ships, in passenger aircraft holds, trucks or trains.

Many more are also welcomed with open arms due to their bright colours, strange shapes and other novel characteristics.

But because most enter the country without passports or paperwork — or are simply too small to be spotted by the human eye — it is impossible to count just how many invaders arrive in South Africa each year.

Image
The hulls of pleasure yachts, encrusted by a variety of foreign and local marine organisms, are just one of many routes through which alien invader species can sneak into South Africa. (Photo: Tammy Robbinson)

Nevertheless, a new assessment by local scientists has formally classified nearly 2,000 alien species that have established a pretty firm beachhead on our shores and are spreading out to take advantage of a vast hinterland where they have no natural enemies to limit their invasion.

The most noticeable alien invader has been SARS-CoV-2, the tiny virus behind the Covid-19 pandemic that has killed well above 55,000 South Africans over the past year.

But there are many other, less visible and less vilified invaders… tiny beetles, fungi or crop-munching armyworms. Songbirds like the Indian mynah; commercial pine and wattle trees or brightly-coloured lizards imported by pet traders or cold-water foreign fish species like trout that have been described as “chainsaws with fins”.

One notable invader is the polyphagous shot-hole borer (PSHB) beetle (and its symbiotic fungus) from Southeast Asia that is chewing its way northwards after being discovered in Pietermaritzburg in 2017. Since then, it has spread to reach every province except Limpopo and has killed thousands of trees, including several historic specimens around George and Stellenbosch.

Launching the latest science assessment on South Africa’s biological invasions on Friday, national environment minister Barbara Creecy said PSHB looked set to become one of the most damaging and costly biological invasions faced by the country.

Creecy said biological invasions were now the third largest threat to South Africa’s biodiversity after cultivation and land degradation, and thought to be responsible for 25% of all biodiversity loss.

Present estimates showed that if biological invasions on grazing land were not controlled, the country could lose up to 70% of this valuable natural asset.

The latest report from the SA National Biodiversity Institute (SANBI) provides a comprehensive assessment of the status of the invaders and is the only country-level assessment worldwide that focuses specifically on biological invasions.

South Africa occupies only 2% of the world’s land surface area and yet is home to 10% of the world’s plant species and 7% of the reptile, bird and mammal species — many of which are being displaced or threatened by invasive alien species.

Image
This historic oak tree, planted in the town of George in 1884, is one of the casualties of the alien polyphagous shot-hole borer beetle. (Photo: Eugene Gunning, George Herald)

Noting that South Africa already spends more than R1-billion annually to control such invasions, Creecy announced that her department had recently secured a significant injection of funding from the Global Environment Facility.

The funding is made up of about R46-million in grant funding and a further R303-million of in-kind support to strengthen the management of invasive alien species.

Some will be used to tackle eight prioritised invader species and to implement new surveillance and detection measures at border posts. Some will also be used to eradicate the alien house mice that kill the chicks of rare seabird species on Marion Island in the Southern Ocean.

There are more than 70 official ports of entry through which people, goods and transport vessels can enter the country. Eight are maritime ports, 10 are airports and 54 are land border posts.

Currently, however, proper biosecurity control measures are only in place at OR Tambo International Airport, while the remaining ports have very limited or sporadic biosecurity capacity.

The latest scientific assessment finds that there are now at least 1,880 alien species that have established themselves in South Africa, about a third of which have been classified as invasive.

Examples include crop pests such as the tomato leaf miner which was detected in 2016, and the fall armyworm in 2017.

The fall armyworm from North and South America feeds on the leaves and stems of more than 80 plant species, causing major damage to maize, rice, sorghum and sugarcane, but also other vegetable crops and cotton.

It is called an “armyworm” for good reason. In its larval stage, it gathers in huge masses which can destroy large areas of crops overnight, while moths from this species can fly up to 100km a night.

Dr Tsungai Zengeya, lead editor of the SANBI report, said estimates suggest the ecological costs of invasive alien plants and animals to be more than R6.5-billion a year.

The main costs are associated with a decline in ecosystem services such as water and grazing, and in agriculture.

The scientists estimate that invasive trees use up to 3%-5% of South Africa’s surface water runoff each year, a serious problem in an already water-scarce country that is increasingly prone to drought.

While this figure might not seem high, SANBI said scientists calculated that Day Zero in Cape Town was brought forward by 60 days due to invasive trees sucking up water in the region. There are similar impacts in other drought-stricken areas, such as the Eastern Cape.

The report also highlights another significant threat from invasive trees. Because they provide extra wood fuel, they increase the risk and intensity of veld fires such as those that swept through Knysna recently.

SANBI researcher Dr Katelyn Faulkner noted that at least three new invader taxa slip into the country each year, including foreign marine organisms which enter South African waters via ballast water that originated from thousands of kilometres away.

Some organisms also attach themselves to the hulls of ships and leisure craft and recent research in local waters has highlighted the role of recreational yachts, particularly those used for cruising, in the dispersal of marine alien taxa within South Africa.

More than 100 alien plant species have entered South African national parks and game reserves. Most were intentionally introduced to the country as ornamental plants or were dispersed by rivers and animals.

Examples include a freshwater snail (Tarebia granifera) from Southeast Asia, that is dispersing rapidly within the country via aquatic plants and birds or as a stowaway on boats and trailers.

The report emphasises the need for adequate funding and management to tackle alien plant invasions on a consistent and determined basis.

One example comes from a major setback in weed control in the 90,000ha Hluhluwe-iMfolozi Park in KwaZulu-Natal. The alien triffid weed (Chromolaena odorata) was first noticed in the reserve in 1978 and then spread rampantly, to cover more than half of the park by 2003.

After a substantial investment in weed control (R103-million in funding and 2,000 person-years of effort), the invasions were reduced to acceptably low levels by 2011.

However, the success of this operation was now in question as most of the gains had now been reversed “due to a number of complicating factors”, the report notes.

One of the reasons was the tragic death of a field worker who was killed by an elephant. This led to a directive from the Department of Labour that teams would not be allowed to work in the field unless accompanied by an armed guard.

However, due to funding cutbacks in the provincial Ezemvelo KZN Wildlife agency, extra armed guards were not available and it was not possible within the rules of the Extended Public Works Programmes to train and adequately remunerate new armed guards. Because the implementing agency also failed to spend money allocated to the project, funding was withdrawn in line with Treasury rules.

Although alternative sources of funding were subsequently found, this led to a two-year halt in weed control in the reserve — during which Chromolaena reinvaded most of the cleared sites.

“Overall, therefore, the (initial) gains appear to have been reversed, and additional funding, which is unlikely to materialise under current economic conditions, would be needed to bring the situation back under control. This experience illustrates the complexity of alien species control operations, the need for more flexible approaches to be able to deal with them, and the fact that invasions can rebound quickly if maintenance management is not consistently and continuously implemented.”

Creecy has also emphasised the need for a more coordinated approach to tackling the complex problem.

Recognising that this was a multifaceted problem that needed a multifaceted approach, Creecy said there was a need to cut through red tape and the silos of different government departments to arrive at a common national approach.

Accordingly, her department was developing a new policy on the management of biological invasions, supported by a 10-year National Invasive Species Strategy and Action Plan.

The aim of the strategy was to facilitate a more cohesive and collaborative approach by government, industry and the broader community to identify and manage biosecurity risks. The new strategy would be published for public comment and input shortly. DM


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Re: Alien invaders

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Never-ending struggle indeed! 0:


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Re: Alien invaders

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If only we had started the struggle before......


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Re: Trees in South Africa are under attack. Why it’s proving hard to manage

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From leachy, in Punda Maria, I think?

20210602_115639.jpg
20210602_115719.jpg


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Re: Trees in South Africa are under attack. Why it’s proving hard to manage

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Boring to death: Meet the rampant beetle posing a huge threat to historic Cape trees

Image
The polyphagous shot hole borer beetle. (Photo: S Bush, FABI)

By Rebecca Pitt | 10 Feb 2022

The shot hole borer beetle has become a threat for historically important trees in the Western Cape. The beetle is 7km away from Stellenbosch’s tree-lined streets. Once it arrives there, it will be ‘too late’.
____________________________________________________________________________________________________________________________
Since 2019, more than 1,000 trees in Somerset West in the Western Cape have been cut down due to dieback caused by a tiny beetle that bores into tree trunks. It leaves behind a fungus that threatens to kill.

The beetle, known as the polyphagous shot hole borer (PSHB) beetle, is small, being only 1.5mm to 1.7mm long – about the size of an ant. But its activity on susceptible tree varieties has calamitous consequences, taking down ramrod-strong and old oak trees.

Somerset West is a hotspot area in the City of Cape Town where these invasive beetles have spread in the Western Cape, according to Professor Francois Roets, head of the Department of Conservation Ecology and Entomology at Stellenbosch University.

“There are at least 5,000 trees infested,” he said.

Roets, who is currently conducting research on the beetle, said that part of the reason Somerset West is heavily infested is because of slow reaction in detecting the beetle.

Image
Chemical injections on an Oak tree at Vergelegen. (Photo: Supplied by Vergelegen)

“The whole of Somerset West are not playing their part,” said Roets, adding that residents don’t want to cut down their trees because initially the infected trees look fine.

Cape Town’s deputy mayor and mayoral committee member for spatial planning and environment, alderman Eddie Andrews, said the City’s current strategy and aim is to contain the infestation to the Somerset West area.

“According to our most recent records, the beetle has not been found elsewhere in Cape Town,” Andrews said.

The City is felling, chipping and incinerating highly infested and reproductive host trees.

While the beetle hasn’t yet arrived in Somerset West’s neighbouring town, Stellenbosch – which is renowned for its historically important trees, especially its oaks – it’s on its way there, only 7km away, Roets said.

Stuart Grobbelaar, spokesperson for Stellenbosch Municipality, said the municipality has plans to preserve its trees.

“Once an infected tree is identified and experts have analysed the situation, the tree will be treated or removed and disposed of safely.

Image
Vergelegen risk and commercial manager Leslie Naidoo and researcher Heather Nependa at a giant camphor tree, fitted with repellent pouches. (Photo: Supplied by Vergelegen)

“The municipality continuously plants new trees where older or sick trees are removed,” said Grobbelaar.

“Residents are encouraged to inform the municipality when they spot holes the size of a toothpick on the trunk or branches of trees. These holes can be with, or without, the white wood powder and are usually found in the cracks of thick bark.”

But according to Roets, the beetles should be monitored using traps before they invade the town’s trees, of which many are highly susceptible to the beetles’ fungi. “Once found in Stellenbosch, people will find it is too late.”

Across provincial borders

The beetle invader, which originates from South East Asia, is moving all over the country. The Forestry and Agricultural Biotechnology Institute (FABI) team from the University of Pretoria first detected the PSHB in South Africa during routine tree health monitoring at the KwaZulu-Natal National Botanical Garden in Pietermaritzburg.

“The first evidence of the beetle in South Africa is from a DNA barcode of insects collected in Richards Bay in 2012,” said Roets.

The City of Cape Town seems to be the only municipality proactively working from the start to mitigate the beetle’s spread, said Roets.

“Other municipalities across the country have been slow to react,” he said. “Now the focus is on removing heavily infested trees to reduce the impact and possibility of further spread, but it is likely that it will travel to numerous new destinations in the coming years.

“Little is being done in Johannesburg, Durban, Makhanda, George. In Johannesburg, it has taken them four to five years to do anything.”

According to a November 2021 paper, The Polyphagous Shot Hole Borer (PSHB) beetle: current status of a perfect invader in South Africa, there is great risk of accidental introductions of the beetle owing to limited inspections – “a consequence of a lack of trained personnel and funding”.

The tiny beetles are easily missed, hitchhiking on goods and material such as nursery stock, and they contaminate wooden products, the paper states.

According to Roets, the beetle – which feasts on English oaks, Acer species, willow trees, box elders and plane trees – is able to spread at a rate of about 4km per year on its own.

“Oak trees may die within three years of first infestation… Some box elder trees have died much quicker than this… Plane trees take a long time to succumb, more than five years,” he said.

Image
Professor Francois Roets from Stellenbosch University is researching the invasive species. (Photo: Rebecca Pitt)

First indications of infestation are unassuming, with some trees showing tiny holes on the bark. Other signs include stain marks on the bark, the oozing of tree gum or frass (a powdery refuse) on the trunk or branches, and sudden branch dieback.

While the initial signs can go unnoticed, “in one or two years’ time the problem explodes and you need to cut down dying trees”, Roets said. So far, there is damage worth about R10-million – R3-million from monitoring and tree removal, and an estimated R7-million being spent on the replacement of trees, he said.

Over the next 10 years, hundreds of thousands of trees would be lost, Roets predicted.

A neighbourhood infestation

The beetle “was most likely transported to Somerset West in leftover firewood from the George/Knysna area in 2019 and has been spreading in this area since then,” Roets said. “It is starting to move into more natural areas as well, [like] the Helderberg Nature Reserve – the Keurboom especially.”

On Vergelegen Wine Estate in Somerset West, the beetle presently infects 14 trees. Of these, one English oak, two box elders, two trident maples and one Japanese maple have been treated, said Leslie Naidoo, Vergelegen risk and commercial manager.

Some neighbouring farms in the area are in a worse situation.

Image
Many of the trees that line Stellenbosch streets are susceptible to the invasive beetle, including oaks and willows, according to Professor Francois Roets from Stellenbosch University. (Photo: Rebecca Pitt)

At Lourensford in Somerset West, more than 100 trees are affected and so far 30 have been cut down after showing signs of dieback, said Koos Jordaan, general manager at the estate.

“Fortunately we have not yet had any infections in our fruit trees, nor indigenous trees,” Jordaan said.

“After cutting the tree, we chip everything and put it in massive plastic bags. The bugs die eventually due to the [rise in] temperature. It also prevents the beetles [from spreading].”

Koos said they had already started monitoring three years ago, but only picked up the first infestation early in 2021. There are now 148 traps to monitor the population and spread.

Vergelegen put strict measures in place to avoid contamination, such as banning the transport of firewood onto the estate, and installing monitoring traps and repellent on the farm border, said Naidoo.

Historically important trees on the estate include five camphor trees planted more than three centuries ago and declared national monuments in 1942, and an English oak believed to be the oldest oak tree in South Africa.

“These are classed as champion trees and are protected by the National Forests Act 1998. Thus they represent the potential loss of part of the country’s arboreal and cultural history,” Roets said.

Given Vergelegen’s history and biosphere, a natural research lab is running an intensive three-year research project, said Roets, which conducts research at Vergelegen.

Their research has proved that chemical lures are crucial in keeping the infestations low at initial stages of invasion, and that some pesticide injections may slow down infection rates.

But not all trees react in the same way. In some cases these are not effective.

“Chemical control experiments have started and we will get our first results within the next two months,” said Roets. DM168


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The desire for equality must never exceed the demands of knowledge
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Lisbeth
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Re: Trees in South Africa are under attack. Why it’s proving hard to manage

Post by Lisbeth »

“Little is being done in Johannesburg, Durban, Makhanda, George. In Johannesburg, it has taken them four to five years to do anything.”
“They are only trees” 0= @#$ 0= @#$


"Education is the most powerful weapon which you can use to change the world." Nelson Mandela
The desire for equality must never exceed the demands of knowledge
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