Cypress canker threatens exotic & native trees in SA

Sick cypress trees in Welkom, Free State. Scientists from Fabi fear that this disease could have serious impacts on native cedar trees in South Africa.

Cypress canker is killing exotic cypress trees in South Africa and poses a serious threat to native cedars, setting alarm bells ringing among members of the scientific community …

Welkom, the second-largest city in the Free State province of South Africa, is often referred to as a ‘city within a garden’ thanks to its numerous parks and trees. Unfortunately, many of these trees are dying from a disease known as ‘Cypress canker’.

Italian cypress (Cupressus sempervirens) is a popular ornamental tree that has been widely planted in Welkom, and is found on traffic circles, in parks, private gardens and along entire avenues in several neighbourhoods. Italian cypress is, however, also particularly susceptible to cypress canker.

The disease is caused by a number of fungal species in the Xylariales and specifically in the genus Seiridium. Symptoms include bleeding cankers that deform stems and cut off the water supply above the canker. As a result, diseased trees show typical “flagging” symptoms resulting in the death of affected branches.

Dr Janneke Aylward, a Research Fellow at the Forestry & Agricultural Biotechnology Institute (Fabi) based at the University of Pretoria, recently visited Welkom as part of a project to investigate the cause of cypress canker in South Africa. This project was prompted by the recent discovery of cypress canker on native Widdringtonia nodiflora cedar trees in South Africa, which poses a real threat to native cedar species.

During her visit Janneke, assisted by staff of the Matjhabeng Local Municipality’s Department of Parks, Sports and Recreation, took samples of diseased cypress trees at 11 sites across Welkom. She will isolate the canker fungus present in the diseased branches and investigate their identity and diversity.

Fabi research scientist Janneke Aylward … on the trail of Cypress canker in a bid to better understand the fungus pathogen that also poses a serious threat to native cedar trees in South Africa.

Native cedars at risk

According to Janneke, the presence of cypress canker in one of our native cedars - the Mountain cedar Widdringtonia nodiflora – has set the alarm bells ringing in scientific circles. The disease was recently identified in Mountain cedar at one site in Franschoek. To date the disease has not been found on Widdringtonia wallichi (Clanwilliam cedar) in the Cederberg, and the Fabi team has not yet visited the Baviaanskloof in the Eastern Cape to look for the presence of cypress canker in Widdringtonia schwarzii (the Willowmore cedar).

The Clanwilliam cedar is critically endangered and the Willowmore cedar is near threatened, according to IUCN. Janneke believes that these two cedars are only found in a very specific range, so the chances are good that they have had little or no contact with other cedars that may carry the disease.

Janneke believes that the Mountain cedar will survive the canker because it's a species that re-sprouts after fire. When the fynbos vegetation burns, the pathogen should be destroyed and the infected trees will likely re-emerge. The other two native cedars, the Clanwilliam cedar and Willowmore cedar, do not re-sprout so cypress canker - combined with the fact that their populations are already in decline - could have devastating consequences.

According to a recent article in the scientific journal, Plant Pathology, in July 2022: ‘Cypress canker has been known in South Africa for many decades, where it causes a serious disease on non-native species of Cupressus, but it has never been found on native Cupressaceae. The newly discovered disease caused by a probable alien pathogen is of particular concern because only three species of Widdringtonia occur in South Africa and they are important components of the native flora.’ (

Source Fabi News – All photos courtesy of Fabi.

A sick and dying Italian cypress in Welkom with a severe case of cypress canker fungus disease.
Janneke Aylward and Mike Wingfield of Fabi recently discovered the presence of the canker on Italian Cypress trees growing on the University of Pretoria campus.
Iconic Welkom cypress trees.

In search of a biocontrol for the Shot Hole Borer

Dr Wilma Nel and Garyn Townsend with collaborators in Vietnam collecting PSHB infested material.

Since it was discovered in KwaZulu-Natal in 2017, the Polyphagous Shot Hole Borer (PSHB) (Euwallacea fornicates) has spread rapidly into every province in South Africa except Limpopo, and has infested thousands of trees in urban areas, native forests and more recently in fruit crops.

This tiny invasive ambrosia beetle, native to Southeast Asia, has set alarm bells ringing as it is able to infest a wide variety of tree species – including seemingly strong, healthy trees - and is capable of spreading far and wide with the aid of human activity. It bores into the sapwood of trees and brings a damaging fungus, Fusarium euwallaceae, along with it.

The economic impact of PSHB in South Africa is still in its infancy, but is expected to run into the billions if allowed to continue unchecked. The environmental impacts are also potentially huge as a number of native trees are susceptible to infestation.

The Polyphagous Shot Hole Borer … pest invader spreading rapidly across South Africa.

One of the management options being explored by scientists at the Forestry and Agricultural Biotechnology Institute (FABI) at the University of Pretoria, is to identify a natural enemy of PSHB in its native range and then introduce it into South Africa where it could play a role in controlling the PSHB population.

This led to a recent trip to northern Vietnam by Prof Brett Hurley and Dr Wilma Nel of FABI and PhD candidate Garyn Townsend to collect material from trees infested by PSHB with the aim of finding, identifying, rearing and testing natural enemies. The visit was highly successful and the team brought PSHB-infested Acacia back to the FABI quarantine facility, after obtaining the required permits from South Africa and Vietnam.

The plan is to monitor the material for the emergence of natural enemies, specifically parasitoids, which could be reared and deployed in South Africa to serve as an effective biocontrol agent for PSHB. This is a lengthy process that involves extensive testing to ensure that the introduced species is sustainable and does not cause any collateral damage to native species in South Africa.

Prof Brett Hurley, Dr Wilma Nel and Garyn Townsend with collaborators at the Vietnamese Academy of Forestry Sciences in Hanoi, Vietnam.

The project has been made possible through the funding of the Department of Forestry, Fisheries & the Environment and through collaboration with the Vietnamese Academy of Forestry Sciences, specifically Prof Pham Quang Thu.

According to a recent article in the South African Journal of Science by a group of FABI scientists, the South African PSHB invasion represents the largest outbreak of this beetle in its invaded range anywhere in the world. It has infested 130 plant species in urban, agricultural, and native ecosystems in South Africa, including 44 previously unreported hosts.

In South Africa, PSHB is currently mostly confined to urban environments, but its presence has also been confirmed in the natural forests around Knysna and George where it is feared it could do extensive environmental damage.

Virgilia oroboides, a native tree species found in the southern Cape natural forests, is a reproductive host for PSHB.

PSHB infected tree showing damage from the fungus.

“It is an important pioneer forest species in the southern Cape that protects forests from severe climatic fluctuations and fire and houses a large number of native organisms. Elimination of this single species could have irreversible consequences for native forest integrity,” the scientists write. 

PSHB control measures using pesticide sprays have been effective in laboratory conditions, but are currently not considered practical in the wild. Deployment of a biocontrol agent looks to be the best management option at this stage, provided a suitable candidate can be found, and the necessary authorisation for its release in South Africa obtained.

The only agricultural crops that appear to be affected by PSHB so far are pecan and macadamia, but they are not reproductive hosts and so the impacts are expected to be limited. Other orchard crops that may be vulnerable to PSHB are cherry, apple, citrus, peach, guava, olive, grape and prune crops.

Initial surveys in invaded urban areas of Johannesburg, Knysna, George and Somerset West indicate that a high percentage of English oak, London plain trees, box elder and other maples will die when infested by PSHB. The cost of disposing of these urban trees and replacing them will be considerable.

Urban trees play a vital role in providing shade, moderating temperatures and creating an attractive environment that enhances the quality of life and boosts the hospitality and tourism sectors. They also provide refuge for numerous birds and insects.

The team in the quarantine facility at FABI, University of Pretoria, where the collected material is being monitored for emergence of natural enemies of PSHB.

How to detect PSHB infestation

The first signs of PSHB infestation are the presence of tiny holes penetrating the bark of trees and leading directly into the sapwood. These random holes, less than 1mm in diameter, look a bit like they could have been caused by shotgun pellets – hence the common name ‘shot hole borer’.

Lesions, wet patches and gum exudation may be visible on the outside of the tree, and a pinkish-brown stain caused by the associated fungusmay be seen spreading from the gallery into the vascular tissues below the bark. PSHB colonisation of reproductive hosts often results in wilting and death of the infested branch - or the entire tree.

The FABI team has had a lot of success with the introduction of biocontrol agents for a number of tree pests in South Africa in the past, and this experience will be invaluable in finding an effective biological enemy for PSHB. The stakes are high as this tiny hitchhiking beetle continues to spread across southern Africa.

Typical Eucalyptus plantation in Vietnam.


FABI News;

Article by W. Nel, B. Slippers, M. Wingfield, N. Yilmaz & B. Hurley in South African Journal of Science, April 2023

All photos courtesy of FABI.

Using drone & satellite to track pest damage

FABI and ICFR researchers are collaborating in an innovative project to develop a system to monitor the impact of the Eucalyptus snout beetle on the health of eucalypts using a combination of drones and satellite remote sensing.

Gonipterus sp. n. 2, is an invasive insect native to Australia and a significant defoliator of Eucalyptus. Management of this pest, commonly known as the Eucalyptus snout beetle, relies mainly on classical biological control by a tiny wasp Anaphes nitens, which was first introduced into South Africa in 1924. The biological control has been effective in keeping Gonipterus infestations under control for decades, but in the past few years Gonipterus infestations have increased and the damage to eucalypt plantations in South Africa is on the rise.

The project is a collaboration between the Forestry and Agricultural Biotechnology Institute (FABI) based at the University of Pretoria, the ICFR’s Dr Ilaria Germishuizen and Dr Benice Sivparsad and international researchers Prof Wouter Maes of the University of Ghent in Belgium and Dr Rene Heim of the Institut für Zuckerrübenforschung.

The use of a drone to measure Gonipterus damage is key as it provides very high resolution images of the tree canopy that cannot be seen from ground level once trees reach more than 2 m height. The satellite imagery is useful in that it can detect canopy damage but is not fine enough to provide the detailed information that the researchers require.

The project has two main objectives:-
• To use satellite and drone imagery to assess and monitor the extent of canopy damage from Gonipterus.
• To understand the relationship between the canopy damage and the productivity of the compartment, which will provide forest managers with the info necessary for them to decide when and where to incur the costs of applying a chemical spray to reduce Gonipterus infestations. The info gathered from the study will also enable the researchers to assess the impact of a chemical spray application on the population of the biological control agent A. nitens.

The model that will be developed through this study will be applicable to monitor the impacts of other pests and diseases that defoliate eucalypts.

Earlier this year PhD candidate Phumlani Nzuza, Dr Michelle Schroder and Ofentse Mathibela from FABI went to the KwaZulu-Natal midlands to map Gonipterus sp. n. 2 defoliation levels using their newly acquired drone. For field ground truthing they are using ICFR’s Gonipterus impact trials at Hodgsons (Greytown) and Sutton (Ixopo)

The ICFR’s work is supported by FSA, Sappi, NCT and TWK.

SA researchers push the innovation envelope

​Three South African researchers have made it to the global shortlist of the Blue Sky Young Researchers and Innovation Awards.

The awards, launched in 2016 by the International Council of Forest and Paper Associations (ICFPA), aim to recognise, celebrate and promote innovations in the global forestry sector.

Justin Phillips and Hester Oosthuizen, both from the University of Pretoria, and Eddie Barnard from Stellenbosch University, go up against another 18 of their peers from around the world. The top three finalists will win cash prizes and get an opportunity to present their work at the ICFPA’s Global CEO Roundtable virtual discussion on 29 April.

Particle board from paper sludge
Eddie Barnard is exploring the commercial viability of using technical lignin (a by-product from the wood pulping phase in pulp or paper making) and pulp and paper sludge (rejected, degraded, and spilled fibres and water from the pulping and paper making processes) to make composite materials.

Lignin has binding properties, which when combined with sludge, could be used to make construction materials such as a replacement for particle board. The use of lignin together with pulp and paper sludge could replace components that would otherwise be produced from fossil-based resources, and reduce associated waste, greenhouse gas emissions and disposal costs.

Cattle dip for killing ticks 
Justin Phillips has looked at how starch and nano-cellulose can be used as a carrier material for pesticide application in the agricultural sector. The insoluble solid active ingredient in the pesticide attaches to the carrier, which is water-soluble and allows for safer and more efficient and safe controlled release of the pesticide, especially in aqueous environments such as animal dipping for tick prevention.

A substitute for petroleum-based plastics
Cellulose is uniquely positioned to substitute many petroleum-based plastics, however it cannot be melt-processed and dissolved using common organic solvents. This is why Hester Oosthuizen examined the efficacy of using choline chloride and ionic liquids, considered greener and less volatile, to make cellulose fluid enough to produce cellulose-based materials using existing polymer processing techniques.

“We are immensely proud of our finalists for making it this far, and demonstrating that South Africa can hold its own against the best in the world,” says Jane Molony, executive director of the Paper Manufacturers Association of South Africa (PAMSA). “As a sector we constantly look for ways to support young people with an interest in science and technology and are proud of the career opportunities our member companies can offer them.”

Wood – a renewable alternative to conventional materials
As a sustainably farmed resource that stores carbon, wood is increasingly being used not only in the built environment for houses and high-rises, but also for its cellulose, lignin and sugars. These elements all have a role in helping the world find renewable and low-carbon alternatives to the likes of plastic, chemicals, steel and concrete.

“Two key advantages that commercially farmed trees bring are their renewability and their carbon storage,” explains Molony. “The fact that trees are sustainably planted, harvested and replenished on the same land makes both wood and paper products renewable and efficient resources. For a low carbon future, it’s tremendously exciting – especially when we look at the kind of research our young scientists are producing.”

An international panel with connections to industry, academia and public policy has been assembled to judge the awards, including:
• Lyndall Bull, Forestry Officer at the Food and Agriculture Organisation of the United Nations (UN)
• Barbara Tavora Jainchill, Programme Management Officer, Forest Affairs, with the UN Forum on Forests Secretariat
• Fernando L. Garcia Bertolucci, Executive Director of Technology and Innovation at Suzano S.A. and Member of IUFRO
• Professor Gil Garnier, Director of BioPRIA within the Department of Chemical Engineering at Monash University
• John Innes, Dean of the Faculty of Forestry at University of British Columbia.
The local round was adjudicated by Valeske Cloete (Mpact), Sanet Minnaar (Sappi) and Mike Nash, former head of PAMSA’s Process Research Unit and experienced chemical engineer.

Related article: ICFR lab offers new opportunities for research and innovation