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What to look for and collecting samples

Disease infection and spread

Ceratocystis species are fungal pathogens that affect mostly woody plant species.

Infection occurs through natural openings (buds, cracks in bark, root knots etc.) or external wounds on the stems or roots, induced through cultivation practices (e.g. grafting and pruning wounds), insects or weather-related conditions. The fungus invades the plant and blocks the water transport system resulting in wilting symptoms.

The spores of the fungus can be distributed via insects (e.g. picnic beetles or flies) by attaching to the insects which then transmit these spores from diseased to healthy plants. Some insect vectors bore into the diseased tissue of plants and the contaminated frass (borings) can be distributed via wind and rain.

Spread also occurs through the movement of infected plant material and soil. The thick fungal spore form can survive for long periods of time in the soil and infect new plants planted in the same soil.

Symptoms

Symptoms of infected plants include leaf discolouration (yellowing) and wilting (a) which can eventually lead to plant death (b). 

Internal infections in the cane/trunk are visible as dark brown streaks or mottled spots in the wood(c,d,e,f,h) or roots (g).

Ceratocystis wilt in Kiwi

Collecting samples for diagnosis

When wilting symptoms appear, inspect both rootstock, especially at the soil level, and recently wilted canes. Cutaway bark and look for streaking of wood (c,d,e,h).

Cut infected cane tissue at the margins of healthy and dying tissue or shave off thick pieces of discoloured wood with symptoms. Wrap samples from individual plants separately in newspaper and place them in separate plastic bags. Document variety number on bags. If roots are infected, first wash off soil and dry samples before wrapping in newspaper. 

Take clear photos of symptoms (use images here as examples).

If any symptoms are seen at the root collar, take soil samples. Mix up the soil (top 10cm) from around the base of the plant. Place ONE CUP of this soil in a plastic bag and seal firmly.

Send samples by COURIER to:

Dr Lieschen De Vos, (c/o Prof Irene Barnes/Prof Mike Wingfield)

Forestry and Agricultural Biotechnology Institute (FABI)

University of Pretoria

Lunnon Street Entrance

Hatfield

Pretoria

0083

Tel: 012 420 3938

Email: This email address is being protected from spambots. You need JavaScript enabled to view it. with courier tracking number, details and extent of the problem, photos, farm/collector details and contact numbers.

For more information on the FABI Diagnostic Clinic, please click here.

Download the pamphlet here

 

Text prepared by: Irene Barnes, Mike Wingfield

Photos by: Malcolm Deacon, Jolanda Roux and Irene Barnes

 

In the Applied Mycology Research Programme, we are focusing on to better understand the fungal communities that produce mycotoxins in agricultural crops, food and animal feed. Emphasis is placed on the diversity and taxonomy of genera such as Alternaria, Aspergillus, Fusarium, Penicillium and Talaromyces, but many others are also studied.  Ultimately, our goal is to secure food and feed from farm to fork for future generations.

The research group focusses on the interaction between cereal plants and foliar fungal pathogens. Pathosystems currently under study include grey leaf spot in maize (GLS) caused by Cercospora zeina, and northern corn leaf blight (NCLB) in maize and sorghum caused by Exserohilum turcicum. Projects are aimed at studying population structure of these pathogens, identification and functional characterisation of pathogen effectors causing disease, and cereal plants’ response to pathogen infection.

The Crop Floral Biology and Environments research team is focused on understanding how changing environments affect floral development, anthesis (flowering from bud opening to pollination) and pollination in economically important crops such as maize and sunflower. The multidisciplinary projects draw together aspects of climatology, plant physiology, plant molecular biology and ecology to holistically address these questions.

The CTHB promotes the health of trees indigenous to South Africa through the use of biotechnology. This is accomplished through projects that typically consider the pathogens and pests associated with native trees and woody hosts. The CTHB also explores the possible effects that factors such as climate change, society, natural forest health and plant genetics may have on the health of native woody resources and ecosystems.

 

The Grain Research Program (GRP) is a newly established programme that was developed by a team of multidisciplinary grain researchers from different institutes and programmes at FABI and elsewhere in South Africa. The GRP was formed to engage directly with grain stakeholders to initiate research that will support this sector by identifying future challenges to the industry and exploring solutions to these challenges. To its stakeholders in agriculture, the GRP also provides extension and disease/pest diagnostic services.

The Molecular Plant Physiology group collaborate with research groups in the UK, USA, Canada and Belgium to study the effect of biotic and abiotic stress in plants though a combination physiology, phenomics, functional genomics and proteomics. Using a holistic approach we aim to better understand the mechanisms underlying plant stress tolerance and resistance as well as the identification of potential biological markers that can then be used in plant improvement.

The Molecular Plant-Pathogen Interactions (MPPI) Group is located in the Plant Sciences Complex at the University of Pretoria and is headed by Prof Dave Berger. Research focuses on the molecular basis of plant-pathogen interactions using a range of approaches from whole plant phenotyping to functional genomics. We study the maize – grey leaf spot (Cercospora zeina) pathosystem.

The group is actively involved in seed science research. Our research fields include seed health tests, general seed pathology, seed vigour and seed germination according to ISTA rules. We are also involved in evaluating industry, or developing novel, environmentally sustainable, seed treatments. The research focuses on grains, herbs and vegetables.

The bacterial genomics and host pathogen interactions research group is interested in understanding molecular pathogen-host interactions between potato plants and their various pathogens. The objectives of the research include molecular identification of potato pathogens and pests, functional characterisation of bacterial virulence factors and elucidation of potato plant responses elicited by potato pathogens. We ultimately endevour to contribute knowledge toward the control of pathogens and pests under study.

The primary research focus of the Potato Pathology Programme is the epidemiology, diagnosis and control of soil- and seed-borne diseases of potatoes. Diseases currently being investigated include powdery scab, black scurf, stem canker, blackleg and soft rot. Various approaches are used to better understand disease spread and development, host-pathogen interactions and control, to provide growers with risk assessment and disease management strategies.  

 

 

Avocado Research Programme, a programme of the Forestry and Agricultural Biotechnology Institute (FABI), represents a cooperative venture between The Hans Merensky Foundation and the University of Pretoria, to deal with avocado disease problems, especially the avocado/Phytophthora cinnamomi interaction. HMF has committed a substantial amount to establish this research project at FABI and The University of Pretoria in turn provides the infrastructure necessary to conduct research.

 

The CTHB promotes the health of trees indigenous to South Africa through the use of biotechnology. This is accomplished through projects that typically consider the pathogens and pests associated with native trees and woody hosts. The CTHB also explores the possible effects that factors such as climate change, society, natural forest health and plant genetics may have on the health of native woody resources and ecosystems.

 

The Kiwifruit Protection Programme (KPP) was established in February 2023 as a collaborative initiative between the South African Kiwi Growers Association and the Forestry and Agricultural Biotechnology Institute (FABI). This programme, under the primary leadership of Prof. Irene Barnes, aims to support local kiwifruit farmers by conducting research on pests and diseases of kiwifruit and providing an extension and disease/pest diagnostic service to the farmers.

Macadamia is one of the fastest growing agricultural industries in the country and is of economic importance to South Africa. The industry is however hampered by a number of pests and diseases which can cause major economic loss, both in terms of yield as well as nut quality. The industry currently relies heavily on the use of commercially available pesticides and chemicals for pest and disease control. There is, however, growing concern regarding continuous build-up of resistance, and the long-term sustainability of the industry is dependent on the use of integrated pest management.

The Phytobacteriology programme at FABI has two main research areas, viz. taxonomy and pathogenicity. Several plant pathogenic bacteria are currently being characterized using a range of techniques, and are also being formally described. As one of our main focus areas, the pathogenicity factors of Panteoa ananatis, an opportunistic plant pathogen, are being investigated using a functional genomics approach.

New Publications

Pham NQ, Wingfield BD, Marincowitz S, Brawner JT, Hulcr J, Wingfield MJ. (2025) Cryphonectria canker on Eucalyptus in Florida reconsidered. Forest Pathology 55:e70031. 10.1111/efp.70031
Nzuza P, Schröder ML, Heim RJ, Daniels L, Slippers B, Hurley BP, Germishuizen I, Sivparsad B, Roux J, Maes WH. (2025) Assessing Gonipterus defoliation levels using multispectral unmanned aerial vehicle (UAV) data in Eucalyptus plantations. Ecological Informatics 90:103301. 10.1016/j.ecoinf.2025.103301
Kunene S, Mmushi TJ, Steenkamp E, Motaung T. (2025) Pinus-derived membrane vesicles disrupt pathogenic metabolism in fungi. plant biology 10.1111/plb.70069 PDF
Theron CA, Wingfield MJ, Ahumada R, Carnegie AJ, Fraser S, Rodas C, Barnes I. (2025) Diversity and distribution of Lophodermium species on non-native Pinus species in the southern hemisphere. Mycological Progress 24(44) 10.1007/s11557-025-02056-5
Msweli D, Geerts S, Nndanduleni M, Paap T. (2025) Evaluation of phosphite to protect a South African Proteaceae from Phytophthora root rot. Journal of Plant Pathology 10.1007/s42161-025-01945-8 PDF