South Africa steps up vigilance as Goss’s Wilt threatens maize industry
Experts urge farmers to prioritise strategies that limit disease spread, including crop rotation with non-host crops such as soya bean and small grains.
SOUTH AFRICA – South Africa’s maize sector is intensifying surveillance and disease-management efforts following recent detections of Goss’s wilt, a bacterial disease that has raised concern across the value chain.
Although the disease has not yet caused major yield losses locally, industry experts warn that its potential impact on production, regional trade, and national biosecurity remains significant.
Speaking to Farmer’s Weekly, Dr Mahlane Godfrey Kgatle, research coordinator at Grain SA revealed that while South Africa has not yet experienced major yield losses, the potential risk is significant, as Goss’s wilt can disrupt production, affect trade, and pose challenges for national biosecurity if it spreads unchecked.
Kgatle noted that the disease’s presence has already influenced regional trade dynamics. Goss’s wilt is regarded as a quarantine pathogen in many countries, and its detection prompted immediate reaction from neighbouring states.
“In January 2025, Botswana, Namibia, and Zimbabwe temporarily suspended maize imports from South Africa. Although these bans have since been lifted, they underscore the importance of managing the disease effectively to protect our reputation as a reliable grain supplier,” he said.
Locally, the pathogen has so far remained contained due to low inoculum levels and weather patterns that have not favoured its spread. Still, the industry is not taking its current status for granted.
According to him, if left unchecked, especially under conducive weather conditions, Goss’s wilt could spread widely and cause significant economic losses.
Strengthening on-farm control
Dr Henry Njom, researcher at the Agricultural Research Council (ARC), said no registered South African maize cultivars currently show resistance or tolerance to Goss’s wilt, unlike in the United States, where resistant genetics form the core of management.
Despite this gap, Njom stressed that South Africa’s recent encounter with the pathogen provides a “valuable window” for proactive intervention.
He urged farmers to prioritise strategies that limit disease spread, including crop rotation with non-host crops such as soya bean and small grains, avoiding mechanical injury during field operations, cleaning equipment between fields, and engaging seed companies about varieties that have shown tolerance elsewhere.
“These measures may seem basic, but they are crucial for keeping Goss’s wilt under control at this early stage,” he said.
Kgatle added that quarantine is not feasible for open-field crops such as maize. Instead, surveillance depends heavily on farmers reporting suspected cases.
“Isolating maize fields is nearly impossible, so we do not impose quarantine measures. Instead, farmers play a critical role by reporting suspected Goss’s wilt cases to Grain SA. These reports are vital for understanding disease distribution and severity,” he said.
National collaboration expands
A multi-institutional front has emerged to coordinate South Africa’s response. According to Yolanda Mthembu from the Directorate for Plant Health at the Department of Agriculture (DOA), this year’s national delimiting survey aims to map disease distribution with greater accuracy.
Grain SA and the Forestry and Agricultural Biotechnology Institute (FABI) have supported the initiative through field sample collection, strengthening diagnostic and surveillance efforts by FABI and the ARC.
“The data from these surveys will inform national monitoring and containment strategies. We aim to build a detailed picture of the disease’s distribution, the strains present, and the environmental factors that influence its spread,” Mthembu said.
To consolidate expertise, a Goss’s wilt research consortium has been established, coordinated by Grain SA and involving the ARC, the Council for Scientific and Industrial Research, FABI, the DOA, and the University of Pretoria.
Its objectives include collecting local Clavibacter nebraskensis samples, strengthening diagnostic systems, identifying suitable tolerant cultivars, improving knowledge exchange, and developing region-specific management guidelines.
“Collaboration across these institutions ensures that science-based solutions reach farms quickly,” Njom added.
Njom also highlighted the importance of accurate diagnosis. Symptoms of Goss’s wilt can resemble northern corn leaf blight, nutrient deficiencies, drought stress, or chemical injury.
Farmers are urged to watch for two key indicators: long grey-green lesions with wavy margins and dark freckles, and, in more severe cases, systemic wilt that leads to plant death.
Samples can be submitted to Grain SA, the ARC, FABI, Stellenbosch University’s Plant Disease Clinic, or the DOA for confirmation.
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