South African soya bean harvests under threat from fungal pathogen

Dr Godfrey Kgatle, research coordinator at Grain SA, has warned that the seed-borne fungus Cercospora kikuchii is threatening soya bean production across the country. Octavia Avesca Spandiel reports on the diseases it causes, the risks of using untreated seed, and how certified seed and early monitoring can help farmers protect their yields and grain quality.

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In 2024, South African soya bean farmers battled an aggressive resurgence of Cercospora kikuchii, a fungus that caused three crop diseases: Cercospora leaf blight, purple seed stain, and pod and stem blight.

Dr Godfrey Kgatle, research coordinator at Grain SA, said the fungus, widespread across all production regions in the country, proved especially damaging due to its ability to survive in infected seed, and resurface in the next planting season.

RISK OF USING UNTREATED SEED

Kgatle added that the most severe yield losses were recorded among farmers who used seed from a previous crop that was infected or planted untreated or poor-quality seed. These practices increased the risk of disease transmission and encouraged fungal build-up in the field. “Farmers who do not use certified or treated seed are the most vulnerable to losses. They risk purple seed stain, leaf blight, and pod and stem blight, all of which reduce seed quality and yields,” he said.