Concerns about the dangers of avocado sunblotch viroid (ASBVd) are mounting in South Africa’s avocado industry, with experts urging growers to enforce strict biosecurity measures in nurseries to contain this microscopic threat.

By Jasper Raats, Senior Journalist at African Farming and Landbouweekblad

ASBVd is a single-stranded circular RNA molecule that infects avocado trees, causing so-called avocado sunblotch. The infection spreads through contaminated plant material, seeds, pollen and even pruning tools – and there is currently no remedy.

Infected trees often display discoloured, sunken spots or streaks on fruit, and deformed leaves. Even when symptoms are not visible, yields can drop drastically, severely affecting the crop’s commercial value.

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‘Prevention Starts at the Nursery’

According to Kobus Eloff, general manager of Du Roi Halls Nursery in Mbombela, the company’s biosecurity strategy is designed to protect both the industry’s reputation and its export market access.

“That’s why every mother tree from which grafting wood is sourced is tested annually for ASBVd – not just every three years as required by regulations,” he says. “In addition, we conduct random tests throughout the year.”

Each genetic block in the nursery is physically separated, with root zones sealed off to prevent potential cross-contamination. Seed management is handled with equal care, Eloff adds. Seeds are sourced exclusively from trusted international suppliers and from a local seed orchard outside Mbombela, which is surrounded by crops that do not attract bees, thereby preventing pollen transfer.

Eloff emphasises that these measures go beyond mere compliance – they are essential for the sustainability of the entire industry.

Producers are encouraged to use plant material only from nurseries that are certified by the South African Avocado Growers’ Association (SAAGA) and accredited by

Producers are encouraged to use plant material only from nurseries accredited by the Avocado Nurserymen’s Association (ANA) under the auspices of the South African Avocado Growers’ Association (SAAGA).

“Every infected tree planted poses a risk to an entire farm and even to surrounding farms,” Eloff warns. “Prevention starts at the nursery, and farmers have the right to insist on the highest standards.”