A perspective on plant quarantine

Plant quarantine is an essential link in the plant-production chain and a crucial component of plant improvement. By Kyra-Kay Rensburg.

“Importing plant material from other countries provides an opportunity to also import exotic pathogens that can have potentially devastating consequences, not only for the agricultural industry but also on a larger ecological scale,” explains Rachel Kriel, manager of PlantSA.

According to Kriel, growers should be mindful of the risks of importing plant material or fruit contaminated with regulated pests or diseases. She cites the example of plum pox virus. This virus entered the United States illegally in material propagated outside their certification system.

By the time the first symptoms were identified, the virus had already spread to certified trees in orchards, leading to the removal of large numbers of stone-fruit trees, says Kriel. “Propagation material illegally entering the country can harbour many a threat that will most likely only be discovered when it is too late to stop it from spreading.”

Plum pox is just one example of a devastating disease not yet reported from South Africa — plant quarantine aims to prevent such diseases as well as pests from entering the country.

Plant quarantine in South Africa

The Department of Agriculture, Land Reform and Rural Development serves as the National Plant Protection Organisation for South Africa. Their responsibilities include protecting agriculture from exotic pests and diseases, and ensuring safe agricultural trade.

To achieve this, they offer plant quarantine and diagnostic services based on the principles of the World Trade Organisation’s Sanitary and Phytosanitary Measures of detection, identification, and interception of pests and diseases of quarantine importance.

“Plant material entering the country on a legal import permit is inspected and tested while kept in a post-entry quarantine facility,” says Kriel. “Once proof is obtained that the material is free of any regulated quarantine pests, it can be released to the importer for propagation.”

According to Hugh Campbell, Hortgro Technical Manager, new cultivars are brought in as either tissue-cultured material or budwood. “Buds are grafted onto clean, certified rootstocks. The trees are kept in greenhouses where tests are performed to ensure they are free of regulated exotic pests and viruses.”

Campbell believes that viruses are the most significant concern. “Once they’re here, they’re here forever,” he stresses.

If imported plant material tests positive for any regulated pest or disease, the importer is notified and can choose to have the plant material destroyed or treated. Treatment options include fumigation and thermotherapy, depending on the type of pest or disease.

In addition to preventing the entry of exotic pests and diseases, quarantine also ensures that plant material and products leaving the country are free of pests and diseases that could potentially block future exports from South Africa if the importing country’s requirements are not met.

Speeding up the process

The traditional route of obtaining plant material requires plants to be quarantined for two or more years. In the worst cases, plant material might need to be re-imported over several years, to the disadvantage of producers. “Everyone wants trees of new varieties as soon as possible,” comments Kriel.

According to Kriel, an import process that provides risk-free propagation material in the shortest time could allow producers to evaluate new cultivars properly under local conditions. This reduces the risk of investing in orchards that fail to perform.

“There are a number of countries with very strict quarantine requirements,” says Kriel. “In many of these countries, the quarantine services are combined with certification, not only preventing the entry of harmful organisms but also preventing the spread of non-regulated pests of economic importance.”

Accrediting international facilities allows importing low-risk certified material that meets all the local quarantine and scheme requirements. This means that imported plant material can be released faster as extensive retesting is not required.

“Imported varieties with low or no phytosanitary risk can also be multiplied even before being released, which will provide an opportunity to evaluate the variety in the shortest possible period,” says Kriel. This allows for quick access to new cultivars that give growers a competitive edge.

This is why one recommendation of the recent South African plant improvement benchmarking was to support the accreditation of international facilities. For more about the task team’s findings around best practices for quarantine, read the article on Benchmarking South African plant improvement elsewhere in this issue.

Image: From left to right: Nolan Africander, DALRRD; Rachel Kriel, PlantSA; Hugh Campbell, Hortgro.

Supplied by Hortgro.