With Asian citrus greening causing havoc in numerous growing areas around the world, South Africa is working hard to keep the region free of the pathogen and refining protocols in case it is ever detected.

The disease, also known as Huanglongbing (HLB), is a major problem in places like Brazil and the U.S. state of Florida, where it has severely damaged the industry. 

HLB, which has a number of impacts on tree health, is easily spread by moving infected plants and through its most effective vector, the Asian Citrus Psyllid (ACP).

Citrus Growers Association (CGA) of Southern Africa CEO Justin Chadwick said that at the Citrus Research International's (CRI) recent Citrus Research Symposium, it had been indicated that it was not a question of 'if' the disease would one day find its way into the country, but 'when'.

Paul Fourie, manager of the CRI division called the Southern African Citrus Improvement Scheme (CIS) and associate professor in plant pathology at Stellenbosch University, said the industry had a range of initiatives to prevent an incursion.

"Whilst HLB and ACP do not occur in South Africa, we are very much aware of what is happening in some other parts of the world with HLB, and the huge threat it poses," he said in a statement sent to www.freshfruitportal.com.

"We are therefore working on our own preparedness plans. We have close links with the Brazilian, Floridian and Californian citrus industries, and learn from their experiences.

"HLB is being managed in Brazil using a three-pronged approach, one of which is production and supply of disease-free nursery trees (i.e. “start clean”)."

Fourie said additional initiatives were currently being discussed with industry stakeholders following a recent review of the CIS, with measures specially targeted at propagation material supply to citrus nurseries and citrus tree production.

"Similar to the initiatives in California, we are investigating the proactive changeover to production of propagation material and nursery trees in insect-protected structures," he said.

Fourie highlighted the Citrus Biosecurity in Southern Africa initiative, which includes engagement with countries in the region and promotes the use of disease-free citrus propagation material from the CIS, instead of the direct import of nursery trees from countries where harmful diseases could be present.

The expert also said current measures were being strengthened to control any damage should the disease one day be detected in South Africa.

"The South African citrus industry has developed an HLB/ACP Action Plan with our national Department of Agriculture, Forestry and Fisheries [DAFF] as a contingency measure against incursion of either the bacterium or its vector," he said.

"This plan includes awareness, surveillance and regulatory procedures regarding containment/quarantine and eradication actions."

He added that following the 'expanding threat' of HLB, as well as the lessons learnt from Brazil, Florida and California, it was clear that effective plans should have 'specific, well-defined and unambiguous protocols for all actions'.

"Ideally, these should be communicated and accepted by all stakeholders to prevent any delays in controlling the spread of the disease or its vector. Further refinement of our Action Plan is one of our immediate priorities," he said.

"South Africa has also initiated research into control of ACP with collaborators in Mauritius, using chemical control methods that were proven to be effective against the vector of African Greening, which is endemic in South Africa."

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