Department warns farmers of citrus disease

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Also known as Huanglongbing (HLB), Asian Citrus Greening disease is caused by the bacteria, Candidatutus Liberibacter asiaticus, which is an insect vector-transmitted by the Asian citrus psyllid (ACP), Diaphorina citri, and it poses a huge threat to all citrus industries in the world.

Symptoms on leaves and shoots include yellow shoots; asymmetric, mottled leaves; small upright chlorotic leaves; out of phase flushing, and branch dieback.

Flower and fruit symptoms include unseasonal and heavy flowering on diseased branches, small, lopsided, bitter-tasting fruit with small, brown, aborted seeds and uneven colouring at maturity,and excessive fruit drop.

"The sooty mould growth resulting from excess honeydew production can also affect the plants’ ability to photosynthesise, which can affect overall plant health," the department said in a statement.

Although not present in South Africa currently, the department warned that Asian Citrus Greening poses a serious threat to the citrus production in South Africa, the Southern African Development Community (SADC) region and the entire continent.

"It is the most devastating disease of citrus worldwide, causing serious yield losses to producers in countries where it currently occurs. On the African continent, this specific strain has already been detected in Ethiopia and Kenya, and the insect vector has been detected in Kenya and Tanzania.

"The occurrence of this disease, together with its primary vector, is a major concern to the continent because infected citrus trees cannot produce edible fruit and will decline and die, thus, it is a major concern for food security and the loss of market access due to a major loss in the production of required fruit volumes," the department said.

Considering the socio-economic value and the impact that citrus production has in South Africa, the department said it is imperative for all role players, including farmers, nurseries, international travellers, importers, researchers and members of the public to adhere to the country’s phytosanitary regulatory framework.

"This will minimise the introduction, establishment and spread of this disease in South Africa and the SADC region. The introduction of this disease in the SADC region will have devastating consequences for the citrus industry, which is already under immense pressure, dealing with other economically important pests and diseases, such as Citrus black spot (CBS), False codling moth (FCM) and fruit flies (FF)," the department said.

Preparedness and Response Action Plan

The department, in collaboration with the citrus industry, has since established an HLB Steering Committee, which has developed a Preparedness and Response Action Plan and related measures to minimise the risks of the introduction of HLB and ACP in South Africa.

Minister Thoko Didiza has approved and published the relevant Control Measures in the Government Gazette No. 44188 R. 121 of 12 February 2021, in accordance with the provisions of the Agricultural Pests Act, 1983 (Act No.36 of 1983).

These regulatory interventions are to ensure preparedness and response to any possible introduction, establishment and spread of the disease.

The department said that a national survey to enhance the chances for early detection of the disease, as well as the vector, forms part of the strategic plan of the department.

Departmental officials have also met with their counterparts in Kenya, to map a way forward on how to deal with HLB and ACP in Kenya and to minimise its introduction into Southern Africa.

"It is imperative that all role-players involved in the citrus industry observe all precautionary measures in terms of the relevant legislative prescripts to help minimise the risks of introduction of Asian Citrus Greening and its primary vector Asian citrus psyllid into South Africa.

"The importers of plants and plant products must follow all the proper import procedures in terms of the Agricultural Pests Act, 1983 (Act No. 36 of 1983), to help minimise the introduction, establishment and spread of any potential harmful species in the country," said the department.