The Department of Agriculture, Agrarian Reform and Rural Development (DALRRD) of the Republic of South Africa has recently alerted the agricultural community, importers, international travelers, academic institutions and all citizens about the potential risk facing the country, Southern African developing countries (SADC) and the entire continent as regards Asian citrus greening (HLB), Candidatus Liberibacter asiaticus.

Asian citrus greening is the most devastating citrus disease in the world, and currently does not occur in sub-Saharan Africa. However, the Asian citrus psyllid (ACP) has been detected and is spreading in east-central Africa, and Huanglongbing (HLB) is already found in Ethiopia, Kenya, Mauritius and Reunion. Both HLB and ACP occur in countries that are frequent trading partners with southern African countries, traders and travelers pose a threat of inadvertent spread of the disease or vector.

Asian Citrus Greening is a bacterial disease caused by Candidatus Liberibacter asiaticus and is transmitted by the Asian Citrus Psyllid (ACP) insect vector, Diaphorina citri. Symptoms on leaves and shoots include yellow shoots, asymmetrical, mottled leaves, small upright chlorotic leaves, out-of-phase flushing, and branch dieback. Flower and fruit symptoms include intense, non-seasonal flowering on diseased branches, small, crooked, bitter-tasting fruits with small, brown, aborted seeds, and uneven coloration at maturity and excessive fruit drop. Sooty mold growth resulting from excess molasses production can also affect the plants' ability to photosynthesize, which can affect the overall health of the plant. Production costs would increase due to the need to control this pest. Market access, the economy, the citrus and nursery industry, and backyard citrus production would also be adversely affected.

Considering the socio-economic value and impact of citrus production in the country, the South African Government warns that this pest must be taken seriously because citrus contributes enormously to job creation and economic growth. The citrus industry is the third largest horticultural industry after deciduous fruits and vegetables; and is mainly aimed at the export market. The industry contributed more than 20 billion Rand (more than 1.087 million euros) to the total gross value of South African agricultural production during the 2016/17 production season. It is a major source of foreign exchange and employs more than 120,000 people.

Therefore, the South African authorities have indicated that "any introduction, spread and establishment of this disease in the SADC region and / or our country will generate immeasurable pressure for the citrus industry, given the other diseases and phytosanitary pests with the that the citrus industry is fighting, such as citrus black spot, false apple moth and fruit flies. "

The disease can be transmitted by the vector insect, as well as by infected plant material. Prevention, early detection and rapid response will involve a coordinated approach between DALRRD, Provincial Departments of Agriculture (PDA) and industry to ensure that producers are protected as much as possible from this disease.

The National Plant Protection Organization of South Africa (NPPOZA), within DALRRD, is already developing an early warning system (EWS) for this pest in collaboration with the citrus and FLW industry. This is in line with the South African Emergency Plant Pest Response Plan (SAEPPRP). More actors will be addressed in the development of the SAT, to ensure that all relevant state bodies are included, as well as research organizations, commercial, small-scale and subsistence producers.

International travelers and the business community are advised not to import host plant nursery material from any country into South Africa without following the necessary import procedures, as this may pose a threat of inadvertent spread of the disease or vector and may be requires growers to contact DALRRD in the event of any suspicious-looking symptoms on citrus trees and fruits.