EFSA issues urgent advice on plant bacteria Xylella fastidiosa
The European Food Safety Authority (EFSA) has concluded that focusing on the trade of plants intended for planting and on the presence of infective insects in plant consignments would be the most effective ways of limiting the spread of the bacteria Xylella fastidiosa that has recently been detected in Southern Italy, the first outbreak of its kind in the European Union.
Transmitted by certain types of sap-sucking hopper insects, the bacteria X. fastidiosa, has been identified in the current disease outbreak that has affected 8000 hectares of olive trees in the Puglia region of Southern Italy. The bacteria can be hosted in a very broad range of plants including almond, peach, plum, apricot, grapevines, citrus, coffee and olive as well as oak, elm, Ginkgo and sunflower. Importantly, plants can carry the bacteria without showing signs of disease. X. fastidiosa is regulated as a harmful organism in the European Union (EU), whose introduction into, and spread within, all Member States is banned.
In light of the current outbreak, the European Commission requested EFSA to provide urgent scientific advice outlining the list of known plant hosts, identifying the different ways that infected plant species and carrier insects could enter the EU as well as identifying and evaluating possible preventative measures.
Plant health experts at EFSA have concluded that X. fastidiosa has a very broad range of known host plants in the EU, including many grown for agricultural production as well as indigenous wild species common in Europe. Additionally, there are a large number of species that could potentially be infected by the bacteria but have never been exposed, making it difficult to establish what the likely impact would be. Importantly, the sap-sucking hopper insects found in the EU that could potentially carry the disease are likely to have different feeding habits and patterns.
As the only natural means for spreading X. fastidiosa is by the sap-sucking hopper insects that generally can fly short distances of up to 100 metres, movement of infected plants for planting is the most efficient way for long-distance dispersal of X. fastidiosa. In addition, the transport of the insects that carry the bacteria in plant shipments and consignments has been identified as a concern.
The main source of X. fastidiosa into the EU is therefore trade and thereafter the movement of plants intended for planting. Other potential sources of infection were assessed including fruit, wood, cut flowers, seeds and ornamental foliage. However, these were considered either negligible or low in terms of potential pathways for introduction of the bacteria.
There is no record of successful eradication of X. fastidiosa once it has been established outdoors. EFSA therefore recommends that preventative strategies for containment of outbreaks should focus on the two main routes of infection (plants for planting and infective insects in plant consignments) and be based on an integrated system approach.
Following this rapid assessment, EFSA’s Plant Health Panel will conduct a comprehensive assessment of the risk posed by this bacteria Xylella fastidiosa to the EU crops and plants.
The introduction and spread of plant pests, such as fungi, bacteria, viruses and insects, among food crops is a serious threat that can have far-reaching economic, social and environmental consequences. Plant pests are often introduced to areas previously unaffected through plant imports.
In Europe, protective measures against the introduction of new plant pests are based on regulatory controls on the movement of plants and plant products. The evaluation of the probability of plant pests being introduced and then spreading in an area and the assessment of the potential consequences help inform the decision making on protective measures. The key tasks of EFSA’s Plant Health (PLH) Panel are to assess the risk of exotic plant pests (from non EU countries) using a wide-range of specialist expertise and the most current scientific knowledge available in order to provide scientific advice to the European Commission.
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EPPO Gallery. Symptoms of quick decline (complesso del disseccamento rapido dell’olivo) observed in Puglia (IT) on olive trees. Xylella fastidiosa, Phaeoacremonium spp., Phaemoniella spp., and Zeuzera pyrina have been found in association with this disease.
*Courtesy: Donato Boscia, Istituto di Virologia Vegetale del CNR, UOS, Bari (IT) - Franco Nigro, Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi di Bari (IT) - Antonio Guario, Plant Protection Service, Regione Puglia (IT)