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A virus threatening courgettes detected for the first time in France

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News of 27/10/2020

The Tomato leaf curl New Delhi virus (ToLCNDV) is a virus that can spread rapidly in courgette crops, causing considerable damage. ANSES’s Plant Health Laboratory confirmed its presence in France, although the country had been disease-free prior to that time. 

Described for the first time in India in tomato plants, the ToLCNDV virus is currently found in several European Countries (Spain, Portugal, Italy, Greece and Estonia), where it causes damage to courgette, cucumber and melon crops. Sighted in France by sector professionals, the presence of ToLCNDV has just been confirmed following analyses by ANSES in four courgette production areas, in the Occitanie and Provence-Alpes-Côte-d'Azur regions.

Spread worsened by the presence of a highly efficient vector

The virus, belonging to the Geminiviridae family, is transmitted mainly by the Bemisia tabaci whitefly, an insect vector considered to be highly effective in spreading the disease. This insect vector acquires the virus within 15 to 30 minutes when it draws sap from infected plants.  It then retains the virus for life and can spread it for several days by infecting healthy plants. 

Considering the situation in the countries where it has been detected, the virus is likely to infect a very large number of plant species such as potatoes, tomatoes, courgettes, aubergines, melons, cucumbers, bell peppers and squash, causing significant damage to crops. It affects courgette plants by stunting their growth and causing chlorosis. The leaves become deformed, curl up and display various degrees of mosaic effects. 

As with all plant viruses, there is no known treatment that can cure an infected plant. To prevent its spread, prevention is therefore essential, and should include the use of healthy plant material or plants, the elimination of diseased plants and control of insect vector populations.

The Plant Health Laboratory, a national reference laboratory 

The ToLCNDV virus is a quarantine pest and is therefore regulated at European level. In France, ANSES’s Plant Health Laboratory carries out official analyses to confirm its presence. A method enabling the identification of viruses of the same family is first used and then, in the case of a positive result, the analysis of the specific genetic sequence of ToLCNDV is needed to finalise the diagnosis. In order to strengthen virus detection capacity, ANSES is also testing several real-time PCR detection methods and is participating in an inter-laboratory trial organised at European level by the European Union Reference Laboratory. 

Not to be confused with tomato brown rugose fruit virus (ToBRFV)

In February 2020, ANSES warned of a new emerging virus that was especially dangerous for tomatoes. This virus, ToBRFV, is transmitted through infected seeds, plants and fruit, as well as by simple contact, and can survive for extended periods without losing its infectious potential. Although it was detected in February 2020 in the region of Brittany, no new outbreaks have since been identified. The measures taken in Europe have led to reinforced surveillance of this virus in France, carried out by State services and their delegates, which has limited its spread.