Stepping up surveillance of the oriental fruit fly to prevent it from becoming established in France
Bactrocera dorsalis, commonly known as the oriental fruit fly, is one of the most destructive pests for many fruit and vegetable production sectors. In its opinion, ANSES considers that the likelihood of its long-term establishment in mainland France is not negligible. To be able to detect any outbreak of infestation as quickly as possible, ANSES recommends stepping up the surveillance of crops and imported goods in Mediterranean areas near ports and airports, beyond what is provided for in the current regulations.
A threat to many fruit and vegetable crops
Native to Asia, Bactrocera dorsalis is now found in a large part of sub-Saharan Africa, as well as on the Indian sub-continent towards China, throughout South-East Asia, and on several Pacific islands. The oriental fruit fly can feed on a wide variety of fruit and vegetables, including mangoes, citrus fruits, peaches, plums, apricots, grapes, avocados and tomatoes. More than 500 species of host plants have been identified in all. The female lays her eggs under the skin of the fruit, and the resulting larvae then feed on the pulp, causing the flesh of the fruit to deteriorate or even be completely destroyed. The larvae then burrow into the soil beneath the plant to turn into pupae, from which the adult flies emerge.
B. dorsalis is one of the 20 quarantine pests classified as priority pests for the European Union. Despite the regulations already in place aimed at preventing this species from entering Europe, several outbreaks have been reported in Italy. In France, B. dorsalis is covered by a National Emergency Health Response Plan (PNISU), which consists in implementing control measures in the event of an outbreak, such as insecticide treatments, the trapping of males to limit their reproduction, and restrictions on movements of plant material.
To date, no outbreaks of B. dorsalis have been reported in mainland France. Nevertheless, the number of flies caught by traps installed as part of official surveillance efforts has increased in recent years. These flies are often caught near ports, airports, and wholesale markets selling fresh produce.
High likelihood of the oriental fruit fly entering France
According to the expert appraisal carried out by ANSES, the oriental fruit fly is most likely to enter France through fruit and vegetables commercially imported from infested countries. These fruit and vegetables have been classified according to the volume of imports from infested countries, their ability to carry the fly’s larvae, and data from interceptions of flies on fruit and vegetables at French border control posts. Mangoes, passion fruit, avocados and guavas pose a high risk, and the fly has already been intercepted on them.
Moreover, the Agency points out that the risk associated with fruit carried by passengers, particularly those travelling by air, should not be overlooked, especially as this type of good is not packaged or controlled for export.
Imposing tighter controls on imported fruit and vegetables to prevent entry
The Agency recommends stepping up inspections for the highest-risk goods, such as passion fruit and avocados, especially when they are not covered by mandatory checks under the current regulations. The Agency also reiterates the need to strictly comply with the applicable requirements for fruit such as mangoes imported from countries infested with B. dorsalis, to ensure the quality of goods.
The Agency adds that it is important to make travellers aware of the risks involved in moving plants and plant products. It supports a strict ban on passengers importing plants that could provide a pathway of entry for pests such as B. dorsalis.
Moderate likelihood of long-term establishment in the low-lying Mediterranean belt, including Corsica
The likelihood of B. dorsalis becoming established in mainland France depends mainly on the abundance of plant host species for B. dorsalis, and particularly on fruit production in départements located in Mediterranean regions (PACA, Occitanie and Corsica) and in Nouvelle-Aquitaine. In terms of climate, the low-lying Mediterranean belt, including Corsica, is the only area that may potentially be favourable for the long-term establishment of B. dorsalis in France.
“This species of fly is highly polyphagous, meaning it can feed on a wide variety of plants. What’s more, climate modelling points to potentially favourable conditions for its establishment in the low-lying Mediterranean belt, which includes Corsica. There is no shortage of host plants in this area, including citrus fruits in winter, which would enable the fly to feed all year round” explains Christine Tayeh.
Therefore, to increase the chances of detecting the entry of the fly and eradicating any outbreak in a favourable area, the Agency recommends stepping up surveillance, including trapping among crops in the vicinity of border control posts in Mediterranean regions and including plants such as fig trees that are not currently targeted by surveillance efforts.