The alert has been given by researchers: the combined presence of an insect, already present in Europe, and an Asian bacterium devastating for citrus fruits, a “major” risk threatens Mediterranean citrus fruits. This is the “yellow dragon” epidemic, they warn in a study coordinated by the Center for International Cooperation in Agricultural Research for Development (CIRAD) and published in the journal Frontières.
Currently, this Huanglongbing disease (HLB) is the deadliest for citrus fruits in the world, according to the same source. And for good reason, since the 2000s, it has decimated the crops of major producers such as China or the United States, forced to use antibiotics and insecticides on a massive scale.
Europe was, until then, spared from this scourge. But a team of researchers has discovered that a tiny insect observed for five years in Spain and Portugal, the African psyllid Trioza erytreae, was able to transmit the bacterium causing the severe form of HLB.
This Asian bacterium, called CLas, is “the one that does the most damage, causing very rapid death of trees”, underlines Bernard Reynaud, lead author of the study and director of a CIRAD/University of Reunion research unit. , quoted by AFP.
Researchers previously thought that the disease in its “Asian” form could only be transmitted by the Asian psyllid, Diaphorina citri, and that its “African” form could only be carried by the African psyllid, Trioza erytreae. The two insects, in fact, belong to different families.
The CIRAD team, which is part of the European PRE-HLB disease control consortium, therefore compared their transmission rates on Reunion Island, the only territory where the two species of psyllids and the CLas bacterium coexist.
These tests made it possible to demonstrate that the African psyllid “was such an effective vector” for transmitting the Asian bacterium, concludes Bernard Reynaud.
“If the Asian disease returned (to Europe), we would risk a major pandemic”, knowing that the means of control are not suitable, he warns. Especially since the CLas bacterium was recently spotted in Ethiopia and Kenya, closer than ever to the Mediterranean basin.
The researchers therefore recommend strengthening surveillance to avoid the introduction of contaminated plant material (citrus plants, grafts), with control, possible quarantines, and early detection in the event of suspicion.