“We risk a major pandemic”

Currently, this Huanglongbing disease (HLB) is the most dangerous for citrus fruits in the world, according to the International Cooperation Center for Agricultural Research (CIRAD) in France, which coordinated this work published at the end of December.

Since the 2000s, it has destroyed the crops of large producers such as China or the United States, forcing them to use large amounts of antibiotics and pesticides.

Europe, until then, had been spared from this scourge. But a team of researchers has found that a tiny insect observed over five years in Spain and Portugal, the African psyllid Triosa erythrae, was able to transmit the bacterium that causes a severe form of HLB.

Bernard Reynaud underlines that this Asian bacterium, called CLas, is “very damaging, causing very rapid death of trees”. .

A disease that spreads in “Asian” and “African” form

Researchers previously thought that the “Asian” form of the disease could only be transmitted by the Asian psyllid, Diaphorina citri, and that its “African” form could only be carried by the African psyllid, Triosa erytrae. The two insects, in fact, belong to different families.

The CIRAD team, which is part of the European Union PRE-HLB for the fight against the disease, compared the prevalence rates of the two species of psyllids and the CLas bacterium on Reunion Island, the only territory where they coexist.

These experiments were able to demonstrate that the African psyllid is “such an effective vector” for transmitting the Asian bacterium, concludes Bernard Reynaud.

Risk of an epidemic

“If the Asian disease returns (in Europe), we risk a major epidemic”, he warns, knowing that control mechanisms have not been adapted. Especially since the CLas bacterium was recently discovered in Ethiopia and Kenya, the Mediterranean basin is closer than ever.

Therefore, researchers recommend strengthening surveillance to avoid the introduction of contaminated plant material (citrus plants, grafts).