In urban and peri-urban areas
The population remains scattered. Cities and their surroundings are the expansion areas favored by the tiger mosquito, whose female loves nothing so much as the mini-surfaces of stagnant water where she lays her eggs. In flower pot cups, in outdoor toys or in any corner provided it is humid.
The dynamic of progression owes much to its best helper, man. The insect jumped from continent to continent as a stowaway in the dizzying ballet of transporting people and goods. “It has benefited in particular from the export of used tires. Its rise to power dates back to the 1980s, which coincided with the explosion of trade,” recalls Thierry Baldet.
Its spread in France continues via the main roads. It stops in urban areas and their outskirts in Marseille, Lyon, Toulouse, Bordeaux and Paris. We will not dislodge it any more. “It is subservient to humans there, but you must not believe that it is not adapted to rural areas. In its area of origin, it was found rather outside the cities. This is true today in Brazil as in Reunion. Perhaps it competes with local species in European forests and countryside, but it is not excluded that it spreads there”, continues the researcher.
Forbidden in the land of ice
The fate of France is hardly singular. “It is present in tropical and temperate zones in Asia, Americas, Africa and Europe, in more than 150 countries or territories. In Europe it is reported in more than twenty countries”, is recalled in the presentation of an international congress on the pest which was held in mid-May in Montpellier and which brought together more than 120 researchers and actors from public health.
“His plasticity is remarkable. In Europe, it is able to go into diapause (a life in slow motion, editor’s note) in winter. We find him at the Canadian border and he will go as far as Scandinavia. Its limit is the zero isotherm”, specifies Thierry Baldet. In short, like that of the brown rat a few centuries earlier, the dispersal of the tiger mosquito is a remarkable success story, probably boosted by climatic upheavals.
Like that of the brown rat a few centuries earlier, the dispersal of the tiger mosquito is a remarkable success story
When we know that a fertilized female lays three hundred eggs every three days, we can legitimately wonder about the means of stemming the tide. Research is going well. CIRAD and IRD (1) are working on biocontrol methods in Reunion. They pass through the dispersion in nature of males that have become sterile by irradiation. At CIRAD, we tested the method on a related species, Aedes aegypti, by adding a biocide to the released males. “We obtained an 88% reduction in the populations of mosquitoes of this species in the treated areas. It’s encouraging, but the research time is long”, sighs the researcher.