The generalization of the use of pesticides in pest management programmes has led to the emergence and rapid evolution of resistance in pest populations, threatening crop yield and quality and rendering long-term control difficult. Bemisia tabaci (Gennadius) is a major pest distributed worldwide and composed of more than thirty cryptic species. Three whitefly species coexist in La Rèunion, an island in the southwest Indian Ocean, two of which are widespread. The indigenous IO species and the invasive MEAM1 species, can be found preferentially on weeds and crops, respectively. In other countries, MEAM1 has already demonstrated high resistance levels to all of the important classes of insecticides commonly used to control those populations. To assess the resistance status of these two species in La Rèunion, fifteen populations were collected all over the island from greenhouses, open fields, borders of cultivated sites and from natural areas. Three main classes of pesticides were tested in leaf-dip bioassays using formulated acetamiprid (Supreme 20 SG, 200 g.kg-1), pymetrozine (Plenum 50 WG, 500 g.kg-1) and deltamethrin (Decis Protech, 15 g.L-1), which belongs to Neonicotinoid, Pyridine azomethine derivatives and Pyrethroid, respectively. The resistance ratios (RRs) of the sampled populations were calculated relative to a known susceptible laboratory strain. The susceptibility to acetamiprid varied among the collected MEAM1 populations (RRs: 3,3-147). The MEAM1 species displays evidence of high resistance to both deltamethrin (LC50 > 3,25 ml.L-1) and pymetrozine (LC50 > 10000 mg.L- 1). Differences in LC50 observed between MEAM1 and IO laboratory strains were less than 3-fold for both pymetrozine and acetamiprid, but more than 550-fold for deltamethrin meaning that this IO population is more susceptible to this pyrethroid. Our results are in line with loss of efficacy reported in the field for acetamiprid and pymetrozine. Moreover, it echoes the distribution of IO and