BACKGROUND: The polyphagous cotton-melon aphid Aphis gossypii Glover is structured into geographically widespread host races comprising a few clones specialised on Cucurbitaceae, cotton, eggplant or pepper. To assess insecticide resistance among andwithin host races, leaf disc bioassays were conducted on aphid clones collected from Cucurbitaceae (genotypes C4 and C9), cotton (genotypes Burk and Ivo), eggplant (genotype Auber) and pepper (genotype PsP4). Molecular diagnostic (PCR-RFLP) and enzyme assays were also performed to detect the basicmechanisms underlying insecticide resistance. RESULTS: All six clones were susceptible to acetamiprid (neonicotinoid) or carbosulfan (carbamate). Conversely, all clones were resistant to dimethoate (organophosphate) (RF = 4.1-38.1) and carried mutation S431F in the acetylcholinesterase gene. Auber, PsP4 and Burk also carried mutation A302S in this gene,which possibly conferredmoderate resistance (RF= 3.7-6.8) to profenofos andmonocrotophos (organophosphates). Auber and Burk were highly resistant (RF= 41.2 and 473 respectively) to cypermethrin (pyrethroid). This resistance was likely associated with point mutation super-kdr (M918L) in the voltage-gated sodium channel gene (para gene) ormetabolic detoxificationmediated by esterase and oxidase enzymes. CONCLUSION:Multiple resistance to a broad range of insecticides andmultiplemechanisms of resistance in some clones could explain to some extent the low genetic diversity observed within A. gossypii host races.