Negative cross-insensitivity in insecticide-resistant cotton aphid Aphis gossypii glover

The cotton aphid, Aphis gossypii G., is a widespread agricultural pest and many populations around the world display resistance to pirimicarb. This re sistance originates mainly from acetylcholinesterase modification. Hydrolys is of 14 carbamate and organophosphate insecticides by altered acetylcholin esterase of a resistant strain from southern France has been analyzed. It a ppeared that the modified enzyme provides a specific resistance to pirimica rb but also a greater sensitivity to bendiocarb. Bioassays showed that the resistant strain was slightly more sensitive to bendiocarb. Utilization of this antiresistance property was tested in the laboratory: a mixed populati on containing 50% pirimicarb-resistant and 50% pirimicarb-susceptible aphid s was established and repetitively treated with bendiocarb. Frequency of re sistant individuals in this population was monitored and compared to that o f a nontreated mixed population. Treatments with bendiocarb delayed the inc rease of resistant individuals but as the resistant strain displayed a high er fitness than the sensitive strain and as antiresistance was weak, this s election assay did not allow the population to revert. These data showed th at application of this strategy in fields requires compounds displaying hig h antiresistance properties. (C) 1999 Academic Press.