Cartap resistance and synergism in populations of Tuta absoluta (Lep., Gelechiidae)

Control failures of cartap when used against the tomato leafminer Tuta abso luta (Meyrick) in Brazil and a recent report of cartap resistance in Brazil ian populations of this pest species led to the investigation of the possib le involvement of detoxification enzymes on this phenomenon using insectici de synergists. The insect populations were collected from seven different s ites in the states of Minas Gerais, Rio de Janeiro and Sao Paulo. These pop ulations were subjected to insecticide-impregnated filter paper assays. The concentration-mortality assays were carried out for cartap alone and in a mixture (1 cartap:10 synergist) with the synergists diethyl maleate, pipero nyl butoxide and triphenylphosphate which, respectively, inhibit the enzyme s glutathion-S-transferases, cytochrome P450-dependent monooxygenases and e sterases. Resistance to cartap was observed in all populations when compare d with the standard susceptible population, with resistance ratios ranging from 2.3- to 21.9-fold. Piperonyl butoxide was the most efficient synergist with cartap synergism ratios ranging from 1.3- to 21.0-fold and nearly com pletely suppressing the resistance to cartap in all of the populations stud ied, suggesting a major involvement of cytochrome P450-dependent monooxygen ases as a cartap resistance mechanism in these populations of T. absoluta. Diethyl maleate and triphenylphosphate also synergized cartap in nearly eve ry population, and they still provided partial suppression of cartap resist ance in the leafminer populations studied. Therefore, glutathion-S-transfer ases and esterases seem to play a secondary role in cartap resistance in Br azilian populations of T. absoluta.