Biomarkers of exposure to chlorpyrifos in adults of Cydia pomonella (Lepidoptera: Torticidae)

PARRA MORALES LB; ALZOGARAY RA; SOLEÑO J; CICHÓN L; GARRIDO S; MONTAGNA CM

Guarapari

Congreso; XIII Congresso Brasileiro de Ecotoxicologia; 2014

Sociedade Brasileira de Ecotoxicologia

At the time of pestcontrol, the physiological state of an insect population might be non-uniform.Therefore, a concentration that is lethal to certain individuals may besublethal to another ones. Thus, a proportion of pest population could behighly stressed by the pesticide and yet survive. However, the stress is ageneral enhancer of mutation rates and might lead to pesticide resistance. Thecodling moth, Cydia pomonella(Lepidoptera: Tortricidae), is the most important pest of fruit trees. The pestmanagement program is intended to neonate larvae and includes organophosphatessuch as chlorpyrifos along with other conventional and selective pesticides. Theprimary target of organophosphates is the enzyme acetylcholinesterase (AChE).These pesticides also inhibit carboxilesterases. There is increasing evidencethat these pesticides generate free radical intermediates leading to thedisturbance of the insect homeostasis. The objective of this study was toevaluate the effects of different concentrations of chlorpyrifos on theactivity of both AChE activity and metabolic enzymes in survivor adults of C. pomonella. One-two days-old moths froma field population were exposed for 24 h to dry residues of chlorpyrifos (1 mLof insecticide dissolved in acetone: 0.0625; 0.25; 1; 3.9; 15.6; 62.5; 250 and 500ppm), or acetone alone for controls, applied to glass cups and their lifts. AChEactivities were assayed in the supernatant of head homogenates. The activitiesof esterases (EST), cytochrome P450 monooxygenases (ECOD), glutathioneS-transferases (GST), catalases (CAT), superoxide dismutases (SOD) and GSH content were evaluated from the supernatant of body homogenates.Differences between control and treated groups were analyzed by ANOVA followed byDunnett test. The concentrations of chlorpyrifos required to inhibit 50% (IC50)of AChE and EST activities were 0.3 ppm and 5.7 ppm; respectively. Means ECODactivities showed a concentration-dependent inhibition. At the two lowestpesticide concentrations, the mean EST activities were higher than the controlone. The mean activities of GST, CAT, SOD and GSH content were unaffected byany of the studied concentrations. Results suggest that EST does not play aprotective role against chlorpyrifos, since they were inhibited at higher concentrationsthan AChE. The ECOD activities were highly inhibited even at the lowestpesticide concentration. The antioxidants system showed non-responseat any of the evaluated concentrations of chlorpyrifos.