ARS | Publication request: Variation of acephate susceptibility and correlation with Esterase and Glutathione S-transferase activities in field populations of the tarnished plant bug, Lygus lineolaris

Submitted to: Journal of Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2012
Publication Date: May 23, 2012
Repository URL: http://handle.nal.usda.gov/10113/54362
Citation: Zhu, Y., Luttrell, R.G. 2012. Variation of acephate susceptibility and correlation with Esterase and Glutathione S-transferase activities in field populations of the tarnished plant bug, Lygus lineolaris. Journal of Pesticide Biochemistry and Physiology. 103:202-209. http://www.sciencedirect.com/science/article/pii/S0048357512000673

Interpretive Summary: The tarnished plant bug (TPB) has become a more economically important pest of cotton in recent years. Heavy dependence on insecticides, particularly organophosphates and pyrethroids, for TPB control facilitated resistance development to multiple classes of insecticides. To better monitor resistance in field populations, this study examined acephate susceptibility and major detoxification enzyme activities in 9 field populations collected in the Delta region of Mississippi and Arkansas. Two Arkansas populations in Reed and Backgate have developed 3.5- and 4.3-fold resistance to acephate. A 2.2-fold resistance, detected in a field population from Lula, Mississippi, was elevated to 5.9-fold after a selection with 600 mg/L acephate. Reduced susceptibility to acephate was highly correlated with elevated esterase activities. The acephate-resistant populations from Backgate, Lula, and Reed consistently had higher (up to 5.3-fold) esterase activities than susceptible populations. Regression analysis of dose mortality rate with esterase activities revealed a significant polynomial quadratic relationship with relative regression up to 0.89. Glutathione S-transferase (GST), another resistance-related enzyme, also had elevated activity in most populations, except for the Lula population whose GST activity was relatively lower than the susceptible strain. Finally, examination of esterase and GST inhibitors indicated that suppression rates (up to 70%) by two esterase inhibitors in 2010 were slightly lower than those detected in 2006, while ethacrynic acid (EA) exhibited effective GST inhibition years. Two other GST inhibitors (BSP and DEM) displayed significantly lower suppression rates in 2010 than those detected in 2006, suggesting a necessity of continued monitoring for insecticide resistance using both bioassay and biochemical approaches. This study provided an insight of acphate resistance status in field populations with both biological dose response and mechanistic details.

Technical Abstract: The tarnished plant bug (TPB) has increasingly become an economically important pest of cotton. Heavy dependence on insecticides, particularly organophosphates and pyrethroids, for TPB control facilitated resistance development to multiple classes of insecticides. To better understand resistance and explore ways to monitor resistance in field populations, this study examined acephate susceptibility and major detoxification enzyme activities in nine field populations collected in the Delta region of Mississippi and Arkansas. Two Arkansas populations from Reed and Backgate had 3.5- and 4.3-fold resistance to acephate, as compared to a susceptible laboratory strain. A 2.2-fold resistance, detected in a field population from Lula, Mississippi, was elevated to 5.9-fold after a selection with 600 mg/L acephate. Reduced susceptibility to acephate was highly correlated with elevated esterase activities. The acephate-resistant populations from Backgate, Lula, and Reed consistently had higher (up to 5.3-fold) esterase activities than susceptible populations. Regression analysis of LC50s with kinetic esterase activities revealed a significant polynomial quadratic relationship with R2 up to 0.89. Glutathione S-transferase (GST), another resistance-related enzyme, also had elevated activity in most populations, except for the Lula population whose GST activity was relatively lower than the susceptible strain. Finally, examination of esterase and GST inhibitors indicated that suppression rates (up to 70%) by two esterase inhibitors in 2010 were slightly lower than those detected in 2006, while ethacrynic acid (EA) exhibited effective GST inhibition years. Two other GST inhibitors (BSP and DEM) displayed significantly lower suppression rates in 2010 than those detected in 2006, suggesting a necessity of continued monitoring for insecticide resistance with both bioassay and biochemical approaches. This study provided insight into acphate resistance status in field populations of TPB with both biological dose response and mechanistic details.