Susceptibility to insecticides and activities of glutathione S-transferase and esterase in populations of Lygus lineolaris (Hemiptera: Miridae) in Mississippi.

BACKGROUND: Lygus lineolaris (Palisot de Beauvois) is a serious pest of cotton (Gossypium hirsutum L.) in Mississippi, particularly in the Delta region. This may be due to decreased insecticide susceptibility in that region. Research has revealed populations of L. lineolaris in the Delta region with high levels of insecticide resistance; however, comparisons with populations in the remainder of the state are limited.
RESULTS: Experiments were undertaken to compare the LC50 values and activities of detoxification enzymes of L. lineolaris populations. The results of these studies indicated that the LC50 values were not different between the Delta and Hills regions, but differences were significant between populations within and across regions. Results of the detoxifying enzyme activity assays revealed significantly higher esterase activity in the Delta region when compared with the Hills. Glutathione S-transferase activity was not different between regions, but differences within and across regions were significant.
CONCLUSION: The results indicated that glass-vial assays to determine and compare LC50 values may be less accurate than enzymatic assays for detecting insecticide susceptibility differences. Higher esterase activity is likely a contributing factor to the difficulties with managing L. lineolaris in the Mississippi Delta region.