Evaluation of resistance pattern to fenpyroximate and pyridaben in Tetranychus urticae collected from greenhouses and apple orchards using lethal concentration-slope relationship

Eunho Suh, Sang Hyun Koh, Joon Ho Lee, Key Il Shin, Kijong Cho

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This study aimed to monitor the present and future developments of the resistance of Tetranychus urticae Koch to fenpyroximate and pyridaben, using the relationship of the LC50 and slope of the concentration-mortality line in a probit model, for the provision of reliable resistance management tactics. Tetranychus urticae populations were collected from 16 commercial greenhouses, where various crops were cultivated, as well as from 10 apple orchards throughout Korea. The resistance to fenpyroximate and pyridaben of each population was estimated by calculating the median lethal concentration (LC50), resistance ratio (RR) and slope of the concentration- mortality regression. Most of the greenhouse populations exhibited moderate levels of resistance, whereas the apple orchard populations showed only low levels, indicating that T. urticae populations in greenhouses were more strongly selected than those in apple orchards. Four population groups were established based on either the habitats (greenhouse and apple orchard) or acaricides (fenpyroximate and pyridaben). To test the hypothesis, "the slope is greatest at low and high levels of resistance," the slopes were regressed as a function of the LC50, and fitted to a polynomial regression. The polynomial regression model explained this relationship well for the four population groups (p < 0.05), indicating that the development of resistance toward fenpyroximate or pyridaben was consistent with the gradient. A laboratory selection study agreed with the results from both acaricide field populations. These results suggest that the gradient was a good indicator of the susceptibility of T. urticae to genetic variations, which was related to the LC50. The application of these findings is also discussed in relation to the resistance management of T. urticae.

Original languageEnglish
Pages (from-to)151-165
Number of pages15
JournalExperimental and Applied Acarology
Issue number2-3
Publication statusPublished - 2006 Feb 1



  • Concentration-mortality line
  • Genetic variation
  • METIs
  • Polynomial regression
  • Resistance management
  • Two-spotted spider mites

ASJC Scopus subject areas

  • Ecology
  • Insect Science

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