Journal of Economic Entomology (1995) 88, 11-20

Charles F. Chilcutt and Bruce E. Tabashnik (1995)
Evolution of pesticide resistance and slope of the concentration-mortality line: Are they related?
Journal of Economic Entomology 88 (1), 11-20
Abstract: Researchers have often assumed that slopes of concentration-mortality lines from pesticide bioassays change predictably as resistance evolves. In particular, many authors have used differences in slope among conspecific populations to make inferences about the progression of resistance and the genetic variation available for further increases in resistance. Such inferences are based on the assumption that slope is steepest in populations that are highly susceptible or highly resistant (i.e., such populations have less genetic variation than heterogeneous populations with intermediate levels of resistance). We tested this hypothesis independently for each of 41 sets of bioassay data of conspecific variation in susceptibility to pesticides obtained from 26 articles published in the Journal of Economic Entomology during the past decade. These data represent 18 species of insects and mites and 25 pesticides. We used polynomial regression and a nonparametric approach to examine the relationship between slope and LC₅₀ for each set of bioassay data. We found that, for most pest and pesticide combinations, slopes of the concentration-mortality lines were not highest in the populations with highest and lowest LC₅₀s. This result suggests that slope was not a good indicator of genetic variation in susceptibility or that genetic variation in susceptibility was not related simply to LC₅₀. The slope of the concentration-mortality line provides information about the phenotypic variation within a population, including genetic and environmental variation. If most of the phenotypic variation is not genetically based, variation in estimates of slope among conspecific populations may be caused primarily by changes in environmental variation and errors of estimation.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Bruce E. Tabashnik, Charles F. Chilcutt

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest
Research topic(s) for beneficials or antagonists:
resistance to pesticides

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Leptinotarsa decemlineata
	Cydia pomonella		U.S.A. (NW)
	Anthonomus grandis		Nicaragua
	Plutella xylostella		Indonesia
	Plutella xylostella		U.S.A. (Hawaii)
	Tetranychus urticae		U.S.A. (NW)
	Musca domestica
	Blattella germanica		U.S.A. (SW)
	Haematobia irritans		U.S.A. (mid N)
	Spodoptera exigua
	Trichoplusia ni		U.S.A. (SW)
	Bemisia tabaci		U.S.A. (SW)
	Bemisia tabaci		U.S.A. (Hawaii)
	Heliothis virescens		U.S.A. (SW)
	Heliothis virescens		Mexico
	Scirtothrips citri		U.S.A. (SW)
	Diatraea saccharalis		U.S.A. (mid S)
	Platynota idaeusalis
	Myzocallis coryli		U.S.A. (NW)
Phytoseiulus persimilis (predator)