Pesticide Resistance Strategies and Tactics for Management (1986) / Chapter Skim
Currently Skimming:
Experimental Population Genetics and Ecological Studies of Pesticide Resistance in Insects and Mites
Experimental Population Genetics and Ecological Studies of Pesticide Resistance in Insects and Mites
Pages 257-270
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 257... ...
Important parameters for further research include initial allele frequencies and immigration rates. INTRODUCTION One objective of population genetics is to describe evolutionary change.
|
From page 258... ...
Despite these difficulties initial resistance allele frequencies could and should be measured. Some resistance management strategies depend on allele frequency.
|
From page 259... ...
Conversely, a dose that would kill susceptible homozygotes but not the heterozygotes makes resistance functionally dominant, since heterozygotes and RR homozygotes are phenotypically similar. This concept of adjusting the dose is often called alteration of dominance, but could be called alteration of relative fitness.
|
From page 260... ...
RELATIVE FITNESSES Untreated Habitats Resistant genotypes must be at a reproductive disadvantage in the absence of pesticides. If not, resistance alleles would be more common prior to selection (Crow, 1957~.
|
From page 262... ...
Thus, at resistance allele frequencies of 20 percent, for example, 32 percent of the population will carry RS, and only 4 percent will carry RR. Clearly resistance management will be best served by comparisons of RR, RS, and SS genotypes in similar genetic backgrounds.
|
From page 263... ...
depends on an implicit assumption about Ro. For logistical reasons population cages must be maintained at a relatively constant density, so Ro is about 1, which is probably closer to field conditions than if Ro is around 50.
|
From page 264... ...
Therefore, laboratory results may be realistic if the laboratory conditions simulate the field as much as possible. The most realistic studies of this kind may be conducted on species whose behavior and ecology are not too disrupted by laboratory or greenhouse settings, including Musca domestica, Tetranychus urticae, Blatella germanica, and Tribolium castaneum.
|
From page 265... ...
reported on a population-cage study of diazinon resistance in sheep blow flies. The frequency of resistance phenotypes declined quickly from an initial frequency of about 90 percent, then slowed dramatically (White and White, 1981)
|
From page 266... ...
The frequency of the diazinon-resistance allele appears to be about 0.27 in Mississippi house flies (Whitehead et al., 19851. The resistance allele in the sheep blow fly was maintained in very high frequency by continuous diazinon use against the insect for more than 10 years, which is rather unusual (McKenzie et al., 19821.
|
From page 267... ...
As was true for initial R allele frequencies, and in contrast to factors like refugia, current estimates of immigration rates vary over several orders of magnitude. This emphasizes not only the need to tailor resistance management programs to individual species but also the need to improve estimates of immigration.
|
From page 268... ...
1976. The genetic basis for organophosphorous resistance in the Australian sheep blowfly, Lucilia cuprina (Wiedemann)
|
From page 269... ...
1982. The effect of genetic background on the fitness of diazinon resistance genotypes of the Australian sheep blowfly, Lucilia cuprina.
|
From page 270... ...
1980. Field studies on insecticide resistance in the Australian sheep blowfly, Lucilia cuprina.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.