Resistance to pyrethroids

In some resistant strains, both types of resistance mechanism have been shown to operate against the same insecticide. Thus, the PEG87 strain of the tobacco bud worm (Heliothis virescens) is resistant to pyrethroids on account of both a highly active form of cytochrome P450 and an insensitive form of the sodium channel (Table 4.3 and McCaffery 1998). 

McCaffery, A.R., GladweU, R.T., and El-Nayir, H. et al. (1991). Mechanisms of resistance to pyrethroids in laboratory and field strains of Heliothis virescens. Southwestern Entomologist Supplement 15, 143-158. 

Sawicki, R.M. 1985. Resistance to pyrethroid insecticides in arthropods. Pages 143-192 in D.H. Hutson and T.R. Roberts (eds.). Progress in Pesticide Biochemistry and Toxicology. Vol. 5. Insecticides. John Wiley, New York. 

Cross-resistance to pyrethroids for outdoor use has developed markedly in M. domestica, mosquitoes, cockroaches, and so on however, it has also been found that natural pyrethrins as well as d-allethrin and prallethrin (ETOC ), which have very similar chemical structures and the same configuration as natural pyrethrins, show an extremely low degree of cross-resistance development by these highly-resis-tant sanitary pests compared to photostable pyrethroids. Many novel synthetic pyrethroids recently developed as household insecticides have tended to pursue efficacy improvements in terms of rapid knock-down effects, residual efficacy or volatility. 

Resistance genes can be dominant, recessive, incompletely dominant, or incompletely recessive. Resistance to carbamates and organophosphates is usually dominant or incompletely dominant. Resistance to DDT, Bt, and spinosyns is usually recessive. Resistance to dieldrin is usually incompletely dominant. Resistance to pyrethroids is usually incompletely recessive. As shown in Figure 10.1 and 10.2, diamondback moth resistance to per-methrin was inherited as an incompletely recessive, autosomal factor, whereas resistance to methomyl was inherited as an incompletely dominant, autosomal factor. In cases of monofactorial inheritance of resistance to insecticides, the degree of dominance (D) in the progeny can be calculated, as described by Stone (1968), as follows ... 

Roditakis, E., Tsagkarakou, A., and Vontas, J., Identification of mutations in the para sodium channel of Bemisia tabaci from Crete, associated with resistance to pyrethroids, Pestic. Biochem. Physiol., 85,161, 2006. 

Soderlund, D.M. and Knipple, D.C., The molecular biology of knockdown resistance to pyrethroid insecticides, Insect Biochem. Molec. Biol., 33,563, 2003. 

Naturally Occurring Point Mutations in the Sodium Channel Gene Responsible for Knockdown Resistance to Pyrethroids. 

Several point mutations in the sodium channel gene are associated with kdr and kdr-type resistance to pyrethroids in agriculturally or medically important arthropod species. The most common mutation is the leucine (L) to phenylalanine (F) or histidine (H) or serine... 

Glynne-Jones, G.D. (1983). The use of piperoryl butoxide to increase susceptibility of Insects which have become resistant to pyrethroids and other insecticides, im. Pest Com rot 15, 14-15. 21. 

Molecular Genetic Approach to the Study of Target-Site Resistance to Pyrethroids and DDT in Insects... 

A case in point is the unraveling of resistance to methyl parathion in the tobacco budworm, Heliothis virescens, which is a major pest of cotton as well as tobacco. In South Carolina, there is very severe, stable resistance. Although pyrethroid insecticides are very effective and there is no resistance to them in South Carolina at this time, it would be very useful to understand the genetic basis of methyl parathion resistance in case resistance to pyrethroids should arise in the future or spread eastward from Texas where it has been detected. Recent investigations with this pest will be described to illustrate certain mechanisms. 

Clearly the tobacco budworm is a highly adaptable species that possesses an impressive arsenal of natural physiological and biochemical defense mechanisms which can be brought to bear against a broad spectrum of xenobiotic compounds. Furthermore, recent laboratory studies have shown that the genetic traits of the pest also favor the development of significant levels of resistance to pyrethroids (36.371 when it is subjected to selection pressure. 

It is well established that the modes of action of DDT and pyrethroids are somewhat alike, and that genes for resistance to DDT also confer cross-resistance/tolerance to pyrethroids in a number of arthropod species (25). This probably is true for the tobacco budworm as well. With its past history of DDT resistance and the likelihood that genes for resistance to DDT still exist within the population, the tobacco budworm would be expected to have a head start in developing resistance to pyrethroids. It is interesting that H. zea. which also demonstrated high levels of DDT resistance... 

With a few notable exceptions all key pests are effectively controlled with pyrethroids. The extent to which economically important insects develop resistance to pyrethroids will profoundly influence their future application. The restricted use of photolabile pyrethroids mainly against medical and domestic pests resulted in low level of resistance, but the recent widespread application of photostable pyrethroids has exposed in some insects the potential to develop very strong resistance (Briggs et al., 1984). 

In this article, the level of susceptibility to various insecticides in different human head louse populations in the US was investigated to assess the distribution of resistance. We also reported on the molecular mechanisms of head louse resistance to pyrethroid mediated by sodium channel mutations. Also discussed were the genotyping techniques for resistance monitoring and the... 

Molecular Mechanisms of Head Louse Resistance to Pyrethroids and Development of Monitoring Tools for Resistance Management... 

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