Parathion resistance mechanisms

Lewis, J.B. and Sawicki, R.M., Characterization of the resistance mechanisms to diazinon, parathion and diazoxon in the organophosphorus-resistant SKA strain of house flies (Musca domestica L.), Pestic. Biochem. Physiol., 1, 275,1971. 

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. 

Can individual alleles for resistance be detected in the field This will be necessary in order to develop sound resistance management strategies. An example of the complexity of the problem is analysis of methyl parathion resistance, in which we have preliminary evidence for six possible mechanisms in tobacco budworm (Table V). Many important pests have multiple mechanisms toward each group of insecticides. Some are accumulating multiple resistance at an alarming rate. 

Table V. Putative Mechanisms of Methyl Parathion Resistance in Several Strains of the Tobacco Budworm, Heliothis virescens...

Figure 9.2 Devonshire and Sawicki (1979) at Rothamstead Experimental Station, Hertfordshire, U.K., found seven variants of the aphid Myzus persicae with different resistances to parathion. Excess production of a carboxylesterase as a result of one or several gene duplications was found to be the resistance mechanism. High levels of carboxylesterases take paraoxon away from acetylcholinesterase so that aphids become resistant.

Figure 2. Detoxicative mechanisms imparting organo-phosphorus-resistance (e.g. to methyl parathion)...

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