Browsing by Author "Rose, H.A."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Biochemical mechanisms of insecticide resistance in the diamondback moth (DBM), Plutella xylostella L. (Lepidopterata: Yponomeutidae), in the Sydney region, Australia(Australian Journal of Entomology, 2009-11) Eziah, V.Y.; Rose, H.A.; Wilkes, M.; Clift, A.D.Following the detection of resistant diamondback moth (DBM) populations to synthetic pyrethroid, organophosphorus and indoxacarb insecticides in the Sydney Basin, a study of the major biochemical mechanisms was conducted to determine the type of resistance in these populations. The activity of cytochrome P450 monooxygenases increased two- to sixfold when compared with the susceptible strain. Up to a 1.9-fold increase in esterase activity in resistant strains compared with the susceptible strain was observed. In vitro inhibition studies showed that profenofos, methamidophos and chlorpyrifos strongly inhibited the esterases while permethrin and esfenvalerate resulted in less than 30% inhibition. Qualitative analysis of the esterases using native polyacrylamide gel electrophoresis showed four bands in both the susceptible and resistant individuals with more intense staining in the resistant individuals. The development of these bands was inhibited by methamidophos and chlorpyrifos pretreatment of the protein extract while permethrin and esfenvalerate did not exhibit this effect. Glutathione S-transferase (GST) activity was significantly higher in two field populations compared with the remaining populations. Overall, the study showed that the mechanisms of insecticide resistance in the DBM populations in the area studied were due to cytochrome P450 monooxygenases, esterase and GSTs, and possibly other non-metabolic mechanisms that were not investigated in the present study. © 2009 Australian Entomological Society.Item Susceptibility of four field populations of the diamondback moth Plutella xylostella L. (Lepidoptera: Yponomeutidae) to six insecticides in the Sydney region, New South Wales, Australia(Australian Journal of Entomology, 2008-10) Eziah, V.Y.; Rose, H.A.; Clift, A.D.; Mansfield, S.Concerns about the failure of insecticides to control the diamondback moth (DBM) Plutella xylostella in the Sydney region of New South Wales, Australia, necessitated the current investigation to establish the susceptibility of four field populations of the DBM to six insecticides. These include two each of organophosphates (OPs), and synthetic pyrethroid insecticides as well as two new products with different modes of action, spinosad and indoxacarb, currently recommended for DBM control in the region. Topical application of the insecticides to the third-instar larvae showed high resistance to pyrethroids (permethrin and esfenvalerate) of 35.0- to 490.0-fold. Resistance to the OPs (methamidophos and chlorpyrifos) and indoxacarb ranged from 12.1- to 36.2-fold and from 11.4- to 34.6-fold, respectively. However, the field populations were susceptible to spinosad (resistance factors only two- to threefold compared with the susceptible strain). A 2 h pre-treatment of the esfenvalerate-resistant strain with the synergists piperonyl butoxide and diethyl maleate increased the toxicity of esfenvalerate by 30.0- and 1.9-fold, respectively, suggesting the involvement of esterases and/or monooxygenases as the key mechanism(s) of insecticide resistance with glutathione S-transferases playing a minor role. © 2008 The Authors.