Cross resistance spectra and effects of synergists in insecticide-resistant strains of Lucilia cuprina (Diptera: Calliphoridae)

Abstract

Cross-resistance spectra were determined in strains of the Australian sheep blowfly, Lucilia cuprina (Wiedemann), which had been pressured for several years in the laboratory with diflubenzuron, butacarb or deltamethrin. Each strain was highly resistant to its selecting chemical (resistance factors > 1000-fold), however, cross-resistance levels were variable and often low. In particular, strains selected with diflubenzuron and butacarb showed very little resistance to deltamethrin (resistance factors < 7-fold). Each strain showed resistance levels to diazinon only slightly higher than the highest levels currently detected in field strain larvae. Piperonyl butoxide and triphenyl phosphate significantly synergized each pressured strain with its selecting chemical, suggesting the involvement of both monooxygenases and esterases in the observed resistances. Synergism ratios in each case were greater with piperonyl butoxide. The lack of any alteration in in vitro acetylcholinesterase sensitivity to butacarb inhibition in the butacarb-selected strain, and only low level resistance to DDT in the deltamethrin-selected strain, provided no evidence for target-site insensitivities in these strains. The low-moderate levels of cross-resistance therefore imply the existence of qualitative differences in the detoxification systems in each strain.

Insect growth regulator cross‐resistance studies in field‐ and laboratory‐selected strains of the Australian sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae)

“…Prior to, and since its registration for use on sheep, we have used sequential pressuring of field-derived larvae with diflubenzuron to create a highly resistant strain (DFB-sel). This strain is also resistant to organophosphate and carbamate insecticides (Kotze & Sales 1994).…”

Inheritance of Diflubenzuron Resistance and Monooxygenase Activities in a Laboratory-Selected Strain of <I>Lucilia cuprina</I> (Diptera: Calliphoridae)

“…These results indicate that the Dfbsel strain adheres to the general pattern described by McKenzie and Batterham (1994) for laboratory-selected polygenic resistance. Earlier studies demonstrated enhanced monooxygenase activities in the Dfbsel strain relative to the LS strain (Kotze 1993) and signiÞcant synergism of dißubenzuron by piperonyl butoxide with Dfbsel larvae (Kotze and Sales 1994), suggesting a role for cytochrome P450 enzymes in the resistance. The current study has demonstrated parallels between inheritance of dißubenzuron resistance and monooxygenase activities.…”

“…While the Dfbsel strain shows no increase in general esterase activity in vitro relative to a laboratory susceptible strain (A.C.K., unpublished data), a low level of synergism by triphenyl phosphate suggests a role for esterase enzymes in the resistance (Kotze and Sales 1994). The current study was, therefore, initiated to further deÞne the nature of the resistance shown by the Dfbsel strain by examining its inheritance in matings with a susceptible strain.…”

“…To study the potential for dißubenzuron resistance to develop in this species, a resistant strain (Dfbsel) has been generated in the laboratory by exposure of larvae to the compound at each generation over several years (Kotze and Sales 1994). Enhanced monooxygenase enzyme levels and signiÞcant synergism by piperonyl butoxide suggest a role for cytochrome P450-mediated metabolism in the high level resistance shown by this strain (Kotze 1993, Kotze andSales 1994).…”

Thein vitroresponse of field strains of sheep blowfliesLucilia sericataandL. cuprina(Calliphoridae) in New Zealand to dicyclanil and triflumuron

“…Later, some populations of L. cuprina in both Australia and New Zealand showed reduced susceptibility to a new active ingredient in dips, the benzoyl ureas, and L. sericata demonstrated more widespread organophosphate resistance than previously (Kotze et al 1997;Haack et al 1999;Wilson 1999). Weak side-resistance to other organophosphates was detectable and the degree of resistance to diflubenzuron, a benzoyl urea, was positively correlated with diazinon resistance (Kotze and Sales 1994;Haack et al 1999).…”