In vitro effectiveness of ivermectin and spinosad flystrike treatments against larvae of the Australian sheep blowfly Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae)
Article first published online: 29 OCT 2008
© 2008 The Authors. Journal compilation © 2008 Australian Entomological Society
Australian Journal of Entomology
Volume 47, Issue 4, pages 365–369, November 2008
How to Cite
Levot, G. and Sales, N. (2008), In vitro effectiveness of ivermectin and spinosad flystrike treatments against larvae of the Australian sheep blowfly Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae). Australian Journal of Entomology, 47: 365–369. doi: 10.1111/j.1440-6055.2008.00670.x
- Issue published online: 29 OCT 2008
- Article first published online: 29 OCT 2008
- Accepted for publication 19 April 2008.
- Lucilia cuprina;
Compared with the reference susceptible strain neonate larvae of composite field strains of the Australian sheep blowfly, Lucilia cuprina displaying either moderate diazinon and diflubenzuron resistance or, moderate diazinon and extreme diflubenzuron resistance, were equally cross-resistant to ivermectin and spinosad. Resistance factors were low (2–3×). As third instar larvae these strains exhibited cross-resistance to ivermectin by better tolerating exposure to higher concentrations, or longer exposure to the registered concentration (32 mg/L). Despite this, larval mortality in each strain exceeded 85% following exposure to ivermectin at the registered flystrike dressing concentration for as little as 30 s. As third instar larvae these strains and the reference strain, were equally susceptible to spinosad, but mortality was only around 40% even after immersion for 60 s in an aqueous solution at the registered rate (25 mg/L). Maximum mortality (99%) was observed in larvae immersed in 250 mg/L spinosad. Two hours after 30 s immersion in ivermectin (32 mg/L) 80% of third instar larvae were no longer moving. This figure rose to 99% by 6 h. In similar bioassays spinosad (25 mg/L) failed to elicit obvious symptoms within 10 h of treatment.