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

Abstract

Resistance to diflubenzuron in the Australian sheep blowfly, Lucilia cuprina , has rendered this insecticide incapable of preventing flystrike in sheep from a few districts in eastern Australia. Wool producers affected by this situation must find suitable alternatives to protect their flocks. Results of laboratory bioassays against one population demonstrated that, despite extremely high diflubenzuron resistance (Resistance Factor > 791), it had only very low (2x) tolerance of cyromazine and dicyclanil. It is unlikely that this level of tolerance would have any practical impact on field control with either insecticide. Consequently, wool producers in districts where diflubenzuron-resistant flies are common can rotate insecticide treatment to either of these compounds to prevent flystrike in their flocks. However, unlike the highly diflubenzuron-resistant field strain, a laboratory strain selected for resistance to diflubenzuron (Resistance Factor = 617) was 10 times more resistant to dicyclanil than a susceptible strain but, like the field strain, was only two times more tolerant of cyromazine. Conversely, a field-derived strain selected in the laboratory for cyromazine resistance was 20 times more resistant to dicyclanil and 362 times more resistant to diflubenzuron than the reference susceptible strain.

Larvicidal activity of camphor and lavender oils against sheep blowfly, Lucilia sericata (Diptera: Calliphoridae)

“…Blowfly control is important, and has relied on the use of organophosphate and synthetic pyrethroid dips and sprays (French et al 1994;Tellam and Bowles 1997) as well as insect growth regulators (French et al 1994;Levot and Sales 2004). Prior to development and commercial success of synthetic insecticides in mid-1930s to 1950s, botanical insecticides were the foremost weapons against insect pests.…”

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

“…The steepness of probit lines (i.e. the slope) reflects the homogeneity of the response to the actives in most populations (Levot and Sales 2004) whereas the W2 strain exhibits heterogeneity of response to triflumuron suggesting there are more alleles potentially subject to selection pressure from insecticides. Of interest is that the next level of resistance (RF45) was shown by strains from populations of L. cuprina from East Coast, Tararua and Wairarapa, with 1 (the highest RF at 16) from Canterbury in the South Island.…”

“…All assays were conducted using technical-grade chemicals; triflumuron 98.4% and dicyclanil 99.4% active ingredient (supplied by Novartis New Zealand Ltd, Auckland, NZ) and based on the method described by Levot and Sales (2004), with the exception that the diluents used differed; acetone was used for triflumuron and methanol for dicyclanil. Concentrated stock solutions were made for each chemical; 25 mg/mL for triflumuron and 2.5 mg/mL for dicyclanil.…”

“…Larvae from subsequent generations were used to develop a test protocol based around the methods of Broce and Gonzaga (1987) and Levot and Sales (2004) and to determine suitable dose rates for the chemicals under test. Results from these tests have been included for comparative purposes.…”

“…This is a broad descriptor for any chemical which disrupts the developmental process of insects at a defined point or points, and there are a number of chemical groups that are able to achieve this with differing modes of action. The first IGR cyromazine (a triazine), was registered in 1979 and diflubenzuron, a benzoyl urea, around 1994 in Australia (Levot and Sales 2004), both providing longer protection against flystrike than the failing diazinon. More recently another benzoyl urea, triflumuron and a pyrimidine carbonitrile, dicyclanil (the latter registered in 1999) were made available as dip formulations to sheep farmers in New Zealand.…”