Work

Cross-resistance patterns in field strains of the sheep blowfly following laboratory-based selection pressure with dicyclanil or imidacloprid

Year: 2024

Type: article

Abstract: Control of the sheep blowfly relies largely on the use of insecticides applied prophylactically in advance of expected fly activity. However, the blowfly has shown an ability to develop resistance to some of these insecticides. Recent reports of the co-occurrence of resistance to both dicyclanil and imidacloprid in in vitro bioassays with field-collected fly strains has raised the possibility that the two resistances may represent cross-resistance linked by a common mechanism. We investigated this by imposing insecticide selection pressure on larvae of two insecticide-resistant field strains over a number of generations using either dicyclanil or imidacloprid and then measuring changes in sensitivity to both the selecting chemical and the alternate chemical. Larvae selected over six generations with each chemical showed significant increases in resistance to the selecting chemical: resistance ratios at the IC 50 5.5 - 8.1-fold higher for dicyclanil, and 3.1 - 3.8-fold for imidacloprid. The larvae also showed significant increases in levels of resistance towards the alternate chemical: resistance ratios 2.6 - 3.1-fold higher towards dicyclanil following selection with imidacloprid, and 2.2 - 3.2-fold higher towards imidacloprid following selection with dicyclanil. The increases in resistance to both chemicals after exposure to either suggests a common mechanism of resistance, at least in our laboratory-selected populations. Assays with the cytochrome P450 inhibitor aminobenzotriazole showed that this synergist was able to remove the increased resistance to both compounds in strains selected with either compound, suggesting that cytochrome P450 is responsible for the resistance observed to both chemicals. Our results confirm that cross-resistance exists between dicyclanil and imidacloprid in the sheep blowfly, and hence the two compounds should be considered as related entities in insecticide rotation strategies for flystrike control. • We imposed laboratory-based selection pressure on two field strains of the sheep blowfly. • Fly larvae were exposed to increasing concentrations of dicyclanil or imidacloprid for 6 generations. • Resistance levels increased to both compounds in flies selected with either of the two compounds. • Results indicate existence of cross-resistance between dicyclanil and imidacloprid. • Synergism experiments indicate role of cytochrome P450 in resistances to both compounds.

Source: Veterinary Parasitology

DOI: 10.1016/j.vetpar.2024.110326

Authors: Andrew C. Kotze, Angela P. Ruffell, Nicholas M. Rolls

Institutions: Commonwealth Scientific and Industrial Research Organisation, The University of Queensland, Agriculture and Food

Language: English

Topic: Insect Resistance and Genetics

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Zero hunger

Open Access status: hybrid

Estimated APC paid: $3,330