Jl. Yen et al., PREDICTING RESISTANCE AND MANAGING SUSCEPTIBILITY TO CYROMAZINE IN THE AUSTRALIAN SHEEP BLOWFLY LUCILIA-CUPRINA, Australian journal of experimental agriculture, 36(4), 1996, pp. 413-420
Four cyromazine-resistant variants of Lucilia cuprina were selected af
ter ethyl methanesulfonate mutagenesis and screening above the concent
ration of cyromazine lethal to susceptibles. Resistance is controlled
by a single gene in each variant. Two resistance loci have been identi
fied, one (Cyr 4) closely linked to the marker 'reduced eyes' on chrom
osome IV, the other (Cyr 5) closely linked to the 'stubby bristles' ma
rker on chromosome V. Concentration-mortality line analysis shows resi
stance ratios are low (1.5-3x). One variant [Cyr 4(2)] is viable as a
homozygote, the others are lethal [Cyr 4(1)] or, at best subvital [Cyr
5(1) and Cyr 5(2)]. Competition experiments between resistant heteroz
ygotes and susceptibles show that resistance to cyromazine is selected
for over a limited range of concentrations. The capacity of laborator
y studies to predict likely resistance mechanisms before they evolve i
n the field is discussed. The use of genetic, toxicological and relati
ve fitness data arising from these studies to devise the most effectiv
e strategies of insecticide usage while minimising the evolution of re
sistance is emphasised.