Comparative ability of hybrid and homozygous resistant larvae of Lucilia cuprina to cause strikes under experimental conditions.

The intervals between the jetting of sheep with dieldrin or BHC, and the inducement of flystrike by implants of hybrid and homozygous BHC/dieldrin resistant larvae of Lucilia cuprina, were compared. Flystrikes soon established with homozygous resistant larvae, but considerable protection was afforded against hybrid larvae, the interval being longer with BHC than with dieldrin. Dieldrin was shown to have a residual effect on rr larvae in a mixed population 9 weeks after jetting. It is suggested that wide adoption of mulesing and mid-season's crutching would favour reversion to susceptibility in the blowfly and thus extend the field life of insecticides to which resistance has emerged.