Development of a changed response in Lucilia cuprina (Wied.) to organophosphorus insecticides in New South Wales

Abstract

Since 1956, samples of Lucilia cuprina (Wied.) from many parts of New South Wales have been tested annually for signs of resistance to organophosphours insecticides, which are used there to prevent fly-strike in sheep. For tests, 0.1 μg. diazinon per fly was applied topically; this discriminating dose was twice that required to kill 100 per cent. of susceptible flies. In 1965, some of the flies in a sample from Dubbo, in central-western N.S.W., survived the discriminating dose. Sensitivity tests of the progeny of the survivors (DB strain) and of a normal susceptible strain revealed that the LC50 of the DB strain was about three times that of the normal one. Further tests established that a roughly similar change in sensitivity had ocurred to other diethoxy (dichlofenthion, fenthion-ethyl, bromophos-ethyl, parathion) and to dimethoxy (fenchlorphos, parathion-menthyl, bromophos) organophosphors compounds. The change was therefore non-specific and, since it was also small, is regarded as an example of tolerance rather than of resistance.Subsequent field surveys in 1965–66 showed that tolerance of L. cuprina to diazinon was widespread in N.S.W. The possibility that resistant strains will be selected out by continued use of organophosphorus insecticides is discussed.

Relative efficacy of organophosphorus insecticides against susceptible and resistant strains of the strike blowflyLucilia cuprina(Calliphoridae) in New Zealand sheep

“…In Australia, diazinon resistance was detected in 1965 in L. cuprind 13 ). It is likely that L. cuprina entered New Zealand from Australia, so it is not surprising that New Zealand strains are also resistant<S).…”

The genetic basis for organophosphorus resistance in the Australian sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera, Calliphoridae)

“…Periodic screening tests by the New South Wales Department of Agriculture on field samples of L. cuprina for OP-resistance detected no change in response until 1965 when a survey covering many districts in N.S.W. revealed a low-order ' tolerance' to OP-insecticides (Shanahan, 1966;Shanahan & Hart, 1966). These authors concluded that the protective period was not reduced significantly by the increased tolerance as long as insecticide application was thorough.…”

Resistance to two organophosphorus insecticides in New Zealand populations of the Australian sheep blowfly, Lucilia cuprina

“…In Australia L . cuprina has developed resistance to representatives of several groups of insecticides including cyclodienes (dieldrin, aldrin; Shanahan, 1959), carbamates (butacarb;Hughes & McKenzie, 1987) and organophosphorus compounds (diazinon; Shanahan, 1966). One of the earliest available organophosphorus (OP) flystrike preventives was diazinon.…”