Review of the global status and recent development of insecticide resistance in field populations of the housefly, Musca domestica (Diptera : Muscidae)

Insecticide resistance of the housefly Musca domestica Linnaeus is reviewed covering the period 1977 to 1994. The review is based on published informa tion and on a large amount of information not generally available, because it was unpublished, only appeared in local reports, or for other reasons (e .g. language) was not included in the common bibliographic databases and ab stract journals. Information obtained by personal communication with collea gues all over the world has also been included. The common methods of testing and measuring insecticide resistance in house fly populations and strains, and of calculating the resistance levels by me ans of various susceptible reference strains are summarized and discussed. The sequential development and persistence of resistance in wild housefly p opulations on Danish farms from 1948 to 1992 are summarized and discussed, emphasizing changes since 1976 and including: resistance to organophosphoru s compounds in relation to selection pressure, depending on the mode and ex tent of application; resistance to pyrethroids from the 1970s due to the fr equent use of space sprays and involving homozygotic kdr and super-kdr fact ors; trials and use of insect development inhibitors; and persistence of in secticide resistance after cessation of insecticide use or relaxation of se lection pressure. The global status of resistance in M, domestica is reviewed according to cl ass of insecticide and geographical region. Even though the use of DDT and related organochlorine compounds has been banned for fly control for many y ears, resistance to DDT in houseflies still occurs almost everywhere, at le ast in a section of the housefly population. The significance of the uneven distribution of the kdr-factor in different regions of the world is discus sed. A variety of organophosphorus compounds has been used for fly control since the 1950s, and resistance to most of them has developed if the;election pr essure has been high, e.g. by use of residual sprays or frequent treatment of breeding sites. New data on resistance to organophosphorus compounds are reviewed and discussed in relation to the local use of these insecticides for housefly control. Resistance to aryl carbamates was found commonly in r egions where various organophosphates had been intensively used for housefl y control and was mainly due to cross-resistance. Resistance to oxime carbamates, particularly methomyl, has been rare, high resistance in houseflies having been reported only from a few farms in Denm ark and England, in spite of widespread use of methomyl baits in Europe and North America. The widespread development of resistance to pyrethroids reported since 1976 is summarized, especially the remarkable differences in the development of resistance between various countries or regions. The connection between th e occurrence of the kdr factor and the intensity of selection pressure with pyrethroids is discussed. Significant resistance to pyrethroids was common throughout Denmark and Sweden in the 1970s, in the UK in the 1980s and rec orded locally in Central Europe from 1979 onwards. In the Middle East no si gnificant resistance to pyrethroids was discovered until the 1990s. Similar ly no problems of pyrethroid resistance were found in extensive surveys of Japan and China in the 1980s in spite of widespread use of residual pyrethr oids. However, by the 1990s, pyrethroid resistance appeared to have become relatively common in both China and Japan, according to unpublished informa tion. The relatively few strains tested from 1978 to 1987 from South and We st Africa were all shown to be susceptible to pyrethroids, as were occasion al strains from South and Central America collected from 1983 to 1987 and f rom Australia in 1989. Residual pyrethroids were widely used in North Ameri ca from the 1970s, but reports of resistance were rather few in the 1970s a nd 1980s. First reports were from Canada in 1979, Georgia and California in 1984 and New York in 1987. However, by 1991, resistance to pyrethroids was considered to be widespread in the USA. During the period under review, only two insect development inhibitors, dif lubenzuron and cyromazine, have been widely used for fly control, either by direct application to breeding sites, manure, garbage, etc., or as an admi xture in feed for poultry or pigs. Widespread use of diflubenzuron or cyrom azine as direct treatment of manure has not led to resistance of practical importance except on a few farms in the Netherlands (diflubenzuron). Howeve r there are reports showing that the use of either compound mixed into feed has resulted in the development of moderate to high resistance to these co mpounds, and subsequent complaints of control failure(s) in the USA and Jap an. High resistance in adult flies to organophosphates and pyrethroids does not usually confer cross-resistance to the larvicidal effects of diflubenz uron or cyromazine, but cross-resistance between organophosphorus compounds and some juvenile hormone mimics, e.g. methoprene has been reported. The Bacillus thuringiensis beta-exotoxin has only been used on a limited sc ale for treating breeding sites of houseflies on farms, and no development of resistance has been reported. In the USA, moderate resistance to abamect in was found in field strains resistant to permethrin since 1989.