Eradication of warble flies in West Germany

Since derris preparations applied in compliance with a government directive of 1933 failed to control warble flies, a new law to enforce treatment with systemic insecticides was passed in the Federal Republic of Germany in 1967. Under this law, the owners must treat their cattle with systemics before the grazing season starts if hypodermal grubs are found on even a single animal in the herd. The law authorizes state governments to decree that all cattle in a state or in certain regions be treated at a certain time. All states with pasture areas have exercised this right.The grazing season runs from May to October and the cattle are stabled thereafter. The treatment period is mandated after the grazing season, at the beginning of December. If warbles are observed before the cattle are turned out to pasture, a second treatment of all the cattle on the farm is mandatory. Through this procedure, warble infestation has been greatly reduced. In some areas, the infestation has been eradicated completely and is not seen either on live animals or on the hides of slaughtered cattle. The level of infestation at which it is safe to abandon autumn treatment without risking a resurgence of the infestation has not been determined.