The prevention and treatment of blowfly strike in sheep : report no. 2 / by the Joint Blowfly Committee (Appointed by the Council for Scientific and Industrial Research and the New South Wales Department of Agriculture).

Date:
1940
Catalogue details

Licence: In copyright

Credit: The prevention and treatment of blowfly strike in sheep : report no. 2 / by the Joint Blowfly Committee (Appointed by the Council for Scientific and Industrial Research and the New South Wales Department of Agriculture). Source: Wellcome Collection.

    40/52 (page 38)
    IV. MEASURES TO REDUCE FLY ABUNDANCE. Before discussing means of reducing fly abundance, it must be clearly understood which flies are enemies and which are not, for, obviously, the destruction of flies which never attack living sheep cannot reduce the amount of strike. In the report No. 1 of the Joint Blowfly Committee*, the species of flies commonly involved in strike are illustrated in colour and are described on pages 11-14. The flies are divided there into three series— primary, secondary, and tertiary. The primary flies are those which will start a strike single-handed, so to speak; the other two groups merely follow on and infest the wound made by the more enterprising pioneers. Among the primary flies, the green-bottle—Lucilia cuprina— is the arch offender, the brown blowflies (the Calliphoras) taking second place as initiators of strike.t Among the secondary flies, Chrysomyia rufifacves, a green fly, which is quite often confused with L. cuprina, is the most important. If compared carefully, it will be seen that Chrysomyia rufifacies is a more thick-set fly and tends to have a bluish-green colour, whereas L. cuprina is a more slenderly-built fly and tends to a bronzy- -green shade. From studies carried out over the last ten years in Canberra and elsewhere, certain definite facts can be stated— (1) Strikes only occur when primary flies are present in considerable numbers. (2) By far the most important primary fly is LZ. cuprina. (3) An increase (or decrease) in the abundance of L. cuprina, as recorded by regular trapping, shows a_ general correlation with a rise (or fall) in the incidence of strike. (4) Chrysomya rufifacies seldom, if ever, initiates a_ strike, although in company with primary flies it will produce very serious ones. It follows, therefore, that attempts to reduce fly abundance must be directed systematically against the primary flies and, in particular, against L. cuprina. The primary flies may be attacked either in the adult or in the maggot stage. Adults may be trapped or poisoned, and maggots may be destroyed in their breeding grounds, viz., carcasses and struck sheep. 1. Traps and Poison Baits. Carefully planned experiments{ have shown that extensive use of traps will reduce the incidence of strike by over 50 per cent. In these tests, however, the trapping was done on a scale hardly likely to be of practical application. The average distribution of traps was one to about 25 acres, but the concentration varied somewhat in the different sets of experiments. In one, in which no less than 46 traps were used to protect a 480-acre paddock, the strike incidence was one-third of that in the control paddock completely unprotected by traps. It seems clear, then, that the present methods of trapping do not provide economical control of strike. —_——— ~— * Reference 2], p. 42. + Reference 23, p. 42.