Combating the Sheep Blow-fly

New Zealand Journal of Agriculture, Volume 60, Issue 1, 15 January 1940, Page 49

Combating the Sheep Blow-fly

REPORTS have been received that ' lambs have been found affected with maggots as a result of strike by the sheep blow-fly or maggot-fly. . Although . several flies . are . blamed, the small yellow-brown hairy species, . and less commonly the bronze-green species,- are mainly responsible. The

blue bottles and the striped field flies do not blow living sheep. Weak, backward lambs which have been scouring appear to be more susceptible to the fly. Scouring, daggy lambs are likely to have the region of the breech badly stained with urine and urine stain, and the results of skin irritation from the stain, appear to be very attractive to the egg-laying fly. A single fly may deposit as many as 1000 eggs in a single day, so that a very small number of flies' may do a large amount of damage. Prevention Precautions consist mainly of the prevention of the conditions which are attractive to the egg-laying flies. Dagginess in lambs, therefore, requires to be attended to by an early crutching in late December or early January, or at any time when the fly is active. The dagginess may result from-a change in the feed in wet weather, or later on may result from scours due to worms in the lambs. In any case, the cleaning up of the lambs and hoggets will do a very great service in controlling the conditions which attract the fly, and which result in the common breech strike so often seen in lambs. Body strike and back strike in areas where they are prevalent are more difficult to control, and’ are probably best dealt with by using an arsenical spray. . •. ; .. ' : . ! . .. Treatment In the treatment of affected lambs, the wool should be shorn around the “struck” area, and all maggots must be killed and removed. A good, but rather expensive, dressing for the wounds may be prepared by heating 31b of boric acid in one gallon of pure glycerine, stirring until the mixture is clear. To this may be added one quart of ethyl alcohol, which dilutes the glyceroborate. improves the lotion, and cheapens its preparation; This preparation is effective in killing the maggots, is non-irritant, assists the healing of the wound, and has , a protective value for some time afterwards. Cheaper dressings may be used, such as a 5 per cent, solution of zinc sulphate in water, or 4 per cent, phenol crystals'in whale oil. A 2 per cent, solution of liquid carbolic sheep dip

or similar disinfectant : material is effective in driving out maggots and in sterilising the wounds, but it is best to follow up with an oily dressing. ' A change of paddock may sometimes lessen the amount of strike, as owners frequently state that the fly appears to be more active in certain shady paddocks or paddocks with steep faces and gullies.

Disposal of Carcasses Needless to say, all dead animals should be burned or deeply buried. If the carcass is not buried deeply the maggots will escape., If it is impossible to burn or bury, it might be possible to saturate the carcass thoroughly with an arsenical solution to poison the maggots as they hatch 'out and feed. To reduce . the breeding ■ ground of the fly is, and , always will be, the most efficacious measure against blow-flies.