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Sheep blowflies |
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Calliphoridae, Scareophagidae and Muscidae - Various spp.
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Typical blowfly maggots
© Agriculture Western Australia
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Description
PRIMARY PESTS (initiate strikes on sheep)
Australian sheep blowfly (Lucilia cuprina)
The Australian sheep blowfly is the most important sheep blowfly species, causing up to 90 per cent of single species strikes. It is a metallic green blowfly a little over 10 mm long. It is distributed Australia-wide and is most abundant in autumn and spring. It only attacks sheep.
Western Australian brown blowfly (Calliphora albifrontalis)
The Western Australian brown blowfly is the second most important blow-fly species causing up to 15 per cent of single species strikes. It is a robust golden-brown blowfly, up to 13 mm long. Its distribution is restricted to the south-west of Western Australia and it is most abundant during winter and spring. It commonly breeds in carcasses.
Lesser brown blowfly (Calliphora dubia]
The lesser brown blowfly is rarely involved in single species strike, being recovered most frequently in combined strikes. It is a yellowish blowfly with a purplish stripe on its abdomen. Its size is variable ranging from 5 - 10 mm. It occurs throughout the southern half of Australia and is basically active during summer through to autumn, It commonly breeds in carcasses.
SECONDARY SPECIES (require the presence of a primary species before they can strike sheep.)
Hairy maggot blowfly (Chrysomya rufifacies)
The hairy maggotblowfly isthe mostimportant of the secondary species. Its large hairy maggots can sometimes cause death of a sheep in a relatively short time. It is a green metallic blowfly with dark blue margins to its abdomen and is some 10 mm long. It occurs Australia-wide, and is mostly active in summer through to autumn. It commonly breeds in carcasses.
Flesh fly (Sareophagidae)
The flesh fly is the second most important secondary species; however, it rarely causes death of sheep. They are large greyish black flies which have a distinctive striped thorax, and an abdomen which is boldly chequered with a black and lighter pattern. They are common throughout the sheep rearing areas showing greatest abundance in summer. They readily breed in carcasses and manure.
Tertiary species (strike sheep even later than the secondary species)
Black carrion fly (Hydrotaea rostrata)
The black carrion fly commonly strikes scabs of old and partially healed wounds. It is a dark bluish black native fly about the same size as a housefly. It is found Australia-wide in summer and spring. They are common breeders in carcasses.
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Primary species(Calliphoridae)
© Agriculture Western Australia
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Life cycle
The sheep blowfly problem is a result of the sheep's fleece providing a suitable environment for the blowflies to lay their eggs and complete the larval stages of their life cycle. Under normal rearing conditions eggs hatch in 8 - 12 hours; maggots take three to four days to reach full size and pupate one to two days later. Adults hatch from the pupa after six to eight days and are capable of laying eggs five days later. |
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Secondary and Tertiary species
© Agriculture Western Australia
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Damage
In Western Australia conditions are suitable predominantly during autumn and spring for the development of flystrike on sheep. Fleece conditions attract blowflies which lay eggs which then hatch as maggots. Blowfly maggots developing on sheep can cause a reduced wool clip and a general loss of condition sometimes resulting in the death of the sheep. |
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Initial stages of flystrike
© Agriculture Western Australia
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Control
In Western Australia breech strike has been controlled by the adoption of the radical Mules operation with optimum tail length; and by crutching and drenching at strategic times and by suitable grazing management. However, the prevention of body strike still relies on adequate jetting with insecticides. Sheep are at risk from breech strike if the breech area is soiled with dags and urine stained wool. Body strike occurs almost exclusively on sheep suffering from dermatophilosis (dermo or lumpy wool) or fleece rot. The most practical blowfly control strategy is an integrated one, in which management practices (including crutching, shearing, etc.) and the timely application of insecticides are all important for the prevention of body strike on sheep. To obtain maximum benefit from using insecticides, it is important that they are applied adequately. The insecticide must penetrate the fleece to the skin, and be uniformly distributed throughout the target areas. |
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